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           DISCOURSES






ECONOMICAL & PHILOSOPHICAL,





            DETAILING





 THE PROPERTIES OF MATTER.
\ 
 
PLAIN DISCOURSES   <f>/^
LAWS OR PROPERTIES  OF MATTER:
CONTAINING
THE ELEMENTS OR PRINCIPLES
 MODERN CHEMISTRY;
                    WITH
MORE PARTICULAR DETAILS OF THOSE PRACTICAL PARTS
             SCIENCE
     MOST INTERESTING TO MANKIND,
                     AND
       CONNECTED WITH DOMESTIC AFFAIRS.
      Addressed to all American promoters of useful knowledge.
                ■■«>—<>■"< c >••••<»—«>----
By THOMAS EWELL, M. D. of Virginia.
       ONE OF THE SURGEONS OF THE UNITED STATES NAVY.
<>--<►- ~* C >....«>—<»—
   " Humanity sitting at the portal of misery, through the medium of
Science implores relief, while a tear is dropt for the unfortunate children
of men."________________________________________________________.
                 NEW-YORK:
 PRINTED FOR BRISBAN ff BRANNAN, 186 PEARL-STREET.
                 Daftis, Printer,
                    1806. 
\
               \+. .
DISTRICT OF NEW-YORK, ss.


                        ijE it remembered,  that on the
                        twenty-third day of July, in the
                        thirty-first year  of the Indepen-
         (L.  S.)         dence  of the  United States of
                        America, James Brisban and John
                        Brannan, of the said District, have
                        deposited in this office the title of
                        a Book,  the right whereof they
claim as  proprietors,  in the following words, viz.  " Plain
" Discourses on the Laws or Properties of Matter; containing
" the Elements or Principles of Modern Chemistry, with more
"particular Details  of those practical parts  of the Science most
" Interesting to Mankind, and connected tuith Domestic Affairs.
" Addressed to all American promoters of useful knowledge.   By
" Thomas Ewell,  M. D. of Virginia.   One of the  Surgeons
" of the United States Navy.  f Humanity sitting at the portal
" of misery, through the medium of Science implores relief, •while
11 a tear is dropt for  the unfortunate children of men.1"  In con-
formity to the Act  of the Congress of the United States,
entitled, " An Act  for the encouragement of Learning,
" by securing the  copies of Maps,  Charts  and Books to
" the Authors and  Proprietors  of such copies  during the
" times  therein mentioned," and also to an Act  entitled,
" An Act supplementary to an  Act, entitled, « An Act
< for the encouragement of Learning,  by securing the copies
' of Maps, Charts  and Books to the  Authors and  Proprie-
* tors of such copies during  the times  therein  mentioned,'
" and extending the benefits thereof  to the arts of Design-
" ing, Engraving and Etching Historical  and other Prints."
            EDWARD  DUNSCOMB,
                       Clerk of the District of New-2~ork. 
                    TO

THOMAS JEFFERSON, Esq.
             OF VIRGINIA,
  THE PRESIDENT OF THE UNITED STATES OF AMERICA.

SIR,
     TO inscribe this work to you, I was in-
cited by an impulse given from a  view of your
station, as well as  a sense of favors receiv-
ed.  Raised  by  your own qualities,   and the
will of a free people, to the first place among
them,  the legitimacy of your title will be  ques-
tioned by none.
   IN preparing the following plain discourses,
I was stimulated by a desire to  imitate you in
doing good.  I  was  anxious  to revolutionize
the habits of many of our countrymen; to lessen
their difficulties, by acquainting them with im-
portant improvements,  and  to  diffuse  more
widely that genuine happiness derived from the
 interesting study of the ways of nature.
   TOU, sir, have long since enjoyed the lux-
 ury of serving your countrymen.
    WITHOUT expressing sentiments concern-
 ing your  services as a  statesman,  in affairs
 better suited  to my opportunities of observing,
$e>i<i 
 6            DEDICATION.
 I perceive that you have been useful to your
 country.   With a  benevolence without bounds,
 the scenes of elevation and pleasure could not
 prevent your sympathizing with the sorrows of
 those groaning in the retired walks of life.
 Tou have been foremost in setting the exam-
 ple of introducing  in  society  improvements in
 various arts.  Such as  have  engaged in use-
ful innovation under your notice, feelingly tell of
 the generosity of your patronage.   Many of the
 rising generation owe their prosperity to that li-
 berality  of sentiment  so  seldom met with,  but
 which  has so often led you to favor  the young.
 To  a  virtuous mind  it  must be pleasing to
 reflect, that  the thankful will long bear in re-
 membrance your parental goodness.   In future
 days they will emulate  each  other,  in  the
 celebration of your worth, while you are associ-
 ated among the benefactors of mankind.
    THAT your happiness may be equal toy our
 services, and that your successors may imitate
 the mildness and wisdom  displayed during your
 career, are among the sincere wishes  of
            Tour Respectful and
                  Obliged Servant,
                       THOMAS  EWELL. 
PREFACE.
     THE following plain work I prepared with
a view to  lessen the difficulties, and to increase
the conveniences of the  citizens of the United
States, by introducing them to a more intimate
acquaintance with chemistry, or the qualities of
the substances around them.  The immense ad-
vantages which will result from the general diffu-
sion of such knowledge, are glanced  at in the
introductory discourse. These advantages, 1 have
indulged  in  the hope,  will lead the respect-
able farmers and artists, the benevolent editors of
publications,  particularly the teachers  of semi-
naries, my brethren of the medical faculty, and
the intelligent of every denomination, to favor
and promote the undertaking.  As expressed in
the title page, the work will contain  a general
account of the laws or properties of matter, with
more particular details of the  most useful and
interesting parts of the science, in a language
adapted to the comprehension of common un-
derstandings.  I designed to lessen the number
of technical terms in this elementary work, by
excluding all such as are of no importance, and
such as relate to the less valuable refinements of
-chemistry, which could  only be gratifying to
professional and very learned characters.  The
terms which are introduced, I have endeavor- 
8
PREFACE.
 ed to render as intelligible as possible.  It was
 expected that this would so lessen the difficulty
 of learning the most important branches of che-
 mistry, as no longer to prevent the majority of
 the people from engaging in  the  pursuit.   To
•persons of sound sense, it must at once appear,
 that the best method of inducing others to study
 a science, is to render it as simple as it can  be.
 Hence it must appear highly  improper, that so
 many elementary books are crowded with a  pa-
rade of words. The following extracts of letters
with  which I was favored from the President,
and  from the honorable  Bushrod Washington,
may not be improperly introduced in this place.

                    " MONTICELLO, AUGUST 1805.
   " OF the importance of turning a knowledge
of chemistry to household purposes, I have been
long satisfied. The common herd of philoso-
phers seem to write  only  for one another. The
chemists have filled volumes on the composition
of a thousand substances of no sort of importance
to the purposes of life; while the arts of making-
bread, butter, cheese, vinegar,  soap, beer, cider,
&c. remain  unexplained.  Chaptal has lately
given the chemistry of wine making;  the late
Dr. Pennington did the same as to bread, and pro-
mised to pursue the line of rendering his know-
ledge useful to common life;  but death depriv-
ed us of his labors.  Good treatises on these sub-
jects should receive general approbation.
                    " TH: JEFFERSON." 
PREFACE.
9
                 " MOUNT-VERNON, 13th SEPT. 1805.
   " I have long thought that a work upon the
 plan  you suggest, was much wanted  by those
 who form the great bulk of readers on chemical
 subjects.  I have not  met with a single treatise
 which has  not appeared unnecessarily obscured
 by technical terms, which only scholars can un-
 derstand.  They have been more generally ad-
 dressed to  the  comprehension  of professional
 and learned men,  than to those of the humble
 walks of life;  for whose use this science might
 be made most essentially  to contribute, by a-
 dapting it  to their capacities, and by pointing
 out the way by which its principles may be ap-
 plied  to the more common arts, in which they
 are daily employed.  You will I think do great
 good  to society and much honor to yourself, by
 executing such a work as you propose. My best
 wishes will accompany you in your labors, and
 I shall be happy to aid them as  far as I can.
                 « BUSH. WASHINGTON."
   CHEMISTRY must be considered as an art
and  as a science.  As an art,  it  was coeval
with the earliest labors of man; but, as a science,
it was unknown  to our ancestors.  Indeed, on
taking a view of the  researches of chemists in
former times,  we  find considerable cause  for
complaint.   The interests of mankind suffered
shamefully by their neglecting chemistry as a
science for so many ages.  Moreover they acted
so  extravagantly as to disgust those with the pur-
suit from whom improvements might have been
expected.  For ages they professed to  be ac-
                     B 
10
PREFACE.
quainted with many of the operations of nature,
and pretended to communicate their knowledge
by certain signs, or hieroglyphics,  which only
a few could comprehend.  They afterwards lost
much time in  ridiculous efforts to discover  the
art of transmuting metals, or converting the com-
mon ones into gold.  These  alchymists (for so
they were called) long labored to discover me-
dicines to cure all disorders, and secure immor-
tality on earth.  Some of  them had the effron-
tery to announce, that in consequence  of hold-
ing a converse with  God, who imparted such
secrets to his favorites, they could readily suc-
ceed in such wonderful acts.  The brilliancy of
some of their processes, striking the more forci-
bly from their fanciful manoeuvres, was such as
to excite as great  curiosity as  the amazing ex-
ploits reported in the days  of chivalry.  Dazzled
and deluded by them, the credulous spectators
admitted the assertions of these impostors, con-
fided in their statements, looked on  them with
awe, and successively became dupes to their de-
signs.  Many,  even in the middle of the  16th
century, credited these alchymists,  till a fatal
blow was given to such impositions by the time-
ly  death of their  enthusiastic Paracelsus, who
declared, that  by virtue  of his  medicines he
would live  for ever.  The death of  this  deluded
wretch, was followed by  the complete down-
fal  of  the chemists over all  Europe; and for a
long time so contemptible was their character,
that it was deemed disgraceful  to be  called a
chemist. 
PREFACE.              11
   IN a state of darkness and contempt, chemis-
 try continued to be held, until men embraced
 the science whose expectations were reasonable.
 Towards the  last of the  16th  and commence-
 ment of the 17th centuries,  respectable gentle-
 men  engaged in the  study, made interesting
 discoveries, and partly restored the science to its
 proper rank.   But they did not quite succeed;
 for instead of noticing facts and making infer-
 ences from these, they indulged in  conjecture.
 The doctrine of the formation of all bodies from
 air, fire, and  three  or four  other  supposed ele-
 mentary bodies, was then  delivered, in all the
 fulness  of philosophic confidence,  with many
 other notions alike  not founded  on fact.  For
 this, however, a remedy has lately appeared.
 A few years since men of the first talents advan-
 ced and created a revolution in the literary world.
 Animated by a love of truth, they embraced the
 science of chemistry, and in the embrace gave
it new importance. Their discoveries have con-
founded the conjectures of predecessors;  they
have taught mankind the folly of their prejudi-
ces against chemistry,  and they have revealed
 the proper objects of the science.  Some of our
infant country have aided in the glorious refor-
mation and establishment. The celebrated che-
mist, Dr. Mitchill of the United States senate,
has made some  ingenious  suggestions in the
Medical Repository  of New-York;  a work
conducted by himself, and the not less learn-
ed and accomplished Dr. Miller. The accurate
experimenter, Professor Wopdhouse of  Phi- 
12
PREFACE.
ladelphia, and the learned Dr. Mac Lean of
Princeton College are among the foremost on
the list of chemists in this country. It is from
the interesting lectures of these  respectable
characters, that many of the rising generation
have received a love for chemistry.
  ALTHOUGH it be true  that modern che-
mists have been of great service, yet it is equal-
ly so, that the value of some of their labors, has
been lessened by a too active spirit of innova-
tion.   This has led them to introduce, unne-
cessarily, terms from the dead languages; and
to make too many divisions and subdivisions in
their works, which are directly at war with the
uniform simplicity of nature.  While writing
these discourses, if I studied at all, I studied
to avoid such extremes. However, as should be
expected, I availed myself of the writings of the
best chemists. When conscious of an inability
to improve, I imitated their manner of stating
facts. To the systems of chemistry by Thomp-
son, Chaptal, Murray, and particularly  that
by Mr. Accum, I am indebted.  The copious
extracts from this last  author will  much in-
crease  the value of this work.   But  I have
not been a very servile imitator.  It will be
 found that I have advanced  something new on
 the subjects of heat, light, electricity, vege-
 tation, manures,  and  also on several other
 branches of chemistry.  Such original obser-
 vations are introduced from the belief that
 they were  correct.   They  served to impress
 me more forcibly with a great man's remark, 
PREFACE.
13
that " Truth is not hidden, it lies on the sur-
face."   Even if I have missed it on the sur-
face, allowances will be made, when his con-
sidered, that the chief part of my  time has been
devoted to my favorite pursuit after a  know-
ledge of the practice of physic ; and that with
a view to turn the attention of others to che-
mistry^  I prepared this work in those  leisure
hours which young physicians have,  in con-
sequence of the too common belief, that the
success of the healing art depends not so much
on the application of principles to practice, as
on experience, or  something like  sleight of
hand.   It will be found  that the most  ma-
terial doctrines I have proposed are extensions
of the principles relating to  operations in animal
bodies, which were advanced in my Inaugural
Essay,  published during  my attendance  on
the hospital in Philadelphia, 1804, and which
were supported by the approbation of Dr. Rush
and other gentlemen of the faculty.  This ser-
ved to increase the confidence with which I ven-
tured to introduce them in  this book.  The at-
tention I have paid to each subject was regula-
ted by its known importance; and I have  stu-
died brevity to avoid fatiguing the reader.
   IT was deemed unnecessary to give  the bi-
ography of  the celebrated chemists, although
it be common for systematic  authors to do it.
The pleasure of making  a discovery  was a
sufficient reward for innovators,  who,  if pro-
perly philanthropic,  wished posterity to learn
their improvements, before they read accounts 
14
PREFACE.
 of their lives.  Nor  have I thought proper
 to crowd the pages with the names of authors
 while mentioning their discoveries,  or to notice
 the  many  erroneous theories and conjectures
 which have been obtruded on the  world;  oc-
 casionally, however, I have been obliged,to
 hint at some of them.
   THE table of contents will serve as an in-
 dex  to the  work.   Definitions of such words,
 as were unavoidably introduced, are  given at
 the end of the discourses, in order that if their,
 meaning be forgotten, or if there be  some who
 wish not to be at the trouble of reading more
 than one or two parts, they may understand
 them with least difficulty.
   IT would not be proper for me  to  omit
 acknowledging my obligations to the accom-
 plished  scholar  and Secretary  of  the Navy,
the Hon. Robert Smith,  and also  to Judge
Washington,  the  benevolent   Mecsenas  of
 Mount Vernon.  They gave me that patro-
nage which enabled me the better to progress
in this undertaking.  It is pleasing  to reflect,
that such characters have always a reward for
their friendly  exertions, in the delight they
take in so acting. 
INTRODUCTORY ADDRESS. 
I 
INTRODUCTORY  ADDRESS.
ARTISTS, FARMERS, Sf FELLOW-CITIZENS,

     I HERE offer you a work, prepared to render you better
acquainted with chemistry, or the properties of that matter
amidst which you are placed. By the important promotion
of your own interests,  by the  high delight I shall derive
from being instrumental in serving you, I pray you to read,
to think, to dwell on the researches of chemical philoso-
phers.  In the view of these researches, which I am about
to give, defects may be noticed.   To  screen me from the
condemnation of the censorious,  I  have to  entreat you to
consider my intention  as a cover to what will be commu-
nicated, and to allow the performance to rest on that good,
which must result from a  general attention to the facts and
principles it will contain.

    MUCH indeed is it to be lamented, that so considerable
a part of the community seldom think for themselves, or are
in the least  aided by the labors of their forefathers.   Not-
withstanding the truth proclaimed in all ages, that the plea-
sures are derived from the actions of life, yet we frequently
find persons who persist in idleness;  who will not endea-
vor  to  be benefited by the experience of those who  lived
before them.   It is in consequence of not taking due advan-
 tage of the  improvements of philosophers,  that the greater
 part of the people are in  situations  loudly calling fora-
                            c 
IS          INTRODUCTORY  ADDRESS.
mendment.   From  this, it is now particularly incumbent',
on such as are intelligent, to be  active in disseminating use-
ful knowledge.   Every citizen,  regarding the welfare of his
species, should strive to increase the dispositions to think,
and to combine  researches for  knowledge, with labors for
maintenance.  By this, many would  become qualified for
acting more  usefully, and  much  time would be spent a-
greeably,  which is otherwise lost in  sloth,  or  in devising
schemes for low amusements.

   OF the sciences which should be universally learnt,  che-
mistry ranks among the  first. Since its object is to instruct
us in the  qualities  of those bodies surrounding us, where
can limits be set to its value ?   How interesting should it be
to every individual! Surely the  friends of  humanity should
be industrious in imparting, to all classes of people, the
blessings which  may be derived from such an inexhaustible
source*

   THAT man, ignorant of the laws regulating  the sub-
stances around him, or if he only acquire the inconsiderable
knowledge afforded by his own  experience  and observation,
i6 very far from a desirable state.   He resembles a  traveller
in a  strange country, who,  if possessed  of  feeling,  pain-
fully progresses  in  consequence of  fears  concerning the
propriety  of his advances.   His  mind  is so disturbed by
difficulties,  that he  is entirely  prevented from enjoying the
fair prospects presented on the road.  The cautious passen-
ger through this world, to  avoid  such wretched  states of
uncertainty and hesitation, should early learn the properties
of those bodies, with which he will have so much to deal. 
           INTRODUCTORY ADDRESS.        19
In the time in which he is learning a few  of their proper-
ties, which he often does without knowing that he is learn-
ing chemistry, he could treasure up far more information by
studying the science systematically.   What is of more im-
portance, this knowledge would increase his independence,
and might enable him to perfect, at least highly improve the
improvements of his  predecessors.  No  one will doubt
this, when it is considered that although the science of che-
mistry has been  studied properly only for a  few years; and
although but a small  part of  mankind have attended to it,
yet a  progress has been made,  which astonished the world !
Who  could have believed an age ago, that chemists would
thus early have been able to decompose the air we breathe,
or the water  we drink, and  form  them again !  that they
would have proved diamonds to be simply consolidated char-
coal ;  that they  could have converted flesh into spermaceti
and saltpetre; or that they could  have made many other
discoveries which have amazed and delighted  the  greatest
men within a  few years ? In order to form a correct idea of
the importance  of chemical knowledge, it will  be neces-
sary to glance  at some remarkable facts;  and at  the con-
nexions of the sciences with those arts on which our lives,
comforts and luxuries materially depend.

   THAT minds are much under the influence of art, that
it is from education they receive their habits of action, will
be admitted by all.   On the truth of this,  is grounded the
practice of accustoming youths to that kind of thought most
useful to society.   Amongst the various kinds of mental
action,  there  are none of more consequence,  than the ex- 
 20        INTRODUCTORY ADDRESS.

 ercise of the judging and reasoning faculties.  Now the
 principles of  chemistry are inductions  from facts, obvious
 to the lowest comprehension.   In acquiring a knowledge of
 them, the facts are presented to us,  and the inductions are
 determined on by the judgment.  The reasoning faculty  is
 exercised in  comparing and  arranging the facts and infer-
 ences or  inductions.   By this the judgment and reason be-
 come improved; the habit of intellectual action is extended,
 and  it aids in the  investigation of truth on many subjects.
 With propriety we  may  therefore conclude,  that, if the
 science  of chemistry were  more generally studied, there
 would be less foundation for the remark of. Swift, "  that
 man was a rational though not a reasonable animal."

  THE  pleasures directly  derived  from chemistry,  are
 inferior to none in degree or duration.  Its sources yielding
 delight to the inquiring mind, are great and inexhaustible.
The man acquainted with this science, has wide fields for
enjoyment where least expected by the  vulgar.   To his  eyes
 no bodies appear disorganized, deficient in action, or devoid
 of interesting qualities ;  even in the  most inconsiderable
 objects he discovers beauties.  The eruptions of volcanoes,
earthquakes,  meteors, and  all the grand operations of na-
ture,  cease to excite in him that horror and dismay,  dis-
turbing the quiet of less thoughtful persons.   In such pro-
 cesses,  he perceives  simply the exercise of   the immu-
 table  laws of matter, which,  while  they announce  the
 wisdom of the  Creator,  produce in him the purest philoso-
 phic devotion.  Through the medium of matter, he learns
 the will of his Deity, and by this he is enabled, as  Mr. Chaptal
 observes,  to imitate the Creator in forming and decompo- 
            INTRODUCTORY  ADDRESS.         21
 sing bodies, and in predicting results with absolute certainty.
 And say, ye  experienced chemists!  what sensations ever
 seized your souls, so rapturous as  those,  felt  on finding
 yourselves able to revolutionize  the state of airs  and solids!
 to regulate at pleasure powerful elements,  the former sour-
 ces of destruction and terror! You will also testify, that it is
 gratifying  to  learn the composition  of bodies  yielding a
 support and their connexion with each other,  as well as
 the  causes of  the various  changes,   which  take  place
 in nature.   After once feasting on the pleasures resulting
 from such researches, but few would relinquish them, for
 the  fruitless pursuits  of most of the people.

   PERHAPS, too, at the closing  scene of life,  the  philo-
 sophic chemist may be  rewarded by pleasurable  thoughts.
 Unlike the many souls which seem  shattered at the prospect
 of  having  their bodies changed  into  putrid masses,  and
 mingled with the earth, he may reflect  on  the new process
 with calmness and  delight.   Instead of trembling on find-
 ing his extremities losing their genial warmth, and growing
 dark with livid  fluids ;  instead of giving way  to shrieks
 and lamentations, while his  perception is failing, his mind
 may be amused in contemplating the exercise of the laws
 of his visible body,  until it takes a final departure for en-
joyment  in other  scenes.

  SUCH considerations, however, are inferior  to  those
 arising from an adversion to the immediate good, which che-
 mical information will be of  to important arts.  It will en-
 able most artists  to extend the scale of their usefulness in a
 great degree.  To form correct conceptions  of  this,  we 
 22        INTRODUCTORY ADDRESS.
 will here glance at those arts with  which chemistry  is
closely connected ;  and first of the most noble  pursuit of
 man, the cultivation of  the earth.

   AGRICULTURE  is  most intimately  connected with
chemistry.  The power of seed to attract and unite to parts
of the soil, so as to vegetate or increase in bulk, is purely
chemical.   Chemical  knowledge  will teach the gardener
and farmer, what particular  soil is best adapted for parti-
cular seed;  it  will teach the way of forming soils for foreign
plants; of making manures to the greatest advantage; of
preserving  grain,  roots,  &c.  of  destroying  the insects,
and of correcting the disorders injuring the valuable shrubs.
In consequence  of  the  ignorance of most farmers on this
subject, they frequently blunder in a manner highly preju-
dicial to their interests.   Sometimes they not only spread a
particular manure, where  it can be  of little service,  but
they will use  it in a  state in which it is least valuable.   The
truth of this  assertion is shown by the fact, that most ani-
mal  substances  may  easily  be changed into  saltpetre;
which is an article universally  known  to  be an important
manure;  yet  this is seldom or never done in this country.
The wealth and  independence  of farmers, might also be
increased by  using many articles commonly thrown  away.
The  ashes of  the  corn stalk,  yielding potash  for  soap,
 and those of tobacco,  yielding  saltpetre,  confirm this re-
 mark.

   BUT  such immediate advantages do not seem the limits
 of what the  agricultural chemist should expect.   The  days
 I hope are approaching, when  industrious man, happy in 
           INTRODUCTORY  ADDRESS.         23
the exertion, and happy in the prospect—governed by the
principles of chemistry, and penetrating by the principles of
mechanics, will  descend  into  the  bosons of nature, will
ransack all the bowels of the globe, will discover new  fer-
tilizing bodies, enabling him to give one common  surface
to the earth, thereby securing an uniformly rapid vegetation,
at once displaying the smiles of a benevolent God,  and the
glories of the animal kingdom.

   TO the art of farming, that  of  cooking is  very nearly
allied.  The object of  this art is to prepare food, and to
render it  most  nourishing  and  palatable ;  which  should
entitle the cook to a respectable rank  among the artists.
The  salting  of  meat,  pickling and preserving vegetables,
baking  bread,  &c. &c. depend on  chemical  principles.
And  on the same is founded the skill  of the dairy maid
in keeping milk sweet and  fresh,  in  making  butter and
cheese,  and preserving them  pure.  Improvements have
not long since been made, by which the rancidity of but-
ter, and tainted meats, can be corrected;  and food can be
so prepared, that one third the quantity commonly consu-
 med,  will support an individual.  Perhaps more important
 discoveries may be made in this branch of  chemistry, when
 prosecuted by persons of strong minds.

   SUCH advantages are greatly exceeded by others,  deri-
 ved from a knowledge of heat.   By a tolerable  acquain-
 tance with  the  laws of  this substance,  the citizens can,
 without  a deprivation  of  comfort, so manage chimneys,
 ovens, furnaces, brick-kilns, distilleries, and all  other re-
 ceptacles  of fire,  as to consume not  half the  fuel ge- 
 24         INTRODUCTORY ADDRESS.
 nerally used.   The  labor  and money  which  this would
 be instrumental in  saving to  mankind,  if properly at-
 tended to,  would  be immense.  The propriety of the fa-
 milies, in the Atlantic states, immediately attending to this,
 is shown by the scarcity and difficulty of procuring wood ;
 which in some parts  is really distressing.   The same intelli-
 gence will also lead to other improvements in common prac-
 tices.  It will enable men,  not only to make excellent sub-
 stitutes for ice, where  it cannot be procured, but  it will
 teach them  of what  materials to construct all  vessels for
 containing ice, so that a quantity of it will last longer than
 double that quantity under common circumstances.   By this
the advantages and luxuries arising from ice, in hot coun-
 tries, will be much more general; as the expences of pre-
 serving it  will be greatly reduced.   Moreover,  this know-
 ledge of heat, might lead to a most material diminution of
 the cost of clothes :  thereby facilitating the arrival of those
 happy times, when the  difficulties of  living will be so les-
 sened, that  all may live  alike ; when an uniformity of ha-
 bits will be established among  men, the absence of which,
 now so frequently  renders common life, and common " li-
 berties but dreary gifts."

   ALL the processes connected with the  metals,  such as
 separating  them from their  ores, purifying, forging, and
 casting them ;  forming particular combinations of them;
 as, brass, pewter, and printer's types ;  converting  iron into
 steel, detecting the presence of such as  are poisonous ;  as,
 arsenic, copper and  lead;  soldering them, &c. depend  on
 chemistry.   The  composition  of  stones,  and   earth,
 form also a branch of this science.  Had these subjects been 
           INTRODUCTORY  ADDRESS.         25
earlier understood, much wealth would have been acquired,
by the earlier discovery of mines and precious stones, which
escaped common observers.   And by the  detection of the
destructive metals,  put in  adulterated wines, and  other
drinks, many persons might  have been longer preserved,
who have fallen victims to such impositions.

   CHEMISTRY, not  only  instructs us in the  means  of
ascertaining the constituents of medicinal springs, but also
in the art of forming waters similar to each.  It teaches the
method of making saltpetre and gunpowder ;  which, during
all wars, is  of  such primary  importance.   This, with the
arts of preparing the various kinds of salts, acids,  and all
the chemical medicines in the shops, which come  under
the head of pharmacy,  might occasionally prove serviceable
to most individuals ; at  least, it would be well to learn the
principles on which they are compounded.

   ANOTHER of the most important objects of chemistry
is,' to  correct the impurity  of  those foul and infectious airs,
which destroy  animals.  Many can readily recal to their
minds the scenes of distress they have witnessed, or heard
of, in consequence of the  impurity of  airs.  But few have
not read of  the deaths occuring from this source, from the
remotest to the  present times.   Accounts of the black hole
of Calcutta, where so many Englishmen suddenly expired,
are fresh in the memory of many;  and no tales are more
common than those concerning the deaths of persons enter-
ing mines,  and rooms, and  caves, in  various parts  of the
country.  This branch  of the science, will not only be  in-
                           D 
26         INTRODUCTORY ADDRESS.
strumental in saving lives, but, by holding out the means of
correcting infected airs,  will  lead  to  the  abolishment of
those vexatious quarantine laws, which serve,  in reality,
only to injure merchants in a shameful degree, without be-
nefiting any part of society.

  THE arts of distilling,  of ascertaining the strength and
purity of  spirits; and of preparing the various fermented
fluids,  such  as vinegar,  wine,  porter, perry, cider,  and
yest,  depend solely on chemical principles.   Some of them
have been highly improved in other countries.  Since the
pernicious practice of using large quantities of such drinks
has become almost universal,  it is of consequence  that the
knowledge of  these improvements be general in this coun-
try.   When this is the case, the considerable sums  of mo-
ney annually expended by individuals for spiritous liquors,
may be  in part saved for the education of their descendants,
as such articles will be prepared at home, for much less mo-
ney.  Already, in  some parts, the  citizens  have  prepared
from the fruit of  the persimmon tree a brandy equal to the
French; and  from pears, a drink  equal to wine,  as I am
credibly informed.

  THE next branch of this science I shall mention is the
purification of filthy waters.   The  importance of this will
be best  stated  by the numerous mariners and persons who
have  suffered from the use of putrid waters.   From late
improvements, it is now completely in the  power of every
one, to  avoid the difficulties arising  from this old source of
pain, disease,  and death. 
           INTRODUCTORY ADDRESS.         27
  CHEMISTRY, also, teaches the arts  of preparing- and
refining all the sugars and oils.   This will prove a source of
considerable emolument, if attended to by large  families,
as they will  be enabled in many instances to prepare their
sugars,  and  also various oils, from common plants.

  THE art  of tanning leather,  which has lately been  so
much improved, the methods of making soap, glue,  starch,
paints,  the varieties  of  inks  and  dyes;  of bleaching,
glazing, and enamelling ; of making glass, -porcelain, bricks,
&c. depend on chemical principles;  and  by them alone
can be explained and rationally improved.

  THE traveller, distressecMbyt."the darkness of nights, and
by the piercing extremes oft cold, will  derive relief  from a
knowledge of  chemistry.  It will direct  him how to revo-
lutionize the scenes around him, to give a  new light and a
new heat with astonishing facility.

   IT is unquestionably true,  that arts have been practised
and some  of them improved,  by persons entirely ignorant
of the principles on  which they depended.   For  example,
leather  has been well tanned,  colors beautifully dyed, and
meats properly preserved, by the most uninformed persons.
Sometimes very important improvements have been made by
artists of this description.   Their discoveries however were
accidental, and for  stumbling on them they deserved no
reward.   Moreover, when they possess a proper  degree of
feeling and  foresight, their operations are slow and painful,
because they are conscious that the termination is doubtful.
Of the uncertainty of their processes,  of their inability to 
28         INTRODUCTORY  ADDRESS.
calculate on results with confidence, the most experienced of
them  will speak.   Now  this state of doubts will be com-
pletely corrected,  if the principles of the art, if chemistry,
be learnt.   Such  knowledge would be to the artists, what
money is to  the commercial  world.   It would give them
strength, confidence, and a firm support. Like money too,
it would  enable the possessor, to  extend considerably  the
sphere of his usefulness.  It might qualify each individual
to make improvements in his art, which would endear him
to mankind till the latest day.  That we have good reason
for indulging in such expectations, appears from the servi-
ces already rendered the arts by a few chemists, who could
do but little more than theorize. Surely, those daily in pur-
suit of a particular branch  of the science, who sensibly ex-
perience the imperfections of its state, are  better fitted for
improving that branch, than the professed chemist, whose
attention is alike claimed by  all  the branches.   Indepen-
dently of this, by studying the art systematically,  or as a
science, although it might not qualify  them immediately
for  expertly practising them,  yet it would enable  them to
learn their trade in one third the time commonly devoted to
it.  Another advantage resulting  from the general study of
chemistry,  amqpg the artists,  would be the increase of li-
berality,  which  would follow the  increase of their judg-
ing and reasoning powers.  That  most of them stand much
in need of  an increase of liberality,  appears from the great
opposition they constantly make to the suggestions and im-
provements of scientific characters, without fairly trying
their value.   We find, frequently, instances of such strong
prejudices continuing for years.   They  seem so well satis-
fied with the state of their  arts, that they ridicule and con- 
           INTRODUCTORY  ADDRESS.         29
demn every effort to improve, as extravagantly erroneous.
Hence we  find,  that tanners refuse  to tan leather in the
same number of days that formerly required weeks:  that
in the construction of houses, no attention is paid to the laws
of heat; and that farmers, in thousands of instances, will not
do as their interests direct.   The time it is hoped will soon
come, when the benevolent  philosophers,  will not have so
frequently to feel for their errors; when condemnation and
contempt will no  more  be withheld from them, for  the
reason,  that " they know not what they are doing."

  OF late years chemistry has been taught publicly in the
schools of Europe.  In France great encouragement is given
to the cultivators of this science.   Its  professors are  sup-
ported, and in some instances have been generously rewarded
by  government.   Under such circumstances,  thousands
annually learn the science without incurring expences.  Since
this has been the case, the most remarkable revolutions have
been wrought  in  their manufactures; abuses have  been
corrected,  processes simplified,  and improvements made,
which the most sanguine supposed scarcely possible.  In
addition to this, new manufactories have been erected,  and
important uses made of articles, which  predecessors had
long neglected.   Worn  out soils have been turned  into
sources yielding wealth and reputation to the industrious ci-
tizensl   Nor did the chemists stop with this success.  They
advanced much  farther ;  they  entered   the  recesses of
nature; they have hailed with pleasure the contents »f the
tomb, converting the putrid carcases  into masses highly
useful to living animals! 
30        INrRODUCTORY ADDRESS.
   THE love of chemical pursuits has not been confined  to
men.   That sex whose virtues reflect so much honor  on
the human race, caught the taste for this interesting study,
particularly in France,  the ladies enthusiastically espoused
the cause of chemistry.  The fate  of  the beloved lady
Chevraud, who fell a victim to an experiment she instituted
to aid the warriors of her country, will long excite a gene-
rous condolence.   The zeal displayed  by  other  females
in this polished nation, has  a strong claim for  admira-
tion.   Their  glorious  occupations  cannot  be too  fre-
quently held up for imitation.   They deserve to be followed
by " the  fair ornaments of  the western world."  May the
bright examples of the daughters of America grow brighter
still! may their success establish their rank in the  intellec-
tual world, while it creates blushes of shame and weakness
on the cheeks of those men failing to walk in their ways !

   THE  time  is now come, when the citizens of America
should act  entirely for themselves;  when they  should for-
ever cease  to depend on the  caprice of  foreigners, for the
innumerable chemical compounds.  This fair portion of the
civilized  world, to have its beauties enjoyed, and its excel-
lencies duly appreciated, must in all its parts be adorned by
native  chemists.  The  dignity of independence  and  the
glory of  usefulness,  should rouse the love of science from
the lethargic  dispositions in  America.   Animated by  the
noble emotions, her  citizens would rally around the temple
of  fame, would become raised to the rank  of  a Newton,
an interpreter of  nature, and astonish  the  old  world, as
much  by the sacred flashes of genius  as by the purity of
their political creed.  The lights of science would then give 
           INTRODUCTORY  ADDRESS.         31
a lustre constituting  a new era in the annals of the crea-
tion.  The same objects, truth and usefulness, would prove
a connecting bond between  every individual;  and but a
short time would then elapse,  before it became the universal
cry, that the road to science was the road to happiness.

  NO individual can now do too much in promoting the
study of chemistry.   The call for immediate advancement
throughout the republic is great.   Ye free agents! ye guar-
dians of the young! can you allow those under your care to
neglect learning the principles of this all- important science ?
What then will you say, when  arraigned at the bar of justice,
before a Creator and an assembled universe, for neglect of
duty! Your hoary locks will not cover you!  the number of
the accused will  naught  extenuate—and in vain will you
deny the  charge!  The children  of successive  generations
will rise up around you!  In the face of heaven they will bit-
terly complain of the beauties to which  they were insensible!
while humanity,  bewailing her  misfortunes, will recount
the number of  blows  she received, and  the number of  de-
nials made to her call,  because  these creatures could not
perceive the pleasures of her paths !

  BUT, fellow-citizens, I really feel incapable of properly
stating the  beauty,  the connexion,   and the  importance
of the science  of chemistry.   For you to know these
you must  know  the science  itself.   This  understood,
your souls  would  feast on the eternal beauties of nature,
while you were inhaling the grateful incense  arising from
your seryices to the cause of humanity. 
52         INTRODUCTORY ADDRESS.
  WARMLY wishing my countrymen the greatest suc-
cess in their scientific researches, I shall now proceed to the
detail of those principles and improvements which have been
made by chemical philosophers—-----

     —————— " And truth shall be our guide,
      Our golden theme, our glory to the last."
$1/%$ 
CONTENTS.
              INTRODUCTORY ADDRESS, Page 17.

  Containing an ennumeration of the connexions and importance of the science
                           of chemistry.

                     DISCOURSE I, Page 41.

  Containing general remarks, and a particular account of heat. To wit; defi-
 nition   of chemistry, properties of bodies, gravity; specific gravity dis-
 tinguishes bodies  form each other,  mean? of ascertaining it.  AUracti.mof
 cohesion, causing the form of  bodies; crystallization; acts only between
 bodies  of the  same kind.  Affinity, o.  chemical  attraction;  operates
between  bodies of different kinds, cbau cs  their proieitus  and varies
with the state  in which bodies are  placed, giies rise to many phenomena,
&c.  Page 45.  Chemists discover that the bodies around us may be convert-
ed to certain states from which they cannot be further changed, in vhich
they are called ELEMENTS, which  variously  combine and form  COM-
POUNDS,  which are named according to the names  of the constituents,
page 50.  The first element claiming attention, is called heat, or caloric ;
definition, it  pervades all nature, it creates  circumstances  for changes
to take place in bodies, as dilation or rarefaction ; cooking ; distillation ; a
still, page 54.  Heat measured by instruments; thermometers, Fahren-
heit's,  Reanmer's, and Wedgewood's.  It p;it.ses  through  bodies, moie or
less, quickly,  and they are called good or bad conductors:  metals good
conductors,  airs,  coal, &c. the  reverse ;  their  use in  preserving ice ; re-
marks concerning the receptacles of ice ;  uses of the skins and clothes of
animals.  Heat unites to bodies and is called latent heat; produced by che- 
34
CONTENTS.
mical changes, when absorbed, coldness is produced;  means of producing
great coldness by nature and art, page, 65.   Means of  exciting heat,  most
produced by Mr. Hare; theory of combustion, burning of volcanoes, de-
tonation ;  production of rain, hail, and  snow;  heat of steam,  used  for
cooking, machine  for the  purpose, page 73.  Opinion of Dr. Black  con- ■
r* ruing heat, erroneous; proofs of the materiality of heat, page 75.

                      DISCOURSE II, Page 78.

  Concerning Light, Electricity, and Galvanism, To wit; definition of light
and some of the terms relating to it; refracted by some bodies; reflected by
others, whose reflecting surfaces enable it to excite in us the ideas of color;
vegetables bleached or whitened when light is prevented from acting on them;
combines with bodies like heat; is extricated during chemical changes ; solar
phosphori;  its  influence on animals, vegetables, and other bodies, page 88.
Electric fluid, called lightning ; resembles heat and light in some particulars,
combines with bodies, is extricated during chemical changes in the clouds,
&c.  is  collected by an apparatus for experimenting, is carried off by me-
tallic conductors; in its passage through air extricates the latent light of the
air so as to cause a flash, page 91.   Galvanism, page  92,  resembles  elec-
tricity, collected by the chemical action of  oxigen on metals,  page 93.

                      DISCOURSE  III, Page 94.

  Concerning the Atmosphere and  Water.   To wit; definition of aeriform
bodies; examined by means of an apparatus; atmospheric  air  separated
into two other  airs, called oxigen,  and nitrogen air; properties  of oxigen
air,  it  unites to bodies forming or ids,  and also acids; their  properties j
means of  collecting oxigen air; nitrogen air, its properties, method of ob-
taining it  pure.  When united in certain proportions, they  form our atmos-
pheric  air; this air is frequently impure, the quantity of oxigen it contains
ascertained  by an eudiometer; contains fixed air and  kills animals; con-
tains infection; means of correcting or  destroying it,  page 105.   Oxi«-en
and nitrogen unite in different proportions, forming different compounds
page 104.  They form the nitric acid, its properties ; they form the nitrous
acid, its properties ;  they form nitrous air,  its properties; and also nitrous
oxid, its properties.  Water,  page 116, ice;  water;  steam; water dissolves
or  chemically unites to bodies, is a most important agent, its boiling  in-
fluenced by pressure of the  air,  fited from fetid impurities by  means of
charcoal,  also by  distillation, is found to be a compound formed  of oxigen
and an element called bidrogen;  hidrogen air, its properties,  means of
preparing it.

                      DISCOURSE IV, Page 121.

   Concerning Carbon, Sulphur, Phosphorus,  and the Muriatic,  Borack, and
Fluoric Acids. To wit; carbon, pure in the diamond -} unites to oxigen forming 
CONTENTS.
35
  darbonic acid, and td iron forming steel,  properties of pure carbon or dia-
  monds; they are in a  strong heat in the presence of oxigen,  converted
  into charcoal and carbonic acid.   Plumbago contains much carbon,  also
  common pit or stone coal, and charcoal or the remains of burnt vegetables,
  properties and uses of charcoal, it is a solid oxid of caibon ;  aerial oxid of
  carbon obtained from it, which is  very inflammable;  carbon unites in one
  portion tohidrogen air forming light carbonated hidrogen air, and in a larger
  portion forming heavy carbonated  hidrogen air.   When fully combined with
  oxigen it forms carbonic acid, or  fixed air;  properties of this air,  it exists
  in great abundance in  nature,  water impregnated with it  by  means  of
  Nooth's apparatus, united to other bodies it forms carbonates.   Sulphur,
  page 131,  how obtained,  its properties, unites to oxigen in different quan-
  tities forming the sulphureous acid, properties of this acid, with  a  larger
  quantity of oxigen it forms the sulphuric acid, properties of this acid, elixir
  vitriol; united to other bodies it forms sulphates ; sulphur unites to hidrogen
  forming sulphurated hidrogen  air,  its properties; sulphur unites also  to the
  metals  forming sulphurets,  page 135.   Phosphorus, how  obtained,  its
 properties, it unites to oxigen forming  the phosphorous acid, its properties,
  in a larger quantity it forms the phosphoric  acid, its properties; united  to
 Other bodies it forms phosphates, it unites to hidrogen air forming  the phos-
 phorated hidrogen air,  its properties ;  it unites to the metals forming phos-
 phurets.  The muriatic acid,  page 140, exists pure only in the form of air,
 how obtained,  its properties;  united to other bodies it forms  muriates;   it
 unites  to oxigen  forming the oxi-muriatic acid, its  properties; used for
 bleaching bodies and purifying airs.  Fluoric acid, how obtained,  its pro-
 perties; dissolves glass,  united to other bodies it forms.fixates, &c.  Boracic
 acid, how obtained, its properti es; united  to other bodies it forms borates.

                      DISCOURSE V, Page 145.

   Concerning the Alkalies ; Ammonia ; Potash and Soda.  To wit; general pro-
perties of alkalies; united to acids they form compounds called neutral salts.
Of ammonia or the volatile alkali,  its properties, haw obtained ; carbonate
of ammonia or conerete volatile alkali,  its properties and uses; muriate of
ammonia or sal-ammoniac, its properties and uses.  Potash or the vegetable
alkali, how obtained, its properties and uses, it unites to sulphur forming
sulphuret of potash.   Carbonate of potash or mild vegetable alkali, its pro-
perties and uses ;  sulphate of potash or vitriolated tartar, page  152.   Com-
mon nitre,  saltpetre, or nitrate of  potash,  how obtained,  its uses.   Gun-
powder,  how made; fulminating powder, how exploded, page 155.  Soda
or the mineral alkali, how  obtained, its properties and uses; carbonate of
soda or mild mineral  alkali, its properties and  uses ; common   salt or
muriate of soda, its properties, methods of obtaining it from sea water •
nitrate of soda or cubic nitre, page  160.   Glauber's salts or sulphate of soda'
how obtained, its properties and uses,   Phosphate of soda,  how prepared 
3&                          CONTENTS.

its uses.   Borax or borate of soda,  where obtained, its uses.  Concerning
soap page 162.  Soap of ammonia or volatile liname.it,  how made ;  soap of
soda  orchard  soap, how mnde, how adulterated; soap  of  putash  or soft
soap, how made; soap of wool,  how made; general properties of soap,
soap of lime.
                      DISCOURSE VI, Page 169.

   Concerning the Elementary Earths. To nit ;  properties of earths in gene-
ral;  all the earths including  stones, reduced to 9  different  states  from
which  they  cannot be varied.  First earth called silex, very  abundant,
 forming rocks, &c. obtained pure,  its properties used to form  glass,  me-
 thod of making various kinds of gla>«, page 172.  Second earth, aluinine,
 very abundant, forming the chief part of soils, of clay,  &c. how obtained
 pure, its  properties, unites to acids forming  neutral salts,  with the sul-
 phuric acid, it forms alum, properties of  this salt,  how  obtained  for the
 purposes  of  commerce,  page 175, alumine  used  for making stoneware,
 method of making pottery, queen's ware, china, and bricks, page  177. Third
 earth, lime, \eiy abundant, how obtained pure, its properties, soluble in
 water,  how  to  make lime water, unites to acids,  with  carbonic  acid
 it forms  chalk,  marble, limestone,  calcareous spar,  &c. their  properties,
 with sulphuric acid,  lime forms plaster of Paris or sulphate  of iime, pro-
 perties of this compound, its uses;  nitrate of lime, muriate of lime, fluor
  spar or  fluate of lime,  phosphate of lime, mortar made of  lime,  me-
  thod of  making mortar,  impro\ed highly by burnt  bones,  page  179.
  Fourth earth, magnesia, where found,  how obtained pure, its properties;
  unites to acids,  with carbonic acid it forms the uncalcined magnesia of the
  shops, or carbonate of magnesia, properties of this compound ; with sul-
  phuric acid this earth forms Epsom salt, or sulphate of magnesia, its pro-
  perties;  muriate of magnesia, &c. page 187.   Fifth earth, barytes,  where
  found, how obtained, its properties.  Sixth earth, strontites, how obtained,
  its properties.  Seventh earth,  zircone, its properties.   Eighth earth, glu-
  eine, its properties.   Ninth earth,  yttria, its properties.

                       DISCOURSE VII, Page 193.

      Concerning the metallic bodies.  To wit;  general properties of metals,
   twenty  two different kinds noticed—1 Mercury, where found, how obtained
   from its ores, its properties—when oxided, unites to the acids, red precipi-
   tate or  nitrate of mercury, corrosive sublimate, or oxi-muriate of mercury
   how prepared,  its propeitits;  converted into calomel,  or muriate of mer-
    cury; properties of calomel.  2  Platina,  where obtained,  the heaviest
    metal,  its properties.   3 Gold, where  found, how purified,  its properties •
    the arts  of gilding.  4 Silver, where found,  how purified, its properties •
    oxided, It unites to the nitric acid, forming nitrate of silver, or caustic, its
    properties; muriate of silver; art of silvering and plating,  page  209*.— 
CONTENTS.
3?
5 Copper, where found,  how  purified, its properties; nitrate of copper,
blue verditer;  sulphate of copper, or blue vitriol,  its properties;  verdigris,
or acetate of copper, its  properties ; arseniate of copper : its alloys ;  tom-
bac, brass,  bell metal,  &c.  6 Iron, page  218, where  found,  how  sepa-
rated, its properties;  steel,  how made,  a new method, its pioperties,
converted into iron ; copperas, or sulphate of iron, its properties and uses:
muriate  of  iron, flowers  of steel, chalybeate  waters;   Prussian  blue,  or
Prussiateof iron, how made ; the prussic acid,  its properties, &c.


                     DISCOURSE VIII,  Page 229.

   Metals continued.  To wit; 7 Tin, where found, how obtained, its proper-
ties; making looking glasses,  tinning iron and copper  vessels;  oxids  of
tin used for paints, united to acids, composition for dyeing scarlet, page 235.
8 Lead, where  found,  how  procured, its  properties; it unites  to oxigen
forming  litharge, massicot, &c.  its oxids  unite to acids, sugar of lead  or
acetate of lead, muriate of lead, or patent London yellow,  sulphate of lead
alloys of lead.   9 Zinc,  page 240, where found, how procured, its proper-
ties, nitrate of zinc, white vitriol or sulphate of zinc, its properties and uses.
10 Bismuth, where found, how obtained, its properties and uses.   11  Anti-
mony,  where found, how obtained, its properties and uses;  glass of anti-
mony,  antimonial wine,  tartar emetic,  butter of antimony, James' pow-
der, Kermes' mineral   12 Arsenic,  where  found, how obtained, its pro-
perties  and uses.   14 Cobalt,  where found, how obtained, its properties;
forms a sympathetic ink, used  to make zaft'er smalt,  method  of making
 them.   15  Nickel, page 258,  where obtained,  its  properties when  pure.
 16  Molybdena, where  obtained, its properties.   17  Tungsten,  where
obtained,  its properties.  18  Uranium,  where obtained-,  its properties.
19 Titanium, where obtained,  its properties.   20 Tellurium, where ob-
tained,   its  pioperties.    21  Chrome,   where obtained,  its properties.
22 Columbium, where obtained,  its  properties.  Recapitulation,  but 46
simple or elementary substances found.

                     DISCOURSE  IX,  Page  272.

   Concerning some of the productions of the Mineral Kingdom. To wit;  water
of the sea,  its  constituents.  Mineral waters, page 275, their constituents,
art of decomposing them, &c.  minerals divided  into  4 classes.  Stones divi-
ded into 9 heads,  bearing the names  of .elementary  earths.   Salts, not nu-
merous.  Combustibles,  several kinds, sulphur, diamond, bitumen,  page
285, naptha,   petroleum, mineral tar,   pitch,  maltha,  asphalt,  elastic
 bitumen, pit  coal, several kinds; jet, canal coal,  common coal, amber,
 plumbago,  their properties, ice.   Metallic ores,  arranged under twenty-two
 heads,  &c. 
58
CONTENTS.
                      DISCOURSE X, Page 293.

  Concerning Vegetable Substances. To wit; general remarks concerning ve-
getables, their  composition, reduced to sixteen different states, in  which
they are called proximate principles.   1 Wood, or ligneous fibre, its pro-
perties, means  of preserving it.  2 Acids, seven kinds, citric acid, or acid
of lemons, malic acid, or acid of appLs, gallic acid, or acid of galls, ben-
zoic acid or acid of benzoin,  tartareous acid  and acetic acid or acid of
vinegar; means of preparing these acids, their properties;  of making good
ink, cream of tartar, of the process for forming vinegar or acetous fermen-
tation ;  of the  acids of cork,  amber and camphor.  3. Tannin, page 305,
how obtained,  its  properties;  used  to  tan  leather.  4  Oils,  two kinds;
expressed oils,  oil of  olives,  linseed oil, castor oit;  method of obtaining
them,  &c.   Essential oils, how obtained, their properties.  5 Gluten, how
obtained,  its properties.   6  Fecula or starch,  how obtained,  its  pro-
perties ; method of  making  bread.  7 Indigo, how obtained,  its  pro-
perties, &c.

                     DISCOURSE XI,  Page 322.

   Vegetable Substances continued.  8 Sugar,  how obtained, its  properties j
syrup, ferments and is changed to alcohol or ardent spirit, wine, porter or
beer, cider, &c.  Of  ardent  spirit, or alcohol obtained by distillation, its
properties,  means of ascertaining its purity,  unites to acids forming ether;
preparation of sulphuric, nitric, acetic and phosphoric  ethers, how they
are made, their uses, &c.  9.  Gum or mucilage, its properties.  10 Resin,
their properties; form varnishes when dissolved,  art of making the differ-
ent varnishes;  of  balsams, page 340.  11 Extract,  its properties.  12 Elas-
tic gum or Indian  rubber,  its  properties.   13 Camphor, its properties.
14 Wax, its properties;  how  bleached.  15 Bitter principle, its properties.
16 Narcotic principle,  its properties.   Putrefaction of vegetables, page 347.
Recapitulation.

                     DISCOURSE XII, Page 351.

   Concerning the growth  of vegetable bodies. To wit; plants grow from seeds,
which combine with their food contained in the earth, which  is converted
into sap that circulates through them ; theory to explain these phenomena:
of the laws of  plants; their functions, &c.  360.  Of the  food of plants;
ef soils; of manures; their manner of operating, the best kinds, &c.

                     DISCOURSE XIII, Page 372.

   Concerning  animal parts. To  wit;  of  substances  which are found in
 abundance  in  animals.  Of gelatine,  its properties; of glue, of size of
 isinglass, their uses, &c.  Of albumen or white of eggs, of fibrina or the 
CONTENTS.
59
 coagulating part of blood;  of oils, spermaceti, fat, train oil, animal oil of
 Dippel, their properties, uses,  means of purifying them, &c.   Of amber-
 gris, page 384, of castor, of civet, of sugar of milk and of urine; of can-
 tharides or Spanish flies, cochineal,  gum lac,  &c.  Of  animal acids, the
 Prussic acid, lactic acid or  acid of  milk,  sebacic acid or acid of fat, uric
 acid or acid of urine,  amniotic acid.  Of the hard parts of animals, p. 390;
 of bones;  of horns,  nails,  scales, muscles or flesh; means of preserving
 it from putrefaction; of skins,  membranes, tendons, ligaments, glands,
 brain, nerves, hair,  feathers and silk;  method of bleaching silk.

                    DISCOURSE XIV, Page 404.

   Concerning theflx.idsof animals. To wit;  of  blood,  its separation  into a
 clot, and a  fluid called serum, used in clarifying liquids,  &c.  Of milk,
 its quantity,  how increased,  its cream;  of  butter,  how increased  in
 quantity and purity, means of preserving it from  rancidity ; of whey, its
 properties and uses; cheese,  the method of making the best j of the milk
 of women, asses, goats and ewes; mares' milk; of bile, its qualities, com-
 position, uses,  &c. page 420.   Of the gastric juice,  or secretion of the
 stomach,  its qualities, coagulates milk,  useful to  mix with medicine, &c.
 Of urine, page  425,  its qualities, composition, state in  disease, &c.  Of
 poisonous secretions; of saliva.

                     DISCOURSE  XV,  Page 433.

   Of substances  which nourish animals;  of  the  conversion of food into
 ,chyle, chyle into venous blood, venous blood  into arterial, arterial  blood
 into secretions,  &c. principles on which these changes depend; putrefac-
 tion of animal bodies.  Of coloring bodi s, page 445;  principles on which
the art depends; division; bleaching; dyeing;  articles necessary; dyein*
Tyrian purple and scarlet.

               CONCLUDING ADDRESS, Page 453.

  Recapitulation of principles; what  may be expected from the prosecution
 of the science.
DEFINITION OF CHEMICAL TERMS, Page 465. 
TO  THE READER!
  Several very material typographical errors have most un-
fortunately escaped an earlier detection,  in consequence of
parts  of the work being  unusually  hurried  through  the
press.   Such as do not change  the sense are not of conse-
quence, but  the reader is particularly requested with his
pen to correct the following :

     Page. Line from  the top.
      51   12th, for unexceptionable, exceptionable.
     Ii3   18th, for Barneo, Borneo.
     171   11th, for grantie, granite.
     183   last line,- erase on.
     195   12th, for allays, read alloys.
     do    15th,  for  do.        do.
    216    8th, tor states, strata.
    222   26th, for carburet, carburet.
    226   21st, iox disposition,  deposition.
    236   11th, for molydate, molybdate.
    241    1st, for confined, combined.
    246   15th, for a nitrous, an.
    250   14th, for antimony, arsenic.
    268   ^d, for  red, white.
    270    1st, \ox phosphorus, phosphorous.
    302   14—15th,  for of being,  of not being.
    308   10th,  i^rtar, tann.
    392   10th, for  Gibraltar do, Gibraltar they do.
    396   last line, for is much exercised, are much increased. 
DISCOURSE  I
     IJEFORE treating  of particular  substances, it will
be proper to offer some general observations, with which
beginners should make themselves acquainted,  although
they may appear uninteresting.              ^

  THE object of chemistry being, to ascertain the proper-
ties or qualities, or laws of  matter; it follows, that every
thing around us, commencing with  the air, and ending
with the earth, are the subjects of chemical research.   A
correct knowledge of their laws or properties, can only  be
acquired, by noticing the changes produced in  the bodies,
in the  various  circumstances in which  they  are  pla-
ced.   In order to notice  these, one  substance is applied
to another, in the state which experience has shewn to  be
proper for  changes to be produced.  This application  of
one  body to others,  is called an  experiment, operation,  or
chemical process.  " Chemistry, therefore,  consists," says
                           F 
VI
DISCOURSE  I.
 the perspicuous writer, Mr. Accum, "in a detail of those
 facts, which are founded on experiments and observations.
 Its basis is experience; from this,  by regular  conclusions,
 it deduces principles  or theories ;  and connects a series of
 established facts into a certain  order, called a system."

   IF we elevate  a body from the earth, on taking away the
 support, it immediately falls down.  This  return to the
 earth, is an effect produced by a  cause, which,  although
 not known, is designated by the term attraction of gravity.
 It  is, therefore, by the attraction of gravity, or a law of
 matter,  that bodies  tend  towards  the earth;  and  on the
 same depends their adherence to it.   We find, that one body
 adheres much more strongly to the ground than another;  or
 in other words,  has more  weight  or  gravity.   This is  in
 consequence of  the attraction  of one to the earth, being
 much stronger than that of the other.  For example, it is
 more difficult to raise a lump of lead of a given bulk than
 an equal bulk of cork; because the  lead is more powerfully
 attracted by  the earth than the cork, on which the  weight
 or gravity depends.   It is in consequence of  this attraction
 of gravity, that  the rain  and snow descend—and that all
 fluids move until their surfaces  are even; whereby the great
 falls of  water, currents of  rivers, runs, &c. are occasioned.

  AS bodies of  equal bulk are found to differ so materially
 in their weight,  advantage is taken  of it, for the purpose
 of distinguishing them from - each   other.   The weight  of
pure  water is  considered  as a standard by which  that of
 other bodies is determined.  The weight of a given bulk
of this, say  one pint, being ascertained, then the weight
 of an equal bulk of other bodies is  to be found out, which
when done, the  weight  of the water is to be  deducted
from it, and the difference is called the specific gravity of the
 hdy.  Commonly the weight of water is expressed  by the 
DISCOURSE I.
43
number 1,000, and that of other bodies in proportionate
numbers.   The  specific gravity  of bodies heavier than
water, is best ascertained by weighing them in it.  By this
it will be found that the heaviest body known,  platina,  has
a  specific  gravity,  20  times greater  than  water;  that
the specific gravity of lead is about  11  times greater ; and
so a great  variation in  the  specific  gravity of most bodies
will be noticed.  The body whose specific gravity is least,
appears to  be an inflammable air, which is 13 times lighter
than atmospheric air;  which last is  910 times lighter than
water.

   AFTER noticing  the adherence of bodies to the earth,
and attending to the cause called attraction of gravity, which
was found to operate  with various  degrees of force,  we
next observe the forms and consistencies of the substances
around us—varying from the extreme hardness  of a stone,
to the softness of jelly; and from the fluidity  of water
to that of airs.  These  different forms and consistencies,
proceed from a cause, which is  designated by the term,
attraction of cohesion or aggregation.

   CONCERNING this attraction of cohesion  the follow-
ing is known:  it exists very strong between two particles of
matter of the same kind.  Hence, if you bring two drops of
water near each other, they unite and form one drop.   It
is to this cause, that small quantities of fluids have a globu-
lar appearance, as rain, when no opposing force  prevents.
In other cases, this attraction of cohesion, causes the par-
ticles  of a  body to assume a  particular regular shape, of
several sides,   as  saltpetre,  or common  salt,  or  stones.
This is  termed crystallization,  as  the bodies so formed are
sometimes  like crystals.   It should be recollected, that  the
exercise of the attraction of cohesion never alters the nature
or qualities of substances; it only serves to give them shape, 
U                 DISCOURSE I.
to preserve  and increase their bulk.   The  force  of this
power, or the degree of cohesion, is diminished by increas-
ing the distances between the particles of matter; and by
this separation the cohesion may be  entirely destroyed.—
Hence when it is designed to lessen it in a  hard body, so
that it may be fluid, or destroy it so that it may be powder,
then a mechanical force,  stronger than the attraction, must
be applied.  For this purpose, heat or fire, which  enlarges
bodies, is applied in many cases.   Metals, wax, tallow, &c.
when heated so as to melt, have their  fluidity,  in conse-
quence  of this, that  their particles are  separated by  the
heat,  so as to lessen their cohesion;  and, in consequence of
the same  diminution of  cohesion,  mercury, water,  and
other substances, are converted into steams or airs,  when
the  heat  is still  more  increased.   In  the  first instance,
bodies are said to be melted or fused;  such are called  fu-
sible bodies, and those we cannot melt are termed infusible.
Whn it is intended to powder hard substances, or in other
words,  to divide them into their integrant parts,  then other
mechanical forces are  used; such  as grinding, cutting,
filing, rasping, pounding, breaking, &c.

   ON  extending our  general  examination of bodies, we
 find, that some have a remarkable tendency to  unite with
 others of a dissimilar kind, by which a most material alter-
 ation in the properties of the substances is effected.   Thus
 we find,  that  iron will unite to air,  and become rust, so
 as to lose its metalic properties: that  an acid,  as vinegar,
 will unite to the alkali, called potash, and form a compound
 unlike  either of the  ingredients: that sulphuric  acid unites
 to lime,  and forms plaster of Paris,  a compound possessed
 of none  of the properties of its constituent parts: that fat,
 or oil, unites to an alkali,  and forms soap,  a substance
 possessed of  new  properties,  and  so  forth.     All  such
  changes  arise from a  cause—another kind of attraction, 
DISCOURSE  I.                  45
 called affinity, attraction of composition, or chemical attrac-
 tion.  This  must appear very different from the attraction
 of cohesion; for, the exercise of the attraction of cohesion
 does not alter the nature or qualities of bodies, and this in-
 variably does.  When the affinity between any two substan-
 ces is exercised, the body formed  is called  a compound,  or
 chemical mixture ;  and, the substances forming it are term-
 ed its component or constituent parts, to distinguish them
 from the integrant parts of a body; by which is only meant,
 a portion of a mass.    Two  substances may be  intimately
 mixed with each other :  but, however intimate this  mixture
 be, it still consists of dissimilar parts,  which may be sepa-
 rated from each other by mechanical means.   We may mix
 mud  with water, and they may be separated by mechanical
 means; b at  if salt be added, then the salt and water chemi-
 cally combine, and can only be separated by  chemical affini-
ties.  The smallest integrant part of the compound will be
 found composed of a part of each ingredient, or constituent
 part.  The only way to  disunite or decompose  them, is by
 the action of a stronger affinity than that uniting them to-
 gether.   Before the exercise of the affinities of bodies are
 changed,  it is  necessary that the attraction of cohesion
 should be destroyed.   Hence heat, light, electricity,  galvan-
ism, and  any thing which lessens  the cohesion of  bodies,
 are found to favor the exercise of the affinities of substances
 for each other.

   BEFORE an affinity can  be exercised,  it is  necessary
that the state or circumstances for its exercise should previ-
ously exist.   We know,  for example, that the attraction of
gravity does  not operate  on a body we elevate, so as to bring
it to the ground,  unless the cause of  the elevation be re-
 moved ; when done,  the circumstances for the exercise of
the attraction exist, and,  consequently, the body falls to thq 
46
DISCOURSE  I.
 ground.  Just so with the affinities of bodies ;  the state for
 their action must be created before they can be exercised.

   THE attraction of gravity produces always one uniform
 effect;  and that is,  bringing bodies to the  ground.   But
 not so with the  affinities  of substances.   The affinities of a
 substance,  are found to vary very  much with the circumstances
 in which the substance is placed;  although they are always the
 same in the same circumstances.    For  example;  two sub-
 stances, called nitrogen and oxigen,  will, by means of  a
 large quantity of electricity, unite together and form a fluid :
 the same  fluid (the nitric  acid) in a high degree of heat, is
 converted into airs; again,  iron, in one state,  will remain
 pure ;  in  another  it  will unite to air, and become rust; in
one  state  it  will be solid, and  in  another  fluid; and the
 same may be said  of most substances in nature.

   THE circumstances, or condition or state, in which the
affinities of bodies are exercised, vary prodigiously.   All
of them, no doubt, depend on a certain mechanism,  or ar-
rangement of matter,  which cannot be described.  We
know, that heat,  light, electricity, galvanism, and  some-
times, other  fine substances, are instrumental in creating
the state or circumstances in which the affinities of a body
are variously  exercised.   Such is the nature of these states,
that we can only form an idea  of  their existence, by the
 formation of  a compound, or exercise of those affinities of
 a body peculiar to  the state; nor are we able  to say in what
one state differeth from another.  All we can do is, to give
 the fact.  Chemists should be particular, however, in men-
 tioning what appears to create the  state, when they notice
 the exercise of the affinities  of  substances.   For example,
 they should mention, whether it was light, or heat, or elec-
 tricity,  and so forth, which seemed chiefly instrumental. 
DISCOURSE  I.
47
  BY the exercise of the affinities of substances, chemists
have ascertained,  that the bodies around  us, compounded,
or formed by the  chemical union of  other bodies, are very
numerous.  They have ascertained  this by two methods j
the  first is  called decomposition, or analysis, by which  is
meant, not the division of a substance into integrant parts,
but the eeparation or disunion of its constituent parts from
each other: the second  is called re-combinatiott, or synthesis,
by which is  meant the union of the constituent parts of a
body together,  so as to form the same  substance they did
previous  to decomposition.   In  order  to re-combine  or
form again a body, it is only necessary, to add together the
substances into  which it was decomposed.   But,  to decom-
pose a substance,  it must be  subjected to the exercise of  an
affinity,  stronger  than  that which caused its combination.
For example, if to the compound called  chalk, (which is
composed of lime  and carbonic  acid) you add sulphuric
acid, a decomposition takes place.  By virtue of a superior
affinity the sulphuric acid unites to the  lime, and the car-
bonic acid is disengaged  in the form of air; which, while
escaping, causes that  motion  called effervescence.    But,
when we add together  two compounds, as Glauber's salt,
which is composed of sulphuric acid and soda;  and the ni-
trate  of lime,  which  is composed of the nitric acid and
lime, then the  affinities of each of the substances are ex-
ercised.   The  sulphuric acid unites  to the  lime, forming
plaster of Paris, or sulphate  of lime,  while the nitric acid
unites to the soda, forming  the nitrate of soda-   Decom-
position so effected, is said to be by compound attraction.—
Tables,  shewing  the relative attractive  powers  of bo-
dies, have been formed,  and are  of great  service  in re-
freshing the  memory.   When decomposition  is effected
through the agency of water, it is said to be done in the humid
way; when without the  water, in the dry way.  When a
solid body is added to a fluid,  for which it has an  affinity 
48
DISCOURSE  I.
(or tendency to unite) the two unite together and form  a
substance—not like a mixture, in which one body is merely
suspended in another, but a chemical compound;  for, very
frequently, the bulk of the fluid  is not increased by  such
combinations.  In this  case, the solid body is said to  be
in a state of  solution or dissolved in the fluid,  and when no
more of the solid can be  dissolved, it  is called a saturated
solution.  If to this solution, you add a substance for which
the fluid has a stronger affinity than it has for the one it con-
tains, then they unite together, and the first  falls  to the
bottom.   In this case,  the substance falling down,  is said
to be precipitated; and that which caused it is called the pre-
cipitant.  For example,  if to a saturated solution of salt-
petre in water,  you add  pure spirit,  for which the water
has a stronger affinity than it has for the saltpetre, then they
unite together, and  the saltpetre falls to the bottom,  or is
precipitated; and the spirit is called the precipitant.  When
a solid is disengaged, and rises up in vessels, it is said  to be
sublimed.  But, if it be a fluid, it is said to be evaporated, or
volatilized,  which if condensed in vessels, is said to be
distilled.

   CHEMISTS  have reduced all the variety of compounds
around us  into  a  few bodies, which they cannot  further
reduce.  These, which they  cannot  further decompose,
are called simple or elementary bodies;  and  of course all
the bodies around us are compounded of these few simple
substances or elements.  Formerly chemists  guessed that
every thing was composed of five or six elements;  but, by
the modern method of reasoning from facts which are ascer-
tained, it appears that there are about forty-five  simple or
elementary substances,  which  they cannot further decom-
pose  Of these, are heat, light, electricity, galvanism,  car-
bon, phosphorus, sulphur, iron, silver, gold,  copper, &c.
 &c. &c.  It is probable that several of the substances, now 
DISCOURSE  I.
49
considered as elementary,  may hereafter be shown to be
compounded; but this is only common conjecture, which
should not be credited till established by experiments.

  To give correct names to the elementary and compound-
ed bodies has occupied  much of the time of modern  che-
mists.  It was proposed to  name  the  simple substances,
from some striking  quality which  they possessed, unless it
be forbidden by  constant custom.  For  example, there  is an
air remarkable for forming nitre or saltpetre ; this is there-
fore to be called nitrogen air.   Substances compounded of
others it  was proposed to name after their component parts.
For example, Glauber's salts are composed of sulphuric  acid
and soda, and are therefore called sulphate of soda.  By this
it was expected to avoid the various and whimsical deno-
mination of  substances  by different persons,  and  also to
favor the memory in recollecting the constituents of  a body
when it was called.   On this is founded the new nomencla-
ture,  which has made so much  noise in the world  of late
years; and which is,  beyond all doubt, of  great value, if
not abused by the alterations  of too many innovating  and
obtruding hands.  Every one should  learn something con-
cerning it.  The great French chemist, Mr. Lavoisier, speak-
ing of this,  observes, that «the impossibility of- separating
the nomenclature of a science  from the science  itself, is
owing to this,  that every branch of  physical science must
consist of three things;  the  series  of facts which  are the
objects of science; the ideas representing  these facts,  and
the words by which these ideas  are expressed.  Like three
impressions of the same seal, the  word ought to produce
the idea, and the idea to be a  picture  of the fact.   Now,
as ideas are preserved  and  communicated by  means of
words, it necessarily follows, that  we  cannot  improve the
language of any science,  without at the same  time im-
                           G 
50                 DISCOURSE I.
proving the science  itself;  neither can we, on the other
hand, improve a science,  without improving the language,
or nomenclature, which belongs to it.  However certain the
facts of any science,  and  however just  the ideas we may
have formed of these facts, we can only  communicate
false or imperfect impressions of these ideas to others,
while we  want words by which they  may be  properly-
expressed."
  BESIDES the general laws of matter, the attractions of
gravity and  cohesion, and chemical affinity, philosophers-
have considered another, called repulsion, by which different
bodies are kept apart.   The cause of the separation of such
bodies is a  mechanical one,  as  in   most  cases  will
appear evident; and consequently, it would be improper to
conclude there was a repulsive principle.

  Having premised these general observations, I proceed
to consider  the particular substances around us, and  first
of the four,  named heat,  light,  electricity  and galvanism^.
which are termed unconfinable elementary, bodies.
CONCERNING HEAT.
  BY heat is meant,  that which excites in us the idea of
warmth or hot,  and when the  quantity is lessened, the
idea of cold.  In common language, bodies are said to be
hot and cold; yet the sensations we have on touching them,
do not arise  from the bodies,  but from the passage of heat 
DISCOURSE I.                 51
:nto and out of us. Heat is supposed to be a subtile substance,
flying off from bodies in the finest rays.  By some common
people it is  called  fire,  particularly  when  accompanied
by the emission of light, as in a blaze; by others it is called
heat; and chemists to avoid confusion, call it caloric: by
which they mean that which excites the sensation of heat.
  OUR attention is early  claimed by the changes which
take place in bodies,  when  heat  is accumulated.   These
changes  are  generally termed the effects of heat;  but,  as
some of them are not produced directly by the heat, but by
the affinities of bodjes exercised in the circumstances created
by the  heat—the expression appears to me unexceptionable.
Perhaps,  however,  in common  language,  it may not be
amis3 to  use  it.

  In most cases, heat separates the particles of bodies from
each other, thereby lessening the attraction of cohesion,
and increasing their bulk.  The following experiment will
convey an idea of the expansion which takes place when
heat is increased:  if a  bladder half filled with cold  air, be
carried near the fire, the  air immediately expands, distends
the  bladder,  and bursts  it finally with considerable force.
It is to this expansion, or rarefaction of air, by which its
weight  is  so  lessened, that  it ascends in the air, in conse-
quence of the pressure  of a denser  air, that the currents
of  airs about fires, and the various. winds are produced.
If a bar of iron, which  while cold, precisely fits.aaorifice,
be  heated, the enlargement will be so  considerable that
it will not re-enter the hole.   By making a bar  of .iron six
inches long, red hot, its increase of bulk, will be one twen-
tieth of an inch.   All bodies, however, do not expand alike.
Liquids of the least density  expand the most in the same 
52
DISCOURSE  I.
  temperature.  Thus, atmospheric air will dilate more than
  ether, this more than ardent spirit, this more than oil, this
  more than water, this more than acids, and  these more than
  mercury.   Hence articles which are sold in commerce by
  measurement, particularly spirit,  are  often found much
  smaller in quantity in winter than in summer.  By the ex-
  pansion of metals, cutting instruments are rendered  sharper
  when  heated; and  clocks  and watches vary  in keeping
  time, in consequence of the different expansion of their
  metals, in cold and hot places and  seasons.  As different
  metals expand differently in the same heat, such musical
  instruments, whose  parts are  to maintain  a constant  and
  true proportion,  should never be strung with different me-
 tals, as on this account they may be out  of tune.   Bodies
  which are brittle,  as glass, crack  or break  if  suddenly
  heated or cooled, in  consequence  of this, that the e x-
 pansion,  on one side,  by the heat, is so great as to tear
 apart the other :  hence thin vessels stand heat better than
 thick ones.

   The  enlargement  of bulk is  not the  only effect which
 takes place in an increased temperature.  Other and more
 important changes are produced in many substances, by the
 exercise of their affinities in the states created by heat.   A
 few substances when  heated,  become melted ox fused, and all
 such are termed fusible.  In a higher heat many are converted
 into finer  fluids,  called vapors,  airs, or  aeriform bodies,
 such are called  ecaporable bodies.   We have a striking exam-
 ple of this in ice ;  which in a heat above 32° is fused, or
 changed into  water ;  and this fluid in a heat above 212° is
 evaporated, or  changed into vapor or air.   The degree of
 heat necessary to create that state, in  which bodies assume
 the  aeriform state, depends in some instances very much
 upon mechanical  pressure.  Hence we find, that when the
pressure of our atmospheric air is lessened, as it  is on 
DISCOURSE  I.
53
mountains, or in the exhausted receiver  of  an air pump,
fluids may be made  to boil, or change to vapor, in a much
lower heat.   The  diminution of the bulk of a body, in a
low heat, is  not less general than their  enlargement in a
high heat.   Hence on conveying  vapors in  a cold  place,
as in the tube passing through the tub of a distillery, they
are condensed into fluids.  Perhaps, in most intense  heats,
all bodies might  assume the aeriform state ; and perhaps if
all heat could be abstracted, all the airs and  fluids around
us might become solid.

   In the art of cooking, heat acts by its instrumentality in
lessening the cohesion of the food, thereby rendering it more
nourishing,  and  allowing other and more palatable combi-
nations to take place between the various articles the cook
blends  together.  It would be too disgusting to detail the
various compounds which have been made by cooks for their
idle masters.  But it may be observed, that heat has a most
remarkable effect in increasing the capacity or power of wa-
ter to dissolve  substances,  as we  daily see  in the boiling
pot, where soops, jellies, &c. are  made.  This capacity is
greatly increased when  an instrument which  confines the
steam is used, called Papin's digester.  When this is made
very tight of strong  iron, water may be heated in it more
than  100 degrees beyond boiling water.  In this state it will
dissolve all animal parts; and so excellent a  soop  may  be
made from bones, that it would be well for all families to
be provided with one, as it would save much expence in the
course of a year by superseding the use of much meat.  In
consequence of  the action of heat on vegetables in  water,
whereby they are rendered more nutritious,  Count  Rum-
ford judiciously proposes to  boil all the food given  to do-
mestic  animals, as  much  smaller quantities would then
suffice. 
54
DISCOURSE  I.
   In the art of distilling, heat acts also an important part;
it favors the separation of  the volatile substances, as spirit,
essential oil, &c. from their combinations ; and it is prob-
able, that it causes the chemical combination of the  par-
ticles of the mass, so as to form the substance distilled in
some instances, and  in others  lessens or destroys such a
combination.  Hence, on distilling some  fluids, which are
not  very  intoxicating, a  good deal  of spirit is procured;
but  on  distilling a more intoxicating liquor, as wine, but
little spirit will be obtained.  Yet, this spirit is said to give
the  intoxicating qualities  to all  drinks.   It would be well
for distillers to try in  what heat they can procure most of
the  substance they distil.  The best plan on which a still
could be erected, is that represented in plate 1  fig. .1.  A, is
the body of the still of various sizes.  It should be covered
with mortar three inches thick, made of equal quantities
-of clay and fine charcoal; and then placed in bricks.  The
fire  is applied underneath, but  the  flue  turns  round in a
spiral manner, as shown by the dotted lines ; by this means
but  little heat will be lost.  B, The head of the still, pro-
vided with an  opening at o, to let out the vapor when  in
danger of throwing the head off; the body has also one at
u to supply the fluid.   The head should  be made  of two
thin sheets half an inch apart, between which should be air,
ashes, or fine charcoal, which will prevent the loss of heat.
C,  the  refrigeratory,  or condensing  tub,   filled with cold
water,  through which the worm marked by dotted lines
passes.   The vapor  from the head, is condensed  in  this
worm,  and runs out at the vessel D.
  THE means to ascertain the degree of heat present, are
now to be mentioned.   For this purpose, instruments have
been contrived, called thermometers, which are in common 
DISCOURSE  I.
55>
use.  Fig. 2,  plate 1, represents one of the best kind, call-
ed Fahrenheit's.  The way to form one of the kind, is to
procure a small glass tube, the bore of which is perfectly
regular, to melt one end in the blaze of a candle,  then to
blow  it at the  other end, so that a bulb may be formed.
this being done, the tube is  to be  filled with  spirits of
wine, colored ; or what  is better, mercury.   If mercury
be used, after filling the tube, it is to be boiled for the ex-
trication of all air.  The other end of the glass should then
be  sealed, and  the whole introduced into  freezing water.
Here the mercury parts with its heat, and consequently con-
tracts, or sinks down to a point which should be marked,
and named as  in the plate, the freezing point.  Afterwards
the whole  should be introduced in water boiling under the
common pressure of the air.   The heat of  the water,  will
enter the mercury,  and consequently expand it up to a  cer-
tain height, to be marked as the boiling point of water.  Now
the space between these, is to be  divided  into equal por-
tions, on a body attached to the glass.  The number is not
 of much consequence.  The  French use Reaumur's scale,
 and the English Fahrenheit's, both of which are represented)
 in the plate. Fahrenheit's scale at the freezing point is mark-
 ed 32° ; at the boiling point 212°.   The mercury in the
 tube will rise  or fall in  proportion to the increase or dimi-
 nution of heat. In Fahrenheit's scale (which will be alluded
 to throughout this work, while mentioning degrees of heat)
 the heat of the human body will raise the mercury to about
 98°.   That of a summer's day, in the district of Columbia,
 where  I am about to reside,  from 70° to 90°.   In  mild
 weather the mercury stands  at  about 50°.   In winter it
 varies from 25° to 40°.   At Hudson's bay, and in Siberia,
 the mercury has become frozen, and sunk near 80° below
 the freezing point. 
.56
DISCOURSE  I.
   By the above  thermometer no heat greater than that of
boiling water can be detected.   To remedy this,  an instru-
ment was invented by Mr. Wedge wood, called a pyrometer.
It consists of two pieces of brass, fixed on a plate, so as to
be six tenths of an inch asunder at one end, and three tenths
at the other.   Bits of baked clay, previously prepared in a
red heat, are made of  given dimensions.   These pieces of
clay are first applied to the rule of the above gauge,  that
no mistake may  be made.   Then one of them is to be in-
troduced into the heat  which is to be measured, when it
will contract in proportion to  the intensity of the heat. , It
is then to be taken out, and on applying it to the  gauge,
its contraction will clearly  appear, and thereby indicate the
degree of heat to which it had been exposed.   Each  de-
gree, which it may have shrunk, is equal to  130° of Fah-
renheit.
  HEAT penetrates all bodies in consequence of its strong
tendency to be equally distributed,  or establish an equilib-
rium.  Such is this tendency that no one has been able to
abstract all  the heat from any thing.   It has been stated
that the attraction of cohesion brings the particles of bodies
together, which is an  effect,  the reverse of that caused by
heat.   Now as bodies generally diminish in bulk, in pro-
portion to the abstraction of heat;  and as we  cannot ab-
stract all the heat from any thing, it follows as  an  unques-
tionable,  though singular conclusion, that no two particles
of matter do ever touch each other.  It is in consequence
of this tendency of heat to be  equally distributed, that if
a hot and a  cold  body be brought near each  other, the
temperature of each soon becomes the same.   Hence we
go near the  fire to be warmed,  and  go in the cold to  part
with heat. 
DISCOURSE I.
57
  THE  changes in the temperature of bodies occupy  a
longer or a  shorter time according  to  the nature of the
body: but they always take  place  at  last.  The bodies
which do not reflect much heat from them,  but allow it
to pass through them  quickly, are called good conductors of
heat; and those reflecting  the heat, so that it  penetrates
but slowly, are called bad or non-conductors of heat.  Thus
it is said  in common language, that some bodies are warm,
or retain  the  heat,  and others are cold, or carry it off ra-
pidly.  Thus if we introduce our hand in mercury, and in
water of the  same  temperature, the  mercury  will  feel
coldest,  as it most quickly conducts the heat of the hand.
Hence, if we put the ends of two rods in the fire, of the
same  dimensions, one  of glass and the other of  iron, the
other  end of the iron will soon be too hot to be held in the
hand, while the glass will scarcely be warmed.
  DECISIVE experiments  have  shewn,  that  of  the
solids,  the metals are  the best conductors of  heat, and
the conducting power of these are also found to differ from
each other.  Gold, silver,  copper, iron, tin, &c. are found
the best conductors;  and  next to these stones.   The good
conductors of heat are  used, when it is designed that heat
should be communicated to other bodies for boiling, warm-
ing rooms with pipes, &c.
  THE bad or non-conductors of heat, are numerous and
useful.  Very decisive  experiments have  shewn, that at-
mospheric air, particularly when confined and dry, and  all
other airs, ashes, charcoal powdered alone and mixed with
                          H 
5S
DISCOURSE I.
other substances, feathers, skins of animals,  and coverings
of vegetables, straw,  cotton, hair, eider down, raw  silk,
sheep's  wool, lint or the fine scrapings of linen ;  and in-
deed all fine substances  which retain  the atmospheric air
about them are excellent non-conductors.  By attending to
this subject, important advantages may be  derived, which
are unknown in most places.

   In very cold countries, they have in some parts, windows
with double panes of  glass,  the one half an inch before the
other ; the air between them proves of great service in pre-
venting the exit of  the heat from their rooms.  The same,
probably, it would be well to do in hot countries, which
would prevent the entrance of  heat.   It would probably,
also,  be still better to have a column of air confined under
the coverings of the house, and around the rooms behind
the  plaster.  Vessels  of  iron and  tin  made of two thin
sheets,  the one half an inch or two inches from the other,
are found very useful in cooking, in consequence of not al-
lowing the  escape  of heat.  They would be still better,
particularly the tops of stills, if  fine charcoal or ashes were
introduced  between the sheets.  Our  amiable fellow-citi-
zen, Mr. Moore  of Maryland,  has  made  some  excellent
remarks  concerning the application of this knowledge,
to the construction of the receptacles  of ice, by  which a
given quantity  of  ice  may  be preserved from   melting
longer than one would readily suppose.   A tin vessel, about
 two feet square,  placed in a wooden one so much larger,
 that a space of 3  or  5 inches   may  be left  all   around,
 with this  space  filled  up  with charcoal,  ashes,  hair,  or
 broken glass; will be found to  answer exceedingly well to
 retain ice during the day for family purposes.  The . top of
 this  cooling vessel (or refrigerator)  should be made in a
 similar  way, and to fit  tightly.  In the  middle  of it, a
 small lump of ice should be placed in a cup ; and at the 
DISCOURSE  I.
59
sides  of the cup,  the  butter, milk, meats, &c.  may be
preserved all day as cold as ice,  when the vessel is closed.
By  using such a vessel,  a very  small quantity of ice will
serve  a large family, during the hottest  days.   Ice houses
should be made in dry situations : the inner walls should be
of wood charred or burnt to coal, all  over,  at the  back of
this, a space filled with  air alone, from 1 to 2 feet thick,
or dry straw, ashes,  or  a mixture of equal parts  of clay
and charcoal with it.  An ice house  10 feet  square thus
made, will  preserve ice, longer than  the  largest under
common circumstances.

  A cheap mortar may be made of  about equal  parts of
charcoal and clay, which is an excellent non-conductor of
heat.   Chimneys lined  with this, and surrounded also by
a column of confined air, or  ashes, or pure charcoal, and
made  after the manner suggested by Dr. Franklin,  and ge-
nerally called Rum ford's chimneys, would  be  beyond all
further  improvement.   In an  iron stove lined with the
above mortar 2 or 3 inches  thick, a  greater heat  may be
generated by the combustion of but a small  quantity of
fuel,  than could be contained in  it by  any other means,
without  such a  lining.   The inner part will be found red
hot,  before the outer part  is warmed.  Persons wishing
to reduce ores to their metallic state, might readily provide
themselves with a small common stove, and line  it as above.
They could  readily cause a sufficient  heat to be generated
in it,  to decompose and  change to the pure  metallic  state,
the most infusible ores.   Or  if the blow pipe  be  used,  it
might be made to act on the substance much better,  when
they  are  surrounded by such a mixture.  This  mixture
would be of great service for  covering the body  of stills,
lining furnaces, ovens, brick-kilns,  and all places  designed
to retain heat.   Great quantities of fuel would be preser-
ved by attending to these facts. 
60
DISCOURSE  I.
   Wood,  green  or charred over, is  a remarkable  non-
 conductor  of heat;  and hence  it is proper to have  in-
 struments used about fires with wooden handles.  Count
 Rumford  has  proved  that  barks  of  trees,  peelings of
 fruit, are remarkable non-conductors  of  heat.   This  ac-
 counts for  their not losing their heat in cold weather, which
 was formerly attributed to  a vital principle.   The snow
 covering the ground in winter, no doubt is useful in  pre-
 venting the loss of heat from the roots of  plants beneath.
 The skins  and furs of  animals being most excellent  non-
 conductors of heat,  it  accounts for their  preservation of
 the warmth of  animals  in very cold countries:  those skins
 are warmest  which  have the finest,  longest and thickest
 hair.   Hence the beaver, otter and other quadrupeds, as
 well as water  fowls, well feathered,  retain their  heat in
 the coldest times.   Bears and other animals not frequenting
 the water,  have the fur thickest on their backs.

  The clothing of men is valuable chiefly on  account of
 its retaining the heat of their bodies.  Cotton and  wool
 are better  non-conductors  of heat,  than linen  or  silk,
 and consequently  should be  worn in  winter.   The  scra-
 pings of fine linen, are highly useful in retaining heat,
 and hence, are properly introduced in quilts.  Such as are
 accustomed to sleep on  hard  bodies, and  cannot purchase
 a bed  and  clothing,  would  probably  sleep  much more
 comfortably, if  they would have a long  case, open  only at
 the end  charred  in the inner side,  and lined with some
 cheap  article, in which they could introduce their bodies,
without fear of cold at night,  keeping their heads out.

  Count Rumford,  in his essays on  heat, states  that  all
 fluids are perfect non-conductors of heat;  in consequence
 of noticing, that when heat  enters  them, a  motion takes
place, which one would naturally expect who knew the fa- 
DISCOURSE I.
61
cility with which  fluids  could  be agitated.    However,  it
matters very little, since it is a fact, that heat passes through
them. The Count found, that by introducing heated bodies
into fluids, the heat was not communicated  downwards;
also, that ice melted 80 times more quickly on the top than
at the bottom  of hot water.  This must appear very evi-
dent to any one knowing that heat rarefies bodies in which
state they ascend.   He  thinks that he has  discovered that
the steam of water is a non-conductor of heat.   That it is
a non-conductor, might long since have been inferred,  from
the fact, that it requires much longer time, for a drop  of
water to evaporate from red hot  iron than from that which
is less  heated.  Hence it has been proposed,  to  ascertain
the degree of  heat present,  by  (he duration of  a drop  of
water on hot iron.  Mr. Chaptal states,  that the water is
longest retained on the hotest iron,  in consequence of  a de-
composition it is supposed to  undergo.   But this is erro-
neous ;  as, we perceive the water bouncing about in va-
rious directions.  It appears to  me, that the retention of
the water can  only proceed  from  the formation  of  steam
underneath it, thereby  preventing  the heat from entering
the inner part, and causing the drop to move in various di-
rections.   In this idea,  I am  supported by a fact, which
occurred lately among  some school boys.   One of them
heated  a poker red hot, and then  several  times licked it
with his tongue, to the  great  astonishment  of the rest.
Here the steam, suddenly formed between  the tongue and
the iron, prevented the heat from burning him.   On put-
ting down the poker,  after it had lost  the red heat, ano-
ther of  the boys,  from the love of imitation or  of  show-
ing his courage, took  it up and repeated  the.experiment.
The heat, not being sufficient  to  form steam,  penetrated
his tongue, and burnt  him  so as to make him bellow, to
the no small diversion of the bystanders. 
62                 DISCOURSE  1.
  HITHERTO,  I have been speaking of that heat which
is free from combination, acts on our senses,  and  is con-
sequently called  free,  uncombined,  sensible, radiant, or
thermometrical heat.  Dr. Black  of Scotland, made some
important experiments,  by which he discovered that this
sensible heat was absorbed  by some bodies,  particularly
when they were changed from the solid to the fluid state:
when absorbed by bodies it chemically combines with them,
so that it neither  acts on our senses  or on the thermometer.
In this state  it is  called solid,  combined, or latent heat.
An idea of this may be formed from the following experi-
ment : take a pot of water,  allow it to remain on  the fire,
and constantly to boil.   The heat will be continually  im-
parted from the fire to the water; yet it will be found that
neither the temperature of the water or of the steam will
ever exceed 212°.  Ice in a warm  room will, while melt-
ing, absorb heat (or produce cold); yet its temperature
will not be increased above the melting  point 32° until the
whole  is melted.  If  salt and water, the temperature of
each being  the  same,  be added together, while  the salt
melts,  there will be considerable coldness, or absorption of
heat.  The only manner  in which  this loss  of  heat, in
these and similar experiments can be accounted for,  is by
its chemical union with  the substances :  it is therefore pro-
perly termed latent heat.    As different bodies unite with
different quantities  of heat, their power of uniting with it
is termed their capacity for heat; the whole quantity of heat
uniting to a body is termed  its absolute heat.  The expe-
riments to ascertain the absolute and specific heat of bodies,
are neither accurate or  of much consequence.   It is gene-
rally true that all bodies, whenever their conditions or states,
are in  any manner  changed,  have a corresponding change
in their capacities for heat.   Hence they either give it up,
which produces  warmth, or unite to it, which  produces
coldness.   When  they  are changed  from the solid to the 
DISCOURSE  I.
63
fluid, and from the fluid to the aeriform state, generally
they unite to  or  absorb  heat.  That this  is the  case, is
proved by the  fact that they may  be made to give up this
heat again, as we see instanced in steam ;  which every one
knows gives up heat when condensed to water, which last
gives more up when reduced to the state of ice.  Generally
all bodies, when  changed from the aeriform to the fluid,
and  from this to the solid state, give up  sensible heat.
However, there are  striking exceptions to  this, as some
bodies undergo very material alterations without any change
in their capacites for heat.   All the changes in  heat, with
which we are  acquainted, from the most  intense heats to
the extremes  of cold,  arise solely in consequence of the
changes in the capacities of bodies for heat.  The  means
of varying these capacities  may be Very properly consider-
ed in this place.   And first, of diminishing heat so as to
produce COLDNESS.

   In nature we find coldness  very generally produced by
evaporation, as the fluids  are changed into vapors, they
absorb the  sensible heat, and carry  it off.   The  dryness
and agitation of the air promote this evaporation very con-
siderably.  The coldness of summer days frequently arises
from the sudden  evaporation  of water from wet  lands,
and it is in consequence of  the evaporation of the sweat of
laborers, (particularly  the  blacks, whose skin favor  the
generation of  warmth, which promotes perspiration) that
they are enabled "to work in the hottest weather,  exposed
to the  sun.  The  same evaporation, has  enabled  persons
to remain minutes in rooms where  the heat was sufficient
to boil water  all  around  them   The scorching   winds
within the tropics, are prevented from suffocating  travel-
lers, only by covering their heads with wet  cloths; which
if too  wet,  will by the  quick evaporation  of the water,
become insufferably cold.   Sprinkling water on the  streets, 
64                 DISCOURSE I.
cools them on the same principle.   In the East Indies, ice
is frequently made in pits dug in large open plains, at the
bottom  of which, dried  straw or  stalks of Indian  corn
are placed ;  upon these  they put  a number of  unglazed
pans,  made  of so porous an earth,  that the water  with
which they are filled exudes through them.  These pans
are filled  towards  evening,  in  the  winter,  with boiled
water,  and are left  tranquil till  morning, when  more or
less ice is  found  in them.   The  quantity depends  on the
temperature  of the air; there being more found in dry and
warm weather, than in cloudy.

   In Spain  half baked  earthen pans are used to contain
water.   Their outside is kept wet by the water which fil-
ters through them,  and  although they are exposed to the
sun, the water in the jar becomes as cold as ice.  I have
thought that it would be very advantageous to have a wind
machine,  something like a Dutch fan, to cool our waters
in summer.  If at the mouth of such  a one, tin vessels con-
taining water and covered with wet rags, or unglazed ear-
then vessels, with the water exuding through them, were
placed,  and  the dry air of the warm side of houses, caused
to pass quickly  over them, there is no doubt but that the
evaporation would be such as to cause considerable  cold-
ness.   Perhaps,  ice might  be  made in this manner.  At
all events, our drinks might be so cooled as to supersede,
probably,  the use of ice-houses.  In China it is common to
cool wine and other liquors, by  wrapping the bottles con-
taining them in wet woollen rags, and exposing them to the
sun.  The blacks, in parts of Africa, have very cool water,
in consequence  of hanging it up in leather bags in the
shade, where the evaporation becomes considerable.

   On putting a  little ether  on our hands, we immediately
have the  sensation of cold, from its quick  union with the 
DISCOURSE I.
65
 heat of the hand.   By inclosing water in a thin  glass ves-
 sel, and  dipping  the glass in ether, and  then  moving  it
 briskly to accelerate the evaporation, ice will in a few mi-
nutes be formed.

   When  some substances unite together, they acquire a
 capacity for heat,  and absorb great quantities in some in-
 stances, so as  to produce  the most  intense coldness.  In
 the West-Indies, wines are generally cooled by introducing
 them into the following cheap mixture:  Of Glauber's salts
 16  parts,  of saltpetre 10 parts, of  sal-ammoniac 11 parts,
and of  water 32 parts.   The  coldness, after this combina-
tion, will be considerable ;  but not so great as that from the
following, which are extracted from lists containing many
others of the kind.
MIXTURES. [THERMOMETER SINKS.	
Sal-ammoniac, 51 ^ Nitre, 5 V 3 Water, 16 3 ?	From 50° to 10°.
Glauber's salts, 3?*$ \ „ „0 ^ ao Diluted nitric acid, 2 j £ ^ 5° t0 3 '	
Equal parts of snow and 1 common salt. 1 '	
Equal parts of snow and diluted nitric acid.	From 0° to 46°.
I»i1utedsu,Ph.acid>10,1| From 6f, ,0 91,	
Dry muriate of lime, 3 ") *g Snow, 25 g	From 32° to 50°.
I 
66                 DISCOURSE I.
MIXTURES.	THERMOMETER SINKS.
Potash, 4") ^ Snow, 33 £	From 32° to 51°.
Muriate of lime, 2 ~) *g Snow, 1 3 S	From 0° to 66°.
Equal parts of snow and diluted sulphuric acid.	From 20° to 60°.
Muriate of lime, 3") !£ Snow, 1 3 p	Fiom 0° to 73°.
  Mercury may be frozen by all the mixtures, bringing the
thermometer 40° below 0°.  They are so cold that the  hand
is quickly blistered if introduced in them.

  We are now to mention the means of generating heat.
They may be divided into mechanical and chemical.   The
mechanical means operate merely by squeezing the sensible
heat out of the body.  By the sudden  pressure of  atmos-
pheric air, heat may be extricated in sufficient, quantities to
burn some substances.  Most  of  the metals may be  made
almost  red hot, by  hammering them quickly.   In some
places powder is flashed, by  employing a  strong man to
strike an iron briskly till heated for the purpose.  The heat
following the  friction of hard bodies against each other,
appears to arise, in the first  instance, from  the  sudden
pressure of the surrounding substance.  Flint struck against
steel generates a  heat sufficient to cause the steel to  melt,
which afterwards burns,  as  maybe  observed by catching
the bits as they come off on paper.   Fires are quickly kind-
 led by rubbing dry sticks against each other in some parts; 
DISCOURSE  I.                 67
an iron plate may be made  red .hot, if  much pressed on
another, and moved backwards  and forwards.  Carriages
and mills, are sometimes  set on fire by the heat collected
during the turning of the  wheels.   Count Rumford made
water boil by boring cannon in it.
   THE chemical means of exciting heat, or in other words,
the means of diminishing the capacities of bodies for their
latent heat, are now to be considered.  On collecting to-
gether the rays of the sun, by means of a lens, it is well
known that great  heat may be produced.  Diamonds  have
been burnt by the heat so produced.   This heat does not
come from the sun, since  it would require some time for it
to penetrate the glass.   It  is, in all probability,  caused  by
the union of light with the body on which it acts, whereby
the capacity for heat is lost.  On the same principle,  great
heat may also be created by the electric and galvanic fluids,
so as to melt the hardest bodies.

   Water may be made  quickly to boil,  if inclosed  in  a
tube, which should be placed in a vessel containing water;
to which water, sulphuric acid is to be added gradually. Spi-
rit of turpentine will quickly blaze,  if a small quantity of
the nitric acid be poured on it.   Many other combinations
of the products of art, are characterized  by  the emission
of heat, which it would be useless to mention in this  place.
Many combinations in nature take place, which are attend-
ed by  the emission of  heat.  We frequently  see it during
the putrefaction  of animal  and vegetable matter in  dung
heaps.   Stacks of hay  are sometimes  burnt unexpectedly
by similar  chemical changes.  Particularly about volcanic
places great heats are thus generated. Sometimes the earth,
in parts of  Italy,  is so hot  as to burn the feet of passengers. 
68
DISCOURSE I.
And lastly,  the burning of volcanoes arise  from the same
cause—a change of  capacity for latent  heat.  It may not
be improper here to  observe, that the phenomena attending
volcanoes arise,  probably, from the chemical action taking
place between iron,  sulphur, and water.   These three sub-
stances are common about volcanoes ; and by mixing them
together at any time we find heat will be generated.  What
still more confirms this, is the artificial volcano which may
he formed by these substances, and which exactly resembles
in miniature the great volcanoes.  If equal quanties,  of the
filings of iron and sulphur, be made into a  paste with wa-
ter,  and from 30 to 100 weight of it be covered  5 or 6 feet
under the earth,  and well pressed down,  in a few hours an
action will commence :  smoke and fire will arise, the earth
will open and lava will be emitted.

   It is chiefly by the  combustion,  or  burning of bodies,
that sensible heat is emitted for the common purposes  of life.
Every one knows that  for this combustion  to  take place,
the presence of atmospheric air is necessary.  The sensible
heat which follows the process, is probably given up  by the
body burnt, as well as  the air which disappears.   It cannot
be  accurately determined how much heat is  given  out
during combustion.  But it has been ascertained, that  the
largest quantities are yielded while an air, called hidrogen
air,  mineral  coal, wood,  &c.  are burning.  The  largest
quantity of  heat, which has  been  yet  produced, was by
Mr. Hare, an ingenious chemist of Philadelphia.  On learn-
ing, that most heat was thrown out during  the combustion
of hidrogen  in  vital air,  he had  a quantity of the  two
airs collected (the manner of doing which will be hereafter
stated)  and  introduced them  in a double bellows, each
pure and in distinct apartments.  The tubes, leading from
these apartments,  opened at the same  place,  where fire
being applied, sufficient heat  was generated to melt the 
DISCOURSE I.                  69
most  infusible metal, platina, and  several substances,  ne-
ver before fused.

  The theory,  to explain what takes place during combus-
tion,  is perfectly simple.   The reader should  be apprised,
that our atmospheric air,  is compounded of two airs ; that
three  fourths of it are of no service in supporting combus-
tion,  and that it  is the remaining  one fourth,  called vital
or oxigen air, which is  the chief agent in the process—
Now  this vital air contains in a latent state great quantities
of he3t and  light; the capacity for which is  lost more or
less when die air combines with other bodies.   This being
recollected, the following must appear more  plain.  Heat
is applied to a body;  it puts  that  body in a state in which
it attracts the vital air; to which it unites,  forming a new
substance, which not having  the capacity to  retain  the
latent heat and light, the  ingredients had previous to union,
these are  consequently set at liberty in the form of blaze.
This  is the  general explanation of the process of combus-
tion.

   We will now consider more particularly the  burning of
wood.  Fire is kindled at one part, the heat penetrates it,
converts it  into charcoal, and rarefies this charcoal into a
kind of air.  In  this  state,  the air is quickly attracted,
and an union follows, whereby heat  and light are set at
liberty.  The heat continues to penetrate the  wood,  and
 creating the necessary state for its union with  air,  till the
whole disappears.  The  rapidity of  the  process,  is  also
increased, by the sensible heat,  which rarefies the sur-
rounding air;  in consequence  of which,  it  is quickly
removed by the pressure of a denser  air,  which still more
 favors the chemical combination.   The reasons then must
 appear evident, why there is a  circulation of air about fires,
 and why it is indispensably necessary for a free combustion 
70
DISCOURSE  I.
or union between the air and  coal.  Moderately blowing
the fire, by pressing the air closer to the wood,  promotes
combustion ; blowing it  too  rapidly extinguishes  it, by
carrying off the heat before it creates that state in the wood
necessary for its union with air.  Water extinguishes it, by
carrying off part of the heat, in the form of steam, and by
preventing the contact of air.

  During the combustion of mineral coal, we perceive how
necessary the agency of heat is to create that state, in  which
the substances in it capable of burning, exert their affinity
for oxigen.   We have,  also,  a striking  illustration  in the
burning of a candle.  In a little heat,  the tallow first be-
comes fluid,  then it is drawn  up by the wick, where more
heat existing it expands,  and  as rising  unites  to the  air,
thereby causing the blaze. Instead, therefore, of saying that
combustion was the consumption of a body, we should define
it, "the formation of anew compound, through the agency of
heat, attended generally with the emission of heat and light."

  When,  instead of allowing a combustible  body to burn
slowly in the air, we add to it a substance, as common nitre,
which contains a great deal of light and heat in the solid
state,  then on applying fire, the union is quick, and the e-
mission of heat and light instantaneous.   This heat rarefies
the bodies so suddenly,  and with such force as to produce
a loud noise and great effects :  this  is called detonation.  We
have an example in the  combination of sulphur, charcoal,
and nitre, forming gunpowder.  On applying heat,  a che-
mical action ensues instantly, and is followed by the  vio-
lent effects, usually noticed in consequence  of the  expan-
sion of  airs,  by the sensible heat which it liberated.

   Besides, by the above  methods we have sensible heat, by
the condensation of  vapors.  When we lay a cold body 
DISCOURSE  I.
71
down in summer, it absorbs sensible heat from the water in
the air, which then becomes condensed  in  the  form of
drops on.the surface.   It is, also, in consequence of part-
ing with sensible heat,  that we find water condensed on the
windows and walls of  houses.  To the same cause, must
be owing the collection of  the vapors in the air, at first to
form fogs,  then  clouds,  dews,  rain,  snow,  and  hail.
What  becomes  of the sensible  heat in  our atmosphere,
when water is condensed, and what is the immediate cause
of the  condensation, must be interesting questions.  It ap-
pears to me to arise from chemical changes in the air, which
maybe wrought by various causes,  whereby the capacity of
the air for latent heat becomes so  increased, as to attract
it from the water.  Every one knows, that the electric fluid
is  collected in various quantities,  at various times in the
air ; and that when it is present it causes the  extrication of
heat.   Now, it is very  probable,  that in consequence of
collections of  electricity  in the air, its capacity for heat  is
lost;   then  when the electricity  escapes  slowly, or in
large quantities,  causing thunder, the capacity for heat  is
restored to the air, which consequently absorbs the heat
from the surrounding vapor,  thereby converting it info wa-
ter,  or rain, hail and snow.  Hence we see the reason,
why in hot countries,  lightning, rain, and hail so generally
go together.  Light  has  no doubt,  also,  some influence in
lessening the capacity of the air for heat,  as we know that
heat is thrown out when light is collected.  But to descend
from clouds  to pot-boiling,  we have already  stated  that
steam  contained latent heat, which  was given up or con-
verted into sensible heat when  it was condensed.   Count
Rumford has particularly attended  to  this,  with  a view to
economise in the use of  fuel.    He proposes to have the
steam  conveyed through  pipes, where it will condense, and
give out the heat to  which it united,  during its conversion,
for the purpose of cooking.  Unquestionably this would be 
72
DISCOURSE I.
of great advantage.  The steam from a small kettle of water
is sufficient, if properly conveyed over the articles, to cook
any vegetable or  animal substance  in common  use.   In
some houses they  have already got in the practice of using
steam altogether ; so that the boiling of one small pot serves
for dressing all the meats,  and most of the vegetables  used
in a large family.   In common, it might answer to have an
apparatus for cooking,  on the plan  of that represented in
plate  I, fig. 3.   A is a box, which should  be three or  four
feet in length and breadth, and only one in height.   It may
be constructed of what materials the maker pleases to em-
ploy.   It would answer very well to have it of thick plank,
which has  been charred or burnt over  in the inner side, to
prevent the quick passage of  the heat; or,  if  it were made
of brick, it should  be lined with a mortar composed of clay
and charcoal.   In this box there should be a small division,
of about one foot square, made of tin or very thin iron : Or
it might answer to  have a small box of  the kind, let down
in the larger one, and supported about its brim  on the top
of the large one.   This small box, or division,  should be
called the baking box or apartment. B is a small pot, holding
two or three gallons of water, which  is connected to the
cooking box, by the pipe C, which is about two  inches in
diameter, and two feet long.  This pot is to have a cover that
will fit very tight.  Things being thus arranged, the  meat
and most vegetables are to be introduced in the cooking box
A; and the bread and deserts should be, also, placed in the
baking apartment.  On applying fire at the pot  B, it boils
and the steam enters by  the pipe C into the  box A, and there
condenses,  giving  up its sensible heat  which acts on the
meat, and  passes through the tin and bakes the bread.   A
small orifice is to be left at the dotted end of the box for
the escape  of the steam. When it is designed to make soop,
the articles can be readily boiled in the pot  B, which should
have  its sides covered with charcoal  mortar, to prevent any 

Tie-. 2.
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PuMuhdly Knrlan <(- Brannan ^\?S^or/t
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DISCOURSE  r.
73
 loss of  heat.   Before  the  small fire, any  article  can be
 roasted with facility, as  the heat reflected will be consider-
 able.   And thus by a little attention, every article of food
 can be well cooked, with but a small consumption of fuel,  and
 without  injuring the health  of persons by  standing over
 large fires.

   Lately the ingenious Mr.  Deneal of my native village,
 Dumfries in Virginia, has invented  a machine  by which
 crackers  are  safely  baked by steam.   No  one can  doubt
 that any  kind  of bread,  inclosed in thin vessels of  tin
 or  iron,  tightly stopped,  might be safely and well baked,
 if exposed to the action of steam. In some cold  countries
 they have but one fire place in their houses ;  from which^
 pipes  are carried through all the rooms for warming them.
 Probably it would be better  if  such  pipes conveyed  steam
 instead of smoke.

  Travellers desirous of kindling fires of nights, generally
 do  it  by means of the flint and steel.  They might kindle
 them  more expeditiously, by providing themselves with two
 small  vials, the one containing  nitric acid (the aqua fortis
 of the shops) the other the spirit of turpentine. These must
be mixed in small quantities, and cautiously;  as, the blaze
 following is considerable. Sometimes vials containing a very
 combustible substance (phosphorus) are used.  The means
 of preparing them, will  be  mentioned  when considering
 phosphorus.
  BEFORE dismissing  the  subject of  heat,  it  will  be
proper  to  notice an  opinion delivered by the  great Dr.
Black,  which has since his time been published in all the
systems of chemistry, as if its truth had been established.
                          K 
7*                  DISCOURSE I.
The doctor was the first who noticed the  fact, that when
substances were changed  from  the solid  to the fluid, and
from the fluid to the aeriform state, generally they absorbed
sensible heat,  or rendered it latent.  Also, that when airs
or fluids were rendered solid, they gave up  sensible heat.
Not satisfied with  this important discovery, he and all the
chemists since his time have stated, that the cause of the solidity
is the loss of heat; and that the cause of the fluidity is the union
with heat: Hence he  calls the latent heat caloric  of fluidity.
This appears to me, for several reasons, an erroneous doc-
trine, or rather assertion.  An incidental circumstance, the
absorption of  heat, which must proceed from  a capacity in
the body previously acquired, is considered as the cause  of
the new properties  of fluidity, &c. !  What must  have
given the body a capacity for heat ?  And why may not the
cause, which gave the capacity, be the cause of the fluidity ?
The doctor's  opinion must appear erroneous from the facts,
 that the fluidity of bodies is not proportionate to the quantity
 of latent heat; and that their  solidity is not  proportionate
 to the loss of heat.    A few experiments will shew these
"truths.   If on a piece of chalk, you pour sulphuric acid,
 immense quantities of air will  escape, although  no  absorp-
 tion of heat or coldness  will be produced.  If charcoal be
 burnt in pure air,  great quantities of heat will be set free;
 yet the air formed during the combustion is  as  fluid as the
 air which disappeared.  Nitric  acid, in a strong heat, is con-
 verted into two airs of great bulk,  which contain no more
 latent  heat than the  acid did.   On adding salts to water,
 great quantities of heat are absorbed, yet the fluidity of the
 whole  is  not increased.   When  water  is made  solid,
 by freezing,  but little heat is  extricated; yet,  when it is
  made solid by an union with quick lime, as in slacking lime,
  then much heat 19 extricated.  When we bring two airs to-
  gether, the ammoniacal and the muriatic, they form a solid
  yet throw out no heat.  The«e and other similar facts, j ustify 
DISCOURSE I.
75
the conclusion that solidity and fluidity do not, as Dr.
Black supposes,  depend on the  quantities of latent heat.

   After considering this subject, I am decidedly of opinion,
that the fluidity and solidity  of substances, depend on the
same cause which varies their capacities  for heat; and this
is  the exercise of the particular affinities  of the body, in the
circumstances existing in the different degrees of heat.

   If this be  admitted,  we shall no longer be surprised at
the above  facts I have mentioned, nor at the following;
that water while freezing has its  bulk increased, although
it  parts  with heat;  and that iron,  bismuth and zinc,  when
melted, and  some clays in strong  heat,  really contract in
bulk.   Nor should  we  be astonished at  any of the effects
which take place,  as they all proceed  from the exercise of
the affinities  of the bodies,  in the states  created, the nature
of which we can only learn by  experience.
  HITHERTO I have spoken of heat as a distinct sub-
stance:  It must  now be observed, that the philosophical
world has long since been divided on this subject.  Some
have contended that there is no  such matter as heat; and
that all  the phenomena proceeding from what is supposed
to be heat, arise from a peculiar mechanical motion.  Others
have maintained,  that there is a particular substance, inde-
pendent of other matter, which  excites the sensation  of
hot when it enters in us,  and the sensation of cold when
it comes out of us.   The arguments  adduced in support of
each doctrine have been ingenious but  not conclusive.  On
the one hand, it  has  been found, that  bodies weigh less,
while hot than when  cold ; and that some contract while
heated; and that others,  as  ice, enlarge  while  freezing. 
76
DISCOURSE  I.
This diminution of weight arises from the escape of heat
from the bodies, whereby the  surrounding ai" is prevented
from pressing on them;  and the other effects arise as before
stated from  the peculiarity  of the  affinities  exercised  in
heat.   The argument deemed the best in establishing the
materiality of heat, is the fact, that some bodies reflect it as
light.   But this is  not  conclusive,  as motion  may  be re-
flected as well as light, as is instanced in the echo of sour.ui.
In order to determine this long agitated question,  I institu-
ted the following experiments : the first two of which were
published in the Medical Repository,  addressed to the cele-
brated chemist, Dr. Mitchill, now  of  the  United  States
senate.

   In two vessels of glass, tightly stopt, I accurately ascer-
tained the weight of some water, and  some neutral salts.
The salts of the one were then added to the  water  of the
other,  and the  vessels again stopped.   As the salts  dissol-
ved, great quantities of heat were  absorbed.   When the
absorption ended,  near the fire I wiped away all the  water,
and found on weighing  the whole again, that there was an
increase of weight proportionate to the quantity of articles
used.   For  each ounce of the  mixture,  there  was an in-
crease of weight of rather more than half a grain.

   Two large vials, each half  filled,  one with water, and
the other with sulphuric acid, were tightly stopped, and cau-
tiously weighed.   The water was then  poured to the acid
hastily, to prevent evaporation, and the vials again stopped.
The sensible heat thrown  out  was considerable; and after-
wards on weighing the whole I found the loss of weight
more  remarkable than the gain in the first experiment.

   In the third instance, in an  open mouth glass  vessel,
holding one quart,  I introduced  a  six  ounce  vial,   filled 
DISCOURSE  I.                 77
with sulphuric acid,  to the cork of which a wire was  at-
tached,  which was kept out of the mouth of the  vessel.
The bottle was then filled with water,  stopped with sealing
wax,  and accurately weighed.  This being done  by  means
of the wire, the cork was extracted from the vial, and  the
sulphuric acid, gradually uniting to the water, gave out a
great  deal of sensible heat.   When  this was  ended,  on
weighing the whole again,  the loss of weight was still more
remarkable.

  The variations of weight in these  experiments,  which
were  made  as carefully as  I could make them,  must have
proceeded from the variations in the heat.   Hence it must
be admitted that heat is matter. 
DISCOURSE  II.
    WE are now to consider the three remaining uncon-
finable bodies, light, electricity  and galvanism.
OF  LIGHT.
   ALL of us know that it is through the agency of light,
we see the surrounding objects; and that this light is emit-
ted by the heavenly bodies, as well as by a few around us,
particularly those  which are burning,  or  undergoing other
chemical changes.

   Philosophers have advanced different theories concerning
the nature of this light.  By some it has been considered
as a quality of matter,  given by the motion of the heaven-
ly bodies; by others as a modification of heat;  but the ma-
jority, with the great Newton at their  head,  consider  it
as a  substance consisting of  small  particles,  constantly 
DISCOURSE  II.                 79
separating from luminous bodies, moving in straight  lines
with inconceivable  velocity,  and rendering objects visible
by coming from them and striking  the eye.  That light is
matter,  is shewn by the facts,  that  its motion is progres-
sive;  it maybe stopt, or its course  changed; it may be
condensed into a smaller,  or dispersed over a larger space ;
and it is also subject to the laws of attraction,  as is shewn
by its influence in decomposing chemical compounds, and
from its being attracted, when  introduced in a  dark  room,
through a small orifice,  by any body  which is brought
near it.

   In  order to render what will be  said on this subject in-
telligible, it will be necessary to explain a few terms which
philosophers  use.
   A ray of light  is an exceedingly  small  portion of  light,
which comes from a luminous body.
   A beam of  light is a collection of parallel rays.
   A medium  is the body affording a passage for the rays of
light.   Such bodies may be called conductors of light.
   Diverging rays are those which come from a point, and
separate from each other.
   Converging rays are those which tend to a common point;
and the focus is the point to  which the converging rays are
 directed.

   The light emitted from bodies passes in direct lines, un-
 less directed from its course by other  substances.   Such
 substances as allow the light  to pass through them, as glass,
 are called transparent bodies; they might also  be  called
 conductors of light.  Although the light passes through such
 bodies, yet when it comes in an oblique direction, they di-
 vert it  from  a direct course, or in other words refract  it. An
 idea of the refraction of light, may be formed by putting a
 straight stick in clear water, exposed to the sun.  In con- 
80
DISCOURSE  II.
 sequence of the refraction of the light, the stick will appear
 crooked. Newton noticed, that bodies refracted light in pro-
 portion to their density; but if the medium through which
 it passes, be combustible, the refraction is greatest. This led
 him to conjecture, from the great refracting power of dia-
 monds, that it was combustible;  and, also,  that water con-
 tained a combustible  ingredient;  which conjectures,  are
 since proved to be correct. As our atmosphere has the power
 to refract light, the sun sets and rises sooner than appears
 to spectators.  As water refracts it considerably, and as diffe-
 rent quantities  of it are suspended in the atmosphere at dif-
 ferent times, may it not be the cause of a difference in the
 length of days, by variously refracting the light ?  Such
 transparent bodies, as have their surfaces  convex, as the
 common glass lens, cause the rays of light to converge to-
 gether, and such as are concave have a contrary  effect.

  After  light passes through transparent bodies, it strikes
 against those which are not so, and which consequently are
 called opaque :  they might also be termed non-conductors of
light.  On coming against these it is thrown off,  or reflect-
ed,  and  in proportion  to the reflection, is the brilliancy of
the body.  When the ray of  light strikes the body, it is re-
 flected, so that the angle formed on one side, called the an-
gle of incidence,  is equal to the angle formed on the other
side, called the angle of reflection.

  Opaque bodies reflect light in  all directions.   The light
reflected from the objects we see, penetrates the transpa-
rent humors of our eyes, from the convexity of which, the
rays of light are converged together.  They then strike  a-
gainst  the  nerve of the eyes, and excite motions,  which
when communicated to the brain,  constitute  our ideas of vi-
sion. All our ideas of color proceed from the motions thus
excited in the nerves  of  our eyes.  Therefore one object 
                   DISCOURSE II.                81
 differeth in appearance from  another, inasmuch only,  as
 there is a difference in the  action excited by the light re-
 flected from  them.  Hence if we suddenly strike the eye,
 we have the idea of a flash of light, in consequence of the
 pressure exciting an action in the nerve of the eye, like
 that which light would do.

   By what means is it that light excites  in us ideas of the
 different color of objects ?  In order to solve this question,
 Newton supposed that light was a compound body, each
 ray of which was formed by the union of  seven rays of a
 different kind. This supposition, now almost universally re-
 ceived as correct doctrine, is grounded on the following ex-
 periment :  on taking an  irregular shaped glass, called a
prism, and applying it before a small  hole, where a ray of
 light enters in a dark room, the  ray will  seem divided into
 seven different parts, the lowest being red, above this  o-
 range, then yellow, green, blue,  indigo, and lastly violet.
 He  moreover found, that these seven  different parts  of
 light, when  united together, formed the original or white
 ray.  Upon  this  experiment, he stated, that the color of
 bodies depended on the absorption of some rays  and reflec-
 tion of others.  For example, that the  redness of a body
 is in consequence  of the absorption of all the rays except-
 ing  the red;  that  yellowness  is in consequence of the ab-
 sorption of all the rays but the yellow, and the same of the
 rest of the colors.   He also  added,  that whiteness arises
 from the reflection of all the rays ; and that blackness arises
 from the absorption of all of them.

   It appears to me, that the experiment on which this the-
 ory of  the composition of  light is founded, is by no means
 conclusive.  That light on passing  through an irregular
 shaped glass, should be variously affected, and consequently
                           L 
82                 DISCOURSE II.
excite corresponding motions in our eyes ; that one part of
the glass should so act on the light,  as to make it excite the
idea  of  red, that another part of the glass should cause the
light to excite the idea of green,  and so on of the rest of its
parts, does not appear surprising.   Nor is  it  astonishing,
that an union of these rays, so acted on, should be followed
by the  restoration of the original power of the ray.  But,
even, if the doctrine of the composition of light were true,
it could not account for all  the color of bodies.  To sup-
pose that blackness is  in consequence of the absorption of
all the light,  must be absurd ; since, it is only by the re-
flection  of light,  that we are enabled to  see black bodies,
and since bodies,  which  are transparent, and of course al-
low the light to pass through them, are very far from being
black.   That whiteness does not proceed from the reflection
of all the light, is shown by the circumstance, that the white-
ness  of bodies is not proportionate to their reflection of light.
Hence,  mercury, polished iron, and other  metals, reflect
more light than the whitest paper.

  Since the above theory of the composition of light was
advanced, philosophers thinking it, I suppose, too simple,
have added to it considerably.  The seven rays, which  I
have named,  they call colorific,  to  distinguish them from
two  other kinds they have been pleased  to name, the one
calorific,  because exciting heat;  the other de-oxidizing, be-
cause capable of separating oxigen from some bodies. The
facts, that certain modifications of  light, expedite the ex-
trication of heat,  and oxigen,  do not justify these theories ;
and, consequently, I shall here leave them,  under the be-
lief that they are too complex to be true.

   As then it has not been proved that light is a compound,
and as it is contrary to the uniform  simplicity  of  nature, 
                   DISCOURSE II.                 83

that it should have been  made so, I conclude that it is like
heat,  a simple elementary  substance.  Of course, the va-
rious  colors of objects, cannot proceed from  the absorp-
tion of some rays and extrication of others    Our ideas  of
the color of bodies,  appear to depend solely on the peculiar
modification  or motion of light,  given by the refecting surfaces.
The  reflecting surfaces, probably receive their  respective
powers, in consequence of peculiarities in their mechanism,
or organization.   For example, our idea of the redness of
a  brick before us, is in consequence of a peculiarity in the
mechanism of the brick, enabling it so to act on light, as
to cause the light escaping, to excite in our eyes the motion
constituting the idea of redness : and the same of all  other
colors. Now, as bodies vary more or less in their organization
 or mechanism or construction, it follows,that they should give
 the various qualities to light,  enabling it to  excite the  great
 variety of  ideas  of color.  If this be correct, in order  to
 give one body the color of another, we have only to give it
 a similar reflecting surface. The means of doing this, which
 come under the heads of dying and painting, will be  men-
 tioned elsewhere. It may, however, be here remarked, that
 the  motion given to  bodies  called green,  experience  has
 shown to be least pernicious to the eyes ; therefore,  a pre-
 ference should always be giveri to green colors.

    The above theory is supported by the following facts : by
  various mixtures, acting chemically, the light emitted  du-
  ring combustion, can be made to assume  particular colors,
  or  in other words, excite particular actions in the eye, as
  red, green, blue, &c.   The light coming  through a round
  glass vessel,  containing one  colored fluid,  may be made to
  excite  different  ideas of color, by varying the position of
  the vessel.  In the clouds we also  sometimes seethe most
  beautiful  modifications of  light, from a  scarlet to a  sky
  blu<i. 
84
DISCOURSE  II.
   As light, like heat, is emitted during the chemical action
of bodies on each other,  it follows,  that like heat, it had
been combined with them, forming one of their solid com-
ponent parts.   When so united it should  be called  latent
light.  The capacity of bodies to unite with it, varies con-
siderably; some containing much more of it than others.
Fluid  substances appear to contain more of it, as well as
heat, than solids;  however, the  fluidity  we  should  not
attribute  either to  the light or  heat:  yet  we find that
when  bodies  unite with  an unusual  quantity of  light,
their capacity for heat is diminished.  Every one  knows,
that the light of the sun  causes  an increase  of  sensible
heat.  Dr. Franklin long since noticed, that black bodies,
exposed  to light,  emitted more heat  than white  ones.
Hence the advantage of wearing white clothes in summer.
It has  already been observed,  that most  intense heats have
been generated, by bringing the rays of  light together, by
means of a lens.   There can be but little doubt, but that
the heat emitted in  such  cases, is in consequence  of the
union  of light with the  bodies, thereby depriving them
of their  capacity for heat.   Hence  we find,  that the ab-
sorption  of light is proportionate  to its intensity;  and  the
extrication of  heat is proportionate to  this  absorption.
It appears co  me  highly  probable,  that many of the sud-
den  variations  of  the  temperature  of  different  spots,
arise from variations  in  the  capacities  of  substances to
■absorb light,  and consequently give  out heat.   May  not
these  capacities be most  materially  affected, by  varia-
tions  in  the  quantities of water,  electric fluid,  growth
of plants, &c?

  The means of extricating light from bodies may be divi-
ded  into such as are mechanical, and such as are chemical.
The mechanical means are very few.  Simple pressure, in
some instances, causes the extrication  of light; as is the 
DISCOURSE  II.                 85
case, when two hard stones are struck against each other
in the dark, whereby the air is compressed, and the light
squeezed  out,  as appears by the flash following  instantly.
The electric  fluid also,  when  passing  through air,  sets
light at liberty, by  taking its  place.  This is the reason
why flashes of light follow  the  quick passages of  elec-
tricity.

  But the purest light is emitted during the combustion of
bodies.  It is, like  heat, yielded by the  air consumed, as
well as the body burnt.   When the combustion is perfect,
by the proper supply of fresh  air, the light is  in  largest
quantities. Hence the superiority of Argand's lamp, which
by admitting fresh air directly to the burning oil,  so favors
the combustion, that the oil is not  evaporated, or  lost in
the  form  of  lampblack;  but is  entirely consumed.  A
mixture of oil and phosphorus in a vial when uncorked of
nights, will give  out sufficient light for distinguishing the
figures of a watch.  The  method of preparing  this  will
be given under the head of phosphorus.

  The above facts clearly shew, that light combines with
other substances,  as .well as the following.  Light is emit-
ted in the night, from several substances which had  been
exposed to it during  the day.   Such are  called Solar phos-
phori, or substances which shine in the dark, without giving
out heat;  of which there are great varieties.  Putrid fish,
flesh,  and  rotten wood,  do it  sometimes in a very re-
markable degree;  lightning bugs,  the eyes of cats,  owls
and  several  other animals, appear  to do it  under some
circumstances.  Snow and ice seem to absorb light  all the
day, and emit it at night,  so as to prevent  total darkness.
Chemists  have made a number of  compounds, possessing
this property  in  an  eminent  degree.  Of this kind, are
Baldwin's phosphorus or nitrate of lime; Bolognian phos* 
86
DISCOURSE II.
phorus, or sulphurate of Barytes; and several' other bodies,
useless to name or describe.  Many other bodies emit light
when exposed to a high heat,  such as  diamonds,  metals,
magnesia, &c.

  The effects produced by light as a chemical agent are now
to be mentioned.  Mr. Lavoisier observes, that " organiza-
tion, sensation,  spontaneous  motion, and life, exist only
at the surface of the earth, and in places exposed to  light.
We might affirm, that the flame of  Prometheus' torch, was
the-expression of a philosophical truth, which did not es-
cape the ancients.  Without light nature was lifeless, inani-
mate and  dead.   A benevolent God, by  producing  light,
has spread  organization, sensation, and thought,  over the
surface of the earth."

  The direct influence of light on animals is very consider-
able.   In general they become unhealthy, thin, and weak,
when secluded from  light: when long  confined in a dun-
geon, a man's complexion becomes languid and dropsical.
Insects  living under ground,  and mice and other animals
confined in holes, become of a white  color.   The bellies of
fish and birds are of a light complexion ;  no doubt, in con-
sequence of their want of light.  On the other hand, it is
well known,  that animals  exposed to light,  have  their co-
lor  materially altered ;  and  it no doubt produces  other
changes : it forms one of their constituent  parts, as pro-
ved by its emission during putrefaction.

  The effects of light on vegetables are not less remarkable.
Every one knows, that several flowers follow the sun in his
course, attend him  at his evening retreat, and" by the same
law, appear before him  at his"rising.   The leaves of  many
plants change their position at different  periods of the day;
and those growing on the inner side of  windows,  seem^so- 
DISCOURSE  II.                87
Hcitous of growing towards the outside, in consequence  of
light.   It has long since been noticed,  that plants growing
in dark places are pale and  without color; and gardeners
daily avail themselves of this fact,  to furnish our tables with
white and tender vegetables.   After  the plants grow to a
certain height, they compress the leaves by tying them to-
gether, or by covering them with earth, so  as to deprive
them of light, when they  become white  soon after.   It
would probably be much better  to  cover them with tight
wooden boxes.   By such  means, they  have white  celery,
lettuce,  cabbages, endive, &c.   Red  and other  colored
roses and pinks have also been made white,  by preventing
the contact of light;  and all the plants of the kitchen gar-
dens  might be  rendered  so, by the  same means.   Grass
growing  under  stones and  other dark places, is  always
white, soft, aqueous, and of an insipid taste. The roots of
plants are also less colored, than  the parts exposed to the
sun.  Some  of  them  acquire a deleterious quality when
 suffered to grow exposed to light: as, potatoes, celery, &c.
Some plants  emit vital  air when exposed to light, and  the
more others are exposed to it, the greater is  their color,
taste and odour.  It also contributes very much to the ripen-
ing of fruit and seeds.  It  appears to  be  the  cause why,
under the scorching  sun,  near the equator, vegetables  are
 more odoriferous, of  a stronger taste,  and more abounding
 with resinous matter.   Hence the greater number  of per-
 fumes and acrid spices, which are procured from within the
 tropics.

   Lastly, light  produces  great  effects on inanimate sub-
 stances.   It causes  the decomposition of several chemical
 compounds,  and the separation  of  vital  or  pure air, in
 some instances.  These compounds will be more properly
 mentioned in another  part.  It is well known, that  the
 color of many bodies are destroyed by light.   Hence wax, 
88
DISCOURSE  II.
linen  and  cotton,  are  frequently  exposed  by house-
wives  to light, to be bleached or rendered white.   Several
considerations led me to suppose it instrumental in favoring
the  compound, which  causes  yellow fever;   these will
be  mentioned in the  next discourse,  while  treating  of
contagion.   In all  such cases,  no  doubt, sensible  light
acts  like sensible heat,  in creating the particular circum-
stances in which combinations of other matter take place
by the  exercise of their affinities.





                 ELECTRIC FLUID.
  THE various effects proceeding from electricity or light-
ning, as it is commonly called, are supposed to arise from
a fluid which  can only be  distinguished  by such effects.
This fluid, like heat, is dispersed over all nature, and has a
strong tendency to establish an equilibrium, or be equally
distributed over every body.   Notwithstanding this ten-
dency, it is  frequently accumulated  in considerable quan-
tities, by the operations of nature  and  art, as all of us know.

  The same doctrine that was delivered  concerning heat
and light, should be extended to  electricity.   We, there-
fore, must observe, that some bodies have a capacity to unite
with it, and render it  latent, from which state it may be
converted into sensible  electricity,  by  mechanical and che-
mical means.   When converted in large quantities in  the
sensible state,  it makes its escape so rapidly, as to occasion
sometimes the loudest noise,   or claps  which every one
has heard. 
DISCOURSE II.
89
   It is chiefly by mechanical means, or friction, that electri-
 city is commonly accumulated. By rubbing some substance^
 it is collected on their  surfaces in considerable quantities:
 And they are called electric bodies.  Such substances have,
 no doubt, a great capacity for electricity; and, in consequence
 of containing large quantities,  readily give a part of it up
 when rubbed.  These are  also remarkable for resisting the
 passage of the fluid ;  and  are consequently called non-con-
 ductors of electricity, to distinguish them from those favor-
 ing its escape, which are called good conductors. The most
 remarkable  of the non-conductors of electricity, are, amber,
 glass, sulphur, sealing-wax, silk, feathers, hair and wool. By
 rubbing any of these briskly on a dry woolen cloth, at night,
 the collection of the fluid may be readily  noticed, by the
 sparkles  which  take place.   The conductors of  electricity
 most remarkable, are the metals.   Of these silver, copper,
 and iron, are the best. A moist atmosphere, also, conducts
it quickly.

   In order to collect the electric fluid, an electrical machine
 is used, which, being  so common, it will be unnecessary to
 describe. The principles on which it is formed are very sim-
ple.   By  the turning of a  round non-conductor, such as a
glass cylinder, against silk,  the fluid is collected.  To pre-
vent its passage to the  earth, the machine is insulated, or
separated from the surrounding bodies, by being supported
 on non-conductors, as glass or sealing-wax.  It is necessary,
 however, that the machine  be connected to  the earth, by a
 conductor of the fluid,  as  iron  wire, for the purpose  of
conveying it from the earth to the apparatus.  When this
 machine is made on a large  scale, immense quantities of the
fluid can be collected, in dry weather, and retained some
time in glass  vessels made for the purpose.   From these it
 is applied to bodies, where  it  produces great effect*.   It
                           M 
DO
DISCOURSE  II.
 melts the hardest metals, and  decomposes  a variety of
 compounds.  In  such cases it  no doubt operates like light
 and heat, by  creating certain circumstances in which the
 affinities of particles of matter  are exercised. In its passage-
 through the air, it is characterised by the emission of light
 and heat.  These are,  in all probability,  emitted in  conse-
 quence of the fluid depriving the air of its  capacity  for la-
 tent light and heat.

   It was the great and benevolent Doctor Franklin, of this
 country, who first discovered that the lightning of the sky
 is the same as the fluid collected by the above machine from
 the earth. When it is collected in the clouds, from its ten-
 dency to establish an equilibrium,  it rapidly escapes to the
 earth, there producing the  flash of  light  and thunder.—
 The propriety of having conductors of  the fluid attached
 to houses,  to convey  it from the  clouds,  must  readily ap-
 pear. Iron rods, tipped with brass or   silver at  the points,
 are generally used.

   It is well known that the electric  fluid,  when in  consi-
 derable  quantities, destroys most  animals; yet, some of
 them, the torpedo, for example,  have the power of collect-
 ing it in great quantities, which  they emit at pleasure for
 the destruction of their enemies  and prey.

  If the doctrine I have delivered concerning electricity be
 correct; if  it unite  to  bodies  and become  latent,  as heat
and light, chemical changes in substances would naturally
produce  alterations in the capacities of bodies for  it, as
well as in their capacities for heat and light.  Accordingly
this appears to be the case in some instances, although ge-
nerally,  the escape of the fluid  cannot  be detected,  as it
flies off gradually.   Lately,  it has been found,  to the great
astonishment  of European  chemists,  that sulphur  (which 
DISCOURSE II.
91
 is electric, or contains a great quantity of electricity in a la-
 tent state) when melted with copper or iron in a Florence
 flask, from which all air is  excluded, unites to the copper,
 and appears to burn. About the bottom of the mixture, a
 sparkle appears which expands over the whole,  giving it the
 appearance of blazing. This sparkling and blaze, no doubt,
 arise from the escape of  the latent electricity of the  sul-
 phur, which is set at liberty on its chemical union with the
 metal.  The sparkling of die water of the sea, of red hot
 metals, and of some other bodies,  very probably depends
 solely on  the escape of this fluid.   It  also appears to me
 exceedingly probable, that the frequent and great collections
of sensible electricity in  the  clouds, noticed during storms,
arise from chemical changes in the air, whereby the capa-
 city of the air to retain  the latent substance is lost.  An
 union of the air with water,  and with other substances,  may
no  doubt produce  the  changes causing alterations  in  the
capacity of the atmosphere for the latent electricity.

   The progress then of  the electricity, causing thunder
 during storms, seems briefly this :  In consequence of the
great moisture of  the atmosphere near the  earth, its capa-
city for uniting to  the electric  fluid is increased.   The air,
impregnated with moisture and electricity, ascends in the
 form of clouds.  Some  chemical  changes occur in this  air,
 in consequence of which,  its capacity for heat is increased,
 and it therefore absorbs the  heat of the vapor.  Tlie vapor,
 losing its  heat, is converted  into  water, which falls in the
 form of rain,  or hail; in consequence of the loss of mois-
ture, the capacity of the air for  electricity is lost:  it is,
 therefore, converted into sensible electricity, which flies off
 to be equally distributed, and in its flight deprives the air of
 its capacity for light, and thereby causes the flash. 
92
DISCOURSE  II.
GALVANISM.
  GALVANISM, resembling in a few of its properties the
electric fluid, is one lately and accidentally discovered by
an Italian, and which is generally termed galvanism, or ani-
mal electricity.  In nature,  it exists only in a latent state ;
and it can only be made sensible, by chemical action, where-
by the capacities of bodies for it are lost.

  Galvanism  may be  collected or made sensible by a very
simple apparatus.  For this purpose, thin plates of zinc and
silver, or zinc and copper,  are to be placed alternately, one
above the other; between each of which, thin paste board,
or any other porous substance, moistened  with an acid or
any saline solution is to  be put.  When  this is done,  the
saline solution acts on  the metals, and the galvanism is pro-
portionably generated.  A pile of this kind, consisting of  30,
40 or more pieces of each  metal, excites the galvanic fluid
so strongly, that when the top and bottom pieces  are at  the
same time touched by the fingers  moistened,  a sensation
is communicated similar to  that given by electricity,  and
a luminous spark may also be produced  by it.  The ope-
ration of this fluid, in restoring drowned persons  to life;
in exciting action in dead  animals, and in effecting  the
decomposition -of some  compounds, is  very  remarkable.
When  a  metallic wire  from  the  plate at the top of the
eolumn, and another  from  that at the bottom,  are intro-
duced in a vessel containing  water,  ardent spirit, volatile
alkali, or some other  compounds,  a decomposition imme-
diately commences, and continues to go on as long as  the
apparatus excites the  galvanism.   Such  chemical  changes
are wrought upon the  same principles that those are which
take place in heat, light, and electricity. 
DISCOURSE  II.                95
   It is highly probable  that the  agent  concerned in the
 production of these phenomena, is the electric fluid some-
 what changed or modified.   This appears from the feelings
 it excites, from  the spark it emits, and  from its  passage
 being favored by the conductors and resisted by the  non-con-
 ductors of electricity.   But  there are  sufficient reasons to
 form a distinction between the two fluids.

  A number of experiments  more  curious than  useful
have been made with galvanism.  Such as wish to know
 more on the subject, can consult the treatise by Volta.
&jS?5p 
DISCOURSE  III.
  WE now are to  consider  the qualities of those  bodies
which are called confinable, as they  can be confined in our
vessels.   It is in the consideration of these,  that we learn
the particular affinities or tendencies of substances to unite
with others.  The elements, heat, light, electricity and gal-
vanism, are chiefly distinguished by  their creating particular
states, in which particular affinities of the  confinable bodies
are exercised.   These, it must be remembered,  are not the
only agents which create  states  or conditions for the exer-
cise of affinities.   Any substance present, as air or  water,
for example, may be  chiefly  instrumental,  or have great
influence in the formation of  states or conditions, for the
exercise of the affinities between any two  bodies.  An idea
of this may be formed  by adding sulphuric acid  to one iron
vessel, and water to another :  no action ensues.  But if the
sulphuric acid be mixed with the water, then particular affi-
nities are exercised, and  consequently changes take place.
This will, in other instances, be noticed;   so that some con-
finable bodies will exert no action on each other,  unless a
third one, of a particular kind be present.  Hitherto, che-
mists have stated,  that these third substances act by virtue
of a disposing affinity.   This appears  exceedingly  erroneous; 
DISCOURSE III.
95
ior it seems impossible to conceive of such an affinity.   The
substances stated to act by this disposing affinity, act on the
same principles that heat, and the other unconfinable ele-
ments do, viz. by creating states or conditions, for the exercise
of the affinities of bodies.   On  the influence of such sub-
stances is founded the distinction between decomposition in
the dry and in the humid way.  Chemists,  as before observ-
ed, have only to notice what  substance creates the  state in
which other substances exercise affinities.

   The confinable bodies  we shall first consider are,  the elas-
tic fluids, or aeriform substances.  By these bodies, is meant
those which are commonly called airs,  and very unnecessa-
rily, by chemists, gases.   An air, or a gas, may be defined, a
compressible and invisible fluid.   Our atmosphere, or the
invisible fluid which we breathe, and which surrounds the
earth, is an example of a substance existing in the aeriform
state.

   While considering heat, it was remarked that most solid
bodies, when highly heated, were in consequence of the af-
finities exercised in that state, changed from solids to fluids,
and then to airs, in which state  they generally  absorbed or
united to sensible heat. The term vapor, is  applied to such of
them as are returned to the  state of fluids in a low heat, as
water;  and the term  air, is more particularly applied when
the bodies are not restored  to fluids in any low  heat we
know.  The distinction then between vapor and air is only
relative, depending on the degree of heat in which this con-
densation takes place.

   By an air, we must therefore understand, a solid body
changed into that state, in consequence of the  exercise of
those  affinities, peculiar to .it in a certain degree of heat.
 The solid body so  changed, is called the base of the air; 
96
DISCOURSE III.
 and the airs are named according to their bases.   The pro-
 perties of the airs are found to vary with their  bases, and
 are, no doubt, much influenced by the sensible  heat and
 light to which they unite,  and  render latent in some in-
 stances in  great  quantities.   We have, for example, one
 air which will support life  and combustion, another will
 not  support either ;  one is inflammable or will burn, an-
 other is soluble in water, &c. so  that the qualities  of all
 airs vary with  their bases,  or with the solids which form
 them.

   In order  to examine the qualities  of the various  airs,
 an apparatus is necessary, which is designated by the term
pneumatic apparatus.   It is proper to give some idea of  it in
 this  place, as it was chiefly instrumental  in enabling che-
 mists to treasure up their important information concern-
 ing the airs.  A representation  of it is given in plate II, fig.
 1.   A is a trough or tub, generally about  three  feet  long,
 eighteen inches wide, and as  many long.   Two or  three
 inches below its  brim a horizontal shelf is fastened, about
 one third the width of the trough.  Through this shelf are
 several holes wider beneath  than above,   of  a  funnel
 like shape.   This trough or tub is filled with water,  suffi-
 cient to cover the shelf about an inch.   The use of this shelf
 is  to support vessels, such  as,  tumblers, jars,  and  bell-
 glasses, in which  the airs are confined.  They are first to
 be filled with  water,  and with their  open mouths down-
 wards, are to be slided over one of the holes in the shelf, as
 the glass vessel is  represented on the tub in the above plate.
 When the air is thus conveyed to  its mouth,  by  means of
 a  tube connected to another vessel, as  that represented at
 the side of the tub,  it immediately rises in the vessel,  and
 the water proportionably  sinks.   Figure 2,  of  the above
 plate is a retort, which is very generally used  in the prepa-
 ration of different airs.   It is made of glass,  iron or clay,
 to suit the operator. 
DISCOURSE  III.                97
    It may be  well, previous to experimenting, to acquire
 the habit of managing airs, in the pneumatic tub.   This
 may be done by conveying atmospheric air from one  vessel
 to  another.  Take, for example,  a large tumbler, (which
 is a very  good  substitute for a bell-glass) fill it with water,
 and with  its mouth downwards slide it over one of the ori-
 fices on the  shelf of the tub.  Take another glass, in the
 condition that  is commonly called empty, and,  on putting
 this in the water with its mouth downwards, no water will
 enter in consequence of the air that is in it.   On introdu-
 cing this  vessel underneath  the  one filled with water, and
 turning it towards aside, it  will be found, that the air will
 ascend in the upper vessel.   By these means, carefully at-
 tended to, airs  can be  readily conveyed from one vessel to
 another.   When an air is to be prepared which is soluble in
 water, it  is then necessary  to use mercury instead of wa-
 ter.   In this case, the pneumatic trough is made small,  and
 of marble.

   In ascertaining the  qualities of all  airs  it is necessary,
 that the temperature should be uniform; as  airs are  ex-
 panded  differently in  different degrees of heat, as  before
remarked.

  Of the  aeriform bodies, none claim more our attention
 than the atmospheric air  around us.  It was  hinted, while
 considering heat, that it was a compound body..   This  will
 clearly appear from the following :

  Take a  Florence flask in  the  state called empty, intro-
duce in it a burning taper, and then stop the mouth.   The
taper will  gradually irurn more dimly until it is extinguish-
 ed.   Then open the flask in water with its mouth down-
 wards, and it  will be found that the water will rise in it to
                          N 
 98               DISCOURSE III.
 supply the place of the air, which disappeared during the com-
 bustion.  The air remaining in the vessel will neither sup-
 port animal  life, or combustion; for if any animal be in-
 troduced in it, death quickly follows; or if any burning bo-
 dy be introduced, it is instantly extinguished.

   If a  vessel containing   100  parts of  atmospheric  air,
 confined over mercury be taken, and a quantity of the filings
 of iron or of lead made red hot, in a close vessel, be con-
 veyed in the above air, they will then burn, and this burn-
 ing may be  increased by the focus of a  lens.   After the
 combustion ceases,  it will be found,  that about twenty-four
 parts of the air have disappeared, so that but 76 parts remain
 in the vessel.   This air, like the above, will be found incapa-
 ble of  supporting life or combustion, and  the  metal will
 have lost its brilliancy, and  will appear rusty.  As the  base
 of this air is  found in large quantities in nitre,  it is called
 nitrogen air.

   If the metal so burnt be then introduced in a small glass
 tube, connected  to the pneumatic tub, and made red hot, it
 will part with the air to which it had united, and re-assume its
 metallic brilliancy.  If the experiments have been performed
 with the greatest accuracy and success, precisely 24  parts
 of air will come over.

  The twenty-four parts of air so obtained,  possess pro-
 perties very  different from  the  76 parts remaining in the
 first vessel.   This air will support animal life, and a burn-
 ing body introduced  in  it will burn  with great brilliancy,
and as much as it would in the original 100 parts of atmos-
pheric  air.   Some bodies,  as  sulphur, when burnt in this
air, become  acid or sour, and in consequence  it is called
oxigen air; the  word oxigen  denoting the  origin of  all
acidity. 
                  DISCOURSE III.                 99
  Now,  if the above two airs be re-combined, they will
form again 100 parts of atmospheric air.   Therefore, our
atmospheric air is a compound, formed by  the union of
two airs, possessed of different properties,  which may be
separated into 76 parts of  nitrogen air and 24 of oxigen air,
and which may be united again together.

  Before entering further into the consideration of our  at-
mosphere, in  order that its properties may be best under-
stood,  it will be  proper to give some account of the two
airs of which it is composed;  and first, of

                    OXIGEN  AIR.

  THIS is  the only air  which supports life, as animals
soon  expire  whenever it is withheld from  them.  While
breathing, this air is applied to the lungs,  where it imparts
to the  blood  heat and new qualities.   Its presence  seems
also necessary for generation, as will appear from a paper
of mine  that  will be found in the  38th number of the
Medical Repository.   In  consequence of its supporting
life it has been called vital air; but the term oxigen is better,
as it expresses one of its properties (that of causing acidity)
and answers  other purposes.  Persons should make  them-
selves  familiar with this word, as it, and its modifications,
are unavoidably  and much used.   This air  has neither
taste,  odour, or the properties of acids.  Its weight  is,  to
 atmospheric air, as 1103 to 1000.  The base of this air is
 called oxigen, which is considered as an elementary body.
 This base has never been obtained free from combination,
 and its existence is only inferred from effects it uniformly
 produces. Oxigen exists in the greatest purity in the  purest
 oxigen air:  however, in this state, it contains more  ilatent
 heat and light than any other air.  It has a strong tendency
 to unite with many other bodies, particularly in a high tem- 
100
DISCOURSE  III.
 perature.  Generally when it does unite to them, it throws
 out great quantities of heat and light, thereby producing the
 flame noticed during combustion.  Indeed it is the only sub-
 stance which, when combining with other bodies,  allows
 the disengagement of heat and light. Hence it is the only
 substance which supports combustion.  By inflammable, or
 combustible  bodies, we must therefore  understand such
 as may be oxided, or as are oxidable,  or  capable  of uniting
 to oxigen.   When such substances are heated,  they  attract
 the oxigen, and form with it a compound which not pos-
 sessing the capacity for the heat and light that  the air did,
 allow them to be emitted in the sensible state.  This  union,
 however, is not always attended by the emission of consid-
 erable quantities of heat  and light; and even in some
 instances none that is perceptible is extricated :  the product
 formed,  has the capacity,  in such  cases, to retain the heat
 and light.   We  have an  instance  in  nitre  or  saltpetre,
 which contains great quantities of oxigen, that retains its
 heat and light.   Hence,  when nitre is  mixed  with coal,
 as in  gunpowder, and fire is applied, great heat and light
 are extricated, because the oxigen unites  to  the coal and
 forms a  compound  which has not  the capacity to  retain
 them.   When combustible bodies are heated and  introdu-
 ced in pure air, they unite to oxigen with great rapidity,
 causing  a  dazzling emission  of heat and light.   Hence
 the oxidation, or combustion  of a body, is  proportionate
 to the quantity of oxigen present.  Hence the  reason why
 a given quantity of air will last only for a certain time.__
And hence the increase of weight  which  a body gains in
burning  (allowing for the loss of heat and light)  always pre-
cisely corresponds to the loss of air.  The theory of com-
bustion may be better understood by  referring to what was
said on the  subject while considering heat. 
DISCOURSE III.
101
   When oxigen unites to different bodies, compounds, pos-
 sessed of very different properties are  produced, as airs,
 fluids  and solids.  Most of the vegetable bodies  unite to
 it and  escape  in  the form  of airs.  The metallic bodies
 unite to it, and form what are commonly termed rusts, but
 which chemists more properly call oxids.   Other bodies, as
 sulphur and  phosphorus,  unite  to it and form  a class of
 compounds,  numerous and important, known by the  term
 acids, and generally possessed of  the  following remarkable
 properties:
   L. They have a  strong tendency to  unite with water.
   2. They produce the sensation of sourness  when  applied
 to the tongue.
   3. They change most  of the blue vegetable colors to
 red, by which property they may be  readily distinguished.
   4. They unite to the alkalies,  metallic oxids, and several
 earths, forming compounds called neutral salts, as nitre,
 common salt, or copperas.

   Oxigen air is generally procured for the purpose of expe-
 rimenting, by  one of the following methods :
   1. Take a quantity  of  fresh gathered leaves of plants,
put them into an inverted bell-glass filled with pump water,
and expose the  whole to the action of  the light of the  sun.
The air will then rise up tolerably pure in the glass,  as  will
 appear by the rapidity with which any  thing will burn in it.
   2. Common nitre or saltpetre contains, as before observ-
 ed, a  great deal of oxigen ; and if it be heated in a glas3
 retort,  the air will  come over pretty pure.
   3. Black oxid of manganese, sold and called by  potters
 manganese, or  the red oxid of mercury  of lead, or of any of
 the metals, if heated red hot in a retort, will give over great
 quantities of  oxigen air; and they will be restored to their
 metallic state.   In  such cases,  the first air that comes over
should be  thrown away, as it contains a  great deal of the 
102
DISCOURSE  111.
air of the vessel; and it  should be shaken over lime water
to free it of fixed air.

  The importance of oxigen in the mineral, vegetable and
animal kingdoms,  will be better understood when we con-
sider the compounds into which it enters.

                  NITROGEN  AIR.

  NITROGEN  is the name of  an elementary  substance,
which,  like oxigen, has  never been obtained  free  from
combination.   It appears to exist  in great purity in nitrogen
air. This air was formerly termed azotic air, in consequence
of its killing animals, (which other airs do also) but Chaptal
more properly  called it nitrogen,  as it exists in great quan-
tities in nitre, as before observed.  This air extinguishes
burning bodies, and destroys animals.  Its weight is, to at-
mospheric air, as 925 to 1000.   It has no sensible taste,
nor is  it absorbable by water.  It is not characterized by
 other remarkable properties.

   The methods  of  obtaining this air pure are very simple.
 It may be had by burning any body in confined atmospheric
 air, whereby the oxigen becomes separated.   Or a mixture
 of potash and  sulphur wetted into a paste, and put in con-
 fined atmospheric air, over  water, will  absorb  the oxigen
 in a day or two.  A more expeditious method is, to inclose
 lean beef in a retort with diluted  nitric acid, and on apply-
 ing  the heat of a candle, the air will come  over in great
 quantities.

   Nitrogen is  one of the most important  elementary bodies.
 Although it be not  like oxigen, useful in respiration, yet it
 forms  the chief part of animal bodies.   It enters into com-
 bination with a variety of bodies, forming useful compounds 
DISCOURSE  III.               103
 in the animal, vegetable and mineral kingdoms, which will
 be hereafter named.  At present we shall only consider its
 combinations with oxigen, and  we will return to

                ATMOSPHERIC AIR.

   OUR atmosphere is not only compounded of oxigen and
 nitrogen, but it contains a variety of other substances which
 it holds, as it were in solution.  All the bodies around us,
 which are susceptible of evaporation,  are from time to time
 united to it •, so that its impurities are sometimes exceedingly
 great.  It occasionally not only contains substances destruc-
 tive to animals immediately, but such  as  cause their death
 by taking the place of vital air.   All over the world it  is
 found blended with water and fixed air.   Its attraction for
 water is so strong that it can be had dry only,  by confining
 it over the caustic alkalies. Rather more than one hundredth
 part of it, is universally found to be fixed  air;  and in some
 parts the quantity is greater.   It may  be perfectly freed of
 this air by agitating it over lime  water, and the diminution
 of its bulk will indicate the quantity that had been present.

  In order to ascertain the proportion of  oxigen air  in our
 atmosphere, an  instrument is necessary, which  is  called
 an eudiometer.  This is a  simple glass tube, closed  at one
 end, with a regular cavity, and divided into 100 equal
 parts.  In this tube, filled with water and its mouth down-
 wards, 100 parts of the air to be examined are to be intro-
 duced.  The method then to  ascertain the quantity of ox-
igen, is differently stated by different authors,  and none of
them  are  perfectly correct.   However, the best  way is to
 introduce  a  bit of phosphorus at the end of  a wire up in
 the air, and apply fire at the side, when the phosphorus
 quickly burns,  unites to  the  oxigen,  and  the  water  in
 the eudiometer rises  in proportion to_ the loss of oxigen. 
•
 104               DISCOURSE  III.
 Next to this method appears to be the introduction of wetted
 potash and sulphur, which slowly absorb the oxigen.  Pro-
 bably the average quantity of oxigen which will be by these
 means detected in atmospheric air, is about 24  parts in
 the hundred.  Some, however, state it  to be but  22, and
 others 27.

   Our atmosphere frequently destroys animals by  contain-
ing large  quantities of substances, which,  when introdu-
ced in the lungs remain inactive and serve mechanically to
prevent the contact of vital air, as water does, when peo-
ple are drowned.   It may always be ascertained,  whether
the air of any place be so blended,  by  introducing a burn-
ing candle, attached to a stick   If  the candle, or any other
combustible matter be extinguished when introduced  in it,
or if it burn very dimly,  such airs  will certainly prove de-
structive to animals.   This,  therefore,  affords a safe crite-
rion,  by which people may judge  of the state of airs, in
all  caves,  wells, rooms, &c. before their entrance.   The
extinguishment of  the candle in such  cases, is in conse-
quence of the want of oxigen.

   Now, if it be desired to ascertain what particular air oc-
cupies the place of oxigen air,  it can be readily  done,  by
introducing a bottle filled with water,  and emptying  it in
the place,  at which  time  the  air  fills  the bottle, which
should be  corked immediately.   If  on applying a candle to
the mouth of the  bottle the  air does not blaze, it certainly
is not inflammable air. The air is then to be put over lime
 water, and if it be absorbed by the lime so as to form chalk,
the air is  certainly  fixed air.  If it be not absorbed by the
lime, it may safely be concluded that it is nitrogen  air,
 formed in consequence of some body having absorbed the
oxigen from atmospheric air.  In all these cases the airs can
be perfectly corrected, by free dilution with, or circulation 
DISCOURSE III.
105
  of atmospheric air.  When fixed air is the cause of  the
  impurity,  its removal  may  be expedited by  throwing in
 lime or lime  water.  It  is this  air which &o generally is
 found in wells, breweries, &c.

   Besides the impurities of our atmosphere from the above
 causes, it  is  frequently rendered  injurious  to animals, in
 consequence of containing substances which the chemists,
 cannot detect.  These  are the great variety  of contagions,
 or infections, which produce small pox,  measles, malignant
 or yellow fever, &c.  The  nature of these substances is
 unknown,  and  their existence is only inferred from effects
 they produce on living  animals, and particularly on men.
 The chemists have been unable to do any thing with any of
 them, except that causing yellow or malignant fever. This
 is designated by the term miasma.   It is  a compound form-
 ed during the putrefaction of animal and vegetable matter,
 in the circumstances often existing in warm countries, and
 particularly in cities.  Immense quantities of it have lately
 been generated in the United States ; and New-York, Phi-
 ladelphia,  Baltimore,  Charleston,  Savannah,  and New
 Orleans, will long bear traces of its ravages,  as well as  se-
 veral European cities;  amongst which,  Genoa,  Leghorn,
and Cadiz, have most suffered.  When this miasma is in its
strongest state, it  excites the  plague;   as we frequently
find in Egypt, and throughout Asia and  Africa.  In a less
active state, it excites the jail, hospital, and ship fevers;
also the malignant or yellow  fever, which is observed  in
the East and West  Indies,  in  the United States, and
southern parts of Europe.  In a still less active  state,  it
produces the fevers all over the world, called  billions or re-
mittent, and intermittent fevers.

  The means of correcting the airs containing  miasma, have
 long occupied the consideration of chemists.  It is only  of
                          O 
106
DISCOURSE  III.
late that successful methods of effecting this have been dis-
covered.  Experience has uniformly taiight, that it is folly
to expect any good from large fires, from flashing gunpow-
der, from smelling camphor, tobacco, or any of the vola-
tile vegetable substances; even strong common vinegar,  so
universally used, is found of little or no service.

.   Dr. Smith of London, discovered that the fumes of the
nitric acid had a happy effect in purifying infectious air, par-
ticularly that arising during the putrefaction of animal  mat-
ter.  To dis-infect rooms and  ships, the Doctor  advises
that a quantity of nitre be warmed in a glass vessel,  and an
 equal quantity of  sulphuric acid be poured on  it.   When
 this is done, the fumes of nitric acid will ascend  in the form
 of red clouds,  which quickly spreading around will  destroy
 the contagion  very effectually.   The quantity of the  arti-
 cles used in this process, should  be regulated by the quan-
 tity of air to be purified, allowing two ounces of the  mix-
 ture to a common room.   By using these fumes  in England,
 the jail,  hospital,  and  ship  fevers,  have been at  once
 arrested in their progress.   The  same happy effects follow-
 ed its use in the north of  Europe, and also in  the East  In-
 dies,  in some remarkable instances.   The advantages  re-
 sulting from this discovery were so great,  that the British
 parliament, in conformity to their liberal custom of reward-
 ing useful men, gave a considerable sum of  money to Dr.
 Smith.

    Notwithstanding the great value of the fumes of  nitric
 acid in correcting contagious airs, Guyton de Morveau, and
 some other  French  chemists,  have ascertained that  the
 fumes of the muriatic acid are superior.   These have been
 found to be particularly  successful in destroying the  miasma
 causing the yellow fever, and other epidemical diseases of
 hot countries.  In order to diffuse these fumes in  the  air, 
DISCOURSE  III.
107
 to one ounce of dried common salt should be added the
 same quantity of sulphuric acid diluted with half  as much
 water.  When this is done, very pungent fumes will ascend
 (which are the muriatic acid, gas or air) and spread around
 in sufficient  quantities to purify the air of a  large room.
 Another  preparation,  however, of this acid, is found still
 better.   About three ounces of salt, half  an ounce of the -,
 powdered manganese used by potters, two ounces of the
 sulphuric acid, and one of water, should be  mixed  toge-
 ther in a warmed glass vessel.   This being done, a most vo-
 latile air (called the oxi muriatic gas) will ascend and  com-
 pletely destroy the  contagion,  or miasma of a  large room.
 Morveau  gives a decided preference to the use of this ar-
 ticle over  all others in purifying infected places. By it,  he
 completely  corrected  the  air  of a  church in Dijon  in
 France, which was so corrupted  from putrefaction, that no
 one could enter it with  safety.  With the happiest success,
 it has lately  been  used in destroying the miasma, which
 operated so fatally in parts of Italy, France, and Spain.

   It should be observed, that more caution is necessary in
 the use of the fumes of muriatic acid than in those of the
 nitric, which  can be inhaled with safety by any one.   My
 friend and fellow graduate, Dr. Hartshorne of  Alexandria,
 made some experiments with the fumes of the muriatic
 acid; by which it appeared they  were very fatal to the life
 of mice and puppies.   Although they have been respired
 by men without injury, yet it would be well to be  cautious
 in not  remaining  too long in the room when they are es-
caping.

   These fumes, no doubt, act by uniting to  the  miasma
 thereby  rendering  it  neutral.   The expence of  prepa-
 ring them is so trifling, that they should be used in all sus-
 pected  places.  By using them in ships,  and  about  their 
108
DISCOURSE  III.
contents,  really more good will be done in one hour, than
can be produced by the longest quarantine they are made to
perform.  The benevolent President, has called the atten-
tion of Congress to this  subject  in a late message,  with
a view to remove the grievances arising from quarantine
laws.   Surely the merchants  should strive  to hasten  the
abolition of these restraints on commerce, by introducing
the perfectly safe, and expeditious method of fumigating
their ships and goods as above proposed.

  Some  persons have attributed great  virtues to slacked
lime; but with what propriety remains to be determined.
Probably  it only acts by resisting putrefaction.   However
there is a doctrine which has for its support  the  opinion of
Dr. S. L.  Mitchill, that the lime and  also the alkalies
operate by absorbing the miasma, which the Doctor calls
the sceptic acid.   At all  events  in  the  cities, where  the
privies are very offensive, the  lime thrown in, has a hap-
py  effect in correcting  the  smell  of the  air.  Perhaps
in such Cases it would be better and less expensive to  use
the fumes of the acids.   The  lime  might  be better  em-
ployed, if sprinkled over the narrow and dirty streets in
the unhealthy parts of the cities, as it could certainly cor-
rect putrefaction.

   From a variety of facts, which have  been accurately at-
tended to, it is well ascertained,  that  the activity  of
miasma is lessened,  nay,  completely destroyed,  by a  free
circulation of, or dilution with atmospheric  air.  Hence,
during the most fatal plagues  which  have prevailed in
Aleppo,  Alexandria,  and  Grand Cairo, in Egypt,  the
wealthy  people safeLy retire to the upper  stories of their
houses; where the miasma cannot ascend from the streets
without great dilution with air.  It would be advantageous
if such as are obliged to remain in  our cities, during the 
DISCOURSE  III.               109
epidemical fevers, would reside  in the upper parts of the
highest houses.  The free ventilation  of ships  and goods
coming from infected places, should also be attended to.  It
has been found,  that fresh clay has great power in absorb-
ing or destroying miasma.  Perhaps it would be best not
to pave the streets of  the cities  at  all,  or sometimes to
plough up the pavements when the contagion seems gene-
rated in great quantities.  But to conclude with this sub-
ject, I shall insert a letter which  I wrote  to Dr. Rush of
Philadelphia,  under  the impression that it  may contain an
useful hint.
               UNITED STATES NAVY-YAKD,
                         New-York,  15th June,  1806.
Dear Sir,

     YOU will,  I hope, excuse  my troubling you at this
time with suggestions concerning  the means of arresting the
progress of the fatal epidemics, annually desolating the first
cities of our country, as there is  no person to whom I can
communicate  them with more propriety than to  yourself.
For  what medical luminary has  so long acted usefully on
an extensive scale; by deviating from the practices of others;
by shewing the citizens the error  of their notions about yel*,
low fever; the folly of dealing with measures of  a  mar-
vellous kind for preservation, and the advantages of pursu-
ing natural means, for  securing natural ends ?

   Before leaving Virginia, I was firmly persuaded of the
truth of the doctrines which you taught in the university
concerning the malignant fever in this country.   That it is
a disease, the  cause of which is generated at home, and not
propagated by contagion, is so clearly true, that it is admit-
ted and supported by most of the faculty,  who do not op-
pose the doctrine solely with a view  to preserve the favora-
ble opinions of such wealthy and prejudiced persons as em- 
110
DISCOURSE III.
ploy them : and indeed the doctrine is even rapidly gaining
ground among  all the citizens.   The  general desire at this
time is,  to discover means, not for avoiding  importation,
but for preventing at home the formation of that something,
called  miasma,  and  causing yejlow or malignant fever.  In
the course of your labors,  you have strongly recommended
the removal of  all collections of vegetable and animal mat-
ter disposed to putrefy. You have considered that the mias-
ma, or cause  of the fevers, was generated during the putre-
faction of  such substances;  and you have taught that the
removal of these ; that the preserving clean the places fre-
quented by the  people, would  secure the cities against ma-
lignant fever. Unfortunately for the health of the citizens,
your advice has been but partially followed, and perhaps it
cannot strictly be put in practice :  for  it seems almost im-
possible to remove all the putrefying masses from the cities
at least while so many persons of qareless and filthy habits,
have so much of their own way.

   To  me,  it appears highly probable,  that the  continued
action  of the  light of the sun, has more influence in favor-
ing the generation of miasma,  than has hitherto been sup-
posed.   It has long been known, that in the animal and vege-
table kingdoms, it produces  most remarkable effects.  But
few persons are unacquainted with the facts, that the color of
the skins of some animals is  materially changed by exposure
to light; that by the same means, white vegetables which
have grown in the dark lose  their whiteness, and have  their
mildest juices converted into the most  active ; and that it
is in consequence of the strong light within the tropics, that
so many plants are spices and are very acrid.  Surely these
facts are more astonishing, than the production of that mias-
ma by  light which excites fevers. 
DISCOURSE III.
Ill
  No one will pretend to say that the malignancy of fevers
is proportionate to putrefaction.   It even seems likely, that
the  simple putrefaction of bodies, under common  circum-
stances, such as the existence of heat and  moisture, is not
in reality injurious to men.  In all woods, where heat and
moisture  abound, we know that putrefaction  progresses
constantly and rapidly; yet persons enjoy in them the best
health, particularly in this country.  During the unhealthy
seasons, In the southern  states,  it is  common,  in  some
places,  for gentlemen  to remove  from their towns  and
plantations into the thick woods, where they have houses
slightly built for  their  reception:  so generally is  it
known to be safe to reside in shaded places!  Lands shortly
after  they are cleared, are  also found  to be  healthy, al-
though the  putrefaction of  animals  and plants must be
immense, from the suddenness of the  alteration.  It seems
almost unquestionable that  it  is only  after  long exposure
to the rays of the sun, that such a species of putrefaction
takes place,  as   is characterized by the formation of the
very active compound, causing the fevers which have lately
proved so destructive in some parts of this country.

  The theory advanced in  my inaugural essay, of which
you were pleased to express your approbation,  led me to-
form an  idea of  the manner by which light, was directly
instrumental in  creating  miasma.  From  the  firm  con-
viction of the truth of  the position, it was without hesita-
tion that I stated  " that the form and properties of all com-
pounds were acquired in consequence of the exercise of
the chemical laws or affinities of substances, in the  state,
condition, or circumstances,  in which they were placed"—
that of course " any material change of circumstances, was
followed by a change of the properties of  the substances
placed in them,"  and that we were  to  learn by experience
what particular circumetances were necessary  to favor the
production of any particular compound." 
112
DISCOURSE  III.
   From the above considerations, I am led to conclude, that
 such is the peculiar nature of light, when it is strong and long
 continued,  that it  creates the  particular  circumstances in
 which the particles of putrefying matter  of a certain kind,
 so combine, as to form a compound which acts on men and
 excites in them malignant and yellow fevers.  Should it be
 asked, why this compound, called miasma,  continues to be
 formed in the autumn, when circumstances  are changed by
 the diminution of light—and what is partly  necessary also,
 heat;  the answer is, that such  is the constitution or nature
 of things,  that a ferment or chemical change once excited
 in any part of a mass, has a strong  tendency  to pervade
 gradually the  whole of it, as  is instanced in fermenting
 fluids, burning materials, and indeed in any body in which
 an alteration is wrought in one  part before it is in another.
 When the light has been such,  as to  create that  condition
 in which miasma is formed over any surface—an idea of it
 can  be conveved by observing that' there  is a miasmatic
 state.'—By this it will be understood that miasma exists : as
 the  circumstances  in which  miasma  is formed  cannot
 continue, without  the formation  of it—and indeed  the
 existence of the circumstances can only be ascertained by
 the  appearance  of the result,  or compound.—Now  the
 way to prevent the formation of such an active substance is
 to prevent  the existence  of the circumstances adapted for
 its formation.  Inasmuch,  therefore, as we have the power,
it should be exercised in diminishing that light—favoring the
 production of deleterious substances where people dwell.

  It might also be stated as generally true—that the activity
 of the miasma, formed during putrefaction, is proportion-
 ate to the intensity of the light in which the bodies putrefy.
Hence in countries when  the light is strongest,  as in Egypt,
the  miasma excites the plague: in the towns  of the United
States, a less violent disease, the yellow fever; and  in our
counties, only the remittent and intermittent fever? 
DISCOURSE  III.
113
   In order, therefore,  to preserve cities from the terrible
 epidemics, in addition to your wholesome advice of keep-
ing them clean, by which much disagreeable stench will be
avoided immediately, I would recommend shielding them
from the action of the sun as well as can be done. Coarse
and  strong linen made in sheets,  could easily be extended
from the eves of the houses on one side of the street, to
those of the other.  These could be so constructed, that they
might be readily removed in all boisterous weather.  The
expence and trouble would not  be comparable to that of
paving the streets, as it would require  but a little addition
to the awnings commonly over the doors  of retail stores.
But were the expence and trouble ten times as considerable,
no man of  enterprize and humanity would disgrace himself,
by putting  such considerations in competition with saving
the lives of thousands.  In a conversation on this subject,
with which I was favored, with Dr. Miller, he suggested
the  advantages of having trees of large branches, at least
in wide streets,  where they would not impede the extin-
 guishment of fires.  These certainly must prove of great
 service; not however, as formerly supposed, by absorbing
 the  miasma, but by preventing the light from favoring its
production.  Nothing  can be more certain, than that some
very good effects would be immediately produced, if  the
cities were shaded, at least in some manner more than they
now are.    The  numerous  deaths arising,  as  every one
knows, from simple exposure to the sun,  and the burning
heats created by the reflection of light from the walls, would
be avoided; while the  laborers would do much more work,
 as well as the citizens in general,feel much more comfortable.
 These advantages appear sufficient to justify the adoption of
 my  plan,  independently of the fair prospect of preventing
 yellow fever.  This prospect, however, inclines me to wish
 most ardently for the  practice; for I  believe it will prove
                           P 
114
DISCOURSE  III.
 successful.  Measures less plausible, one  would suppose,
 deserve a trial,  for the restoration  of that happy state of
 things,  when the citizens  will not annually be forced away
 from the scenes of business; or compelled  to  see such
 numbers prematurely consigned to their resting places.  To
 imitate you, in quickening sttch a restoration, is one among
 the warmest wishes of
                         Dear Sir,
                   Your friend and servant,
                              THOMAS EWELL.



   OXIGEN and nitrogen unite together in different pro-
 portions,  and form 'compounds very different from atmos-
 pheric air; as will appear from the following :

   By confining  over  mercury about four parts of oxigen
 and one of nitrogen air,  on conveying the electric fluid
 through them, the base of the two airs unite together, and
 form a  fluid,  which is  the  nitric acid commonly  called
 aqua-fortis.  This fluid is again separated into the two airs
of which it is formed in a strong heat, as was before stated.
However, the nitric acid of the shops  is not procured in this
manner.   It is generally prepared  by putting two parts  of
common nitre or  saltpetre, in a  glass retort, with rather
more than one part of sulphuric acid.  On applying mode-
rate  heat the nitric acid comes over from the nitre, in the
form of  fumes,  which are by water absorbed, constituting
the nitric acid of the shops, which should be kept in  glass
vessels tightly stopt.   The nitric acid is possessed of all the
properties of acids, which have been enumerated, in an emi-
nent degree.  When pure, it  is perfectly colorless, and its
specific gravity is then 1.554.  Exposed to the air it  emits
fumes of a white appearance, which imbibe moisture.  As 
DISCOURSE III.
115
 it contains a great quantity of oxigen, it supports the com-
 bustion of several substances.   If poured on lampblack or
 oil, it burns ;  and if on the spirit of turpentine, it blazes ra-
 pidly.   It emits heat on its union with water;  but when
 added to pounded snow or ice, very great coldness follows.
 The combinations of this acid, called nitrates, will hereafter
 be considered.

   When instead of four, you cause but three parts of oxi-
 gen to unite with one of nitrogen, then an acid is formed
 which is not so  strong as the nitric, and which is called ni-
 trous acid.  The nitrous acid may be prepared by distilling
 the nitric, which in a high heat parts with some of its oxi-
 gen.  Thjs acid differs  from the nitric in being of a yellow
 or orange color, and in emitting copious red fumes. When
 concentrated,  its  specific  gravity  is about 1.580.  When
 united to other bodies,  they are called nitrites,   which,  as
 they are not of much consequence, will not be considered.

   When  but two parts  of  oxigen are chemically united to
 one of nitrogen, then an air is formed, called  nitrous air.
 This air is generally prepared by pouring diluted nitric acid
 on wires of copper, in a glass retort, connected to the pneu-
 matic apparatus.   When  heat  is  applied, the nitric acid
 parts with half its oxigen to unite  with  the copper, and the
 nitrous  air comes over,  a colorless and  permanently elastic
 fluid, which must be kept  over  water.   This nitrous air is
incapable  of supporting life, vegetation or combustion.  Its
most remarkable property is, the facility with which it unites
 to oxigen  ; as whenever they come in contact,  they unite,
and form  the red fumes of nitric acid.   In consequence of
this property,  it was proposed .to be used in ascertaining the
 quantity  erf7 oxigen air  present in  atmospheric air;  to a
given quantity of the air in a vessel) over water, is to be .in-
 troduced nitrous air, which on uniting to the oxigen, forms 
116               DISCOURSE  III.
nitric acid, which is absorbed by the water; so that the di-
minution of bulk will be  proportionate to the quantity  of
oxigen that had been present.    But this method is found
too fallacious to be relied on.

   When about one third oxigen and two of  nitrogen are
united together, they form an  air called nitrous oxid.  This
air is prepared commonly by heating the nitrate of ammo-
nia.   It is capable  of supporting animal life and combus-
tion.  Lately it attracted great attention; but has since
been found not entitled to it from its properties.

   From what has been stated, it appears  that oxigen and
nitrogen are capable of  uniting to each other in five dif-
ferent proportions.   According to the most accurate experi-
ments the exact proportions in which they combine are thus
stated :

              *              Oxigen.          Nitrogen.
 100 parts of nitric acid contain 73 parts.......  27
     do.   of nitrous acid,      68........ . .32
     do.   of nitrous air,        56..........  44>
     do.   of nitrous oxid,      37..........  63
     do.   of atmospheric air,   24 ... .......76
OF WATER.
  AS introductory to the consideration of another species
of air, I must deliver  a few  remarks concerning  water;
a fluid universally acknowledged  to be of the utmost im-
portance in the animal, vegetable, and mineral kingdoms. 
DISCOURSE III.                11"
Every one knows, that it exists in three states in nature, in
the forms of vapor, common water, and ice.

  Whenever the degree of heat  is below 32°, water is
changed into the solid called ice.  This conversion is called
freezing.   During its freezing, it undergoes an expansion,
which has, in some instances, been found sufficient to burst
a cannon.   The expansion arises partly from the extrica-
tion  of  the air contained in the water, which appears in
bubbles, and partly from the particles of the water  being
differently arranged,  so as to occupy a larger  space.  This
new  arrangement of the particles  of  water,  is in conse-
quence  of  the exercise of its affinities or laws in a low heat.

   Water  is also made  solid in other states.   It unites  to a
variety  of  substances without diminishing their   solidity.
When poured in small quantities on fresh lime, it unites to
the lime,  and may afterwards be procured, by heating  the
lime in  close vessels.  Many bodies, when  assuming their
respective shapes, which has been called,  as  before obser-
ved, crystallization, unite to water in considerable quantities;
as for example, saltpetre, common salt, Glauber's salts,  &c.
This is called the water of crystallization.   It may be sepa-
rated by exposure to high heat.

   On increasing the  degree of heat beyond 32°, ice or solid
water,  is then changed into fluid water.   During  diis
change, a capacity is acquired to  absorb sensible  heat and
convert it into latent heat.   As was  before  observed, this
heat is  not to be considered as the cause of the fluidity.

   In this  state water acts as a powerful agent all over na-
 ture.   It gives fluidity  to innumerable substances.  It exerts
 a strong attraction for a variety of bodies,  unites  to them,
 or in other words, dissolves them.   This capacity,  or power 
118
DISCOURSE  III.
to dissolve them,  is generally  much increased when the
temperature is increased, as was noticed while considering
heat.

   In a high temperature, the water takes on the properties
of an air, generally termed steam or vapor.   During this
change, a quantity of latent heat is absorbed, as was the
case in the last instance;  and,  as  was mentioned while
considering heat.   This  conversion of  water into vapor
goes on at every temperature,  but with different degrees of
rapidity, as every  one knows.  It is very much influenced
in this change by the pressure of the atmospheric air.  Un-
der the common pressure of the air  it takes place very ra-
pidly at the degree of heat marked 212 ; and  then the water
appears in the state called boiling.  This  boiling,  however,
may be produced in a much less heat, if the pressure of
the air be  lessened; as on the mountains, or by the use of
the air-pump.   When the water is  converted into  vapor,
it undergoes a prodigious expansion, and thereby produces
the powerful effects observed in the various  steam engines.

   Water, in the state in which we commonly procure it,
holds a  great variety of substances  in solution.  In snow
and rain-water,  there  are  great quantities  of atmospheric
air, and such  is called atmospherical water.  This air is found
more or less in  all water, and gives to it an agreeable flavor.
The water of springs is called soft water; it is called hard
water,  when it contains neutral salts ; and mineral water,
when it contains large  quantities of mineral  productions.
The examination  of mineral  waters will hereafter be at-
tended to.

   In order to  free water from all  the impurities, with
which it is blended mechanically,  it should be put in a tub,
the end of which should contain a little  straw, on which 
DISCOURSE  III.
119
should be placed charcoal finely powdered, about one foot
thick. A small orifice should be made at the bottom, through
which the water as it comes down may  be drawn off for
use.   Lately it has been found, that  the most putrid and
filthy water can, by these means, be rendered perfectly
pure  and  palatable.   Now, as it can be  done so readily,
and  without  expence,  it would be well  for all those who
have hitherto been obliged to use bad water, to purify  it be-
fore  use.  Masters of vessels, particularly, ought to   keep
a tub constantly with charcoal in it,  for the purpose of pu-
rifying their water,  at least when long at sea.   It would be
instrumental, probably,  in  saving  the crews from  much
sickness.

  But,  when water is chemically combined  with   sub-
stances, as  sea-salt, saltpetre,  &c. it can only be purified
by distillation.   For this purpose,  a common still will an-
swer.   If there be a little management in the fire-places of
ships, the same heat which answers for  cooking, will an-
swer for the distillation of sufficient water, from sea-water,
for the  purposes of ships.  Lately patents have been  given
for apparatus of the kind, which  any man would suggest,
who would attend to the subject.   Water, when distilled,
is found to have a particular  taste which is disagreeable.
This  arises from the want of atmospheric air; the defect
may be  readily remedied, by agitating the water in   casks
half filled, and containing uncorrupted air.

  From observing the agency of water throughout nature,
it was considered by ancients  as  an elementary body. It
was only a few years since, that the most important disco-
very  was made, shewing  that it is  a compound.   This
has  enabled  chemists  to account for many phenomena,
which were formerly deemed  inexplicable.  That it is a
compound substance, is proved by the following 
120
DISCOURSE III.
                   EXPERIMENT.

  Introduce up near the touch-hole of a gun-barrel,  iron
wire,  or a quantity  of iron filings free from all rust.  To
the toueh-hole, attach a small tube for the  purpose of ad-
mitting water.  Properly connect  the mouth  of  the gun-
barrel, with the pneumatic tub for the  collection of  airs.
Then  let  the  body of the barrel go through  a grate,  in
which there is a sufficient fire  to make it redhot; particu-
larly that part  where the  filings  of iron are  to  be well
heated.   Then, on introducing water at the  tube in the
touch-hole,  it is converted into steam,  and decomposed,
one part uniting to the iron, the other escaping in the form
of air, and  rising  in the bell-glass.   This process being
ended, on examining the filings of iron, they will be found
to appear  rusty. If they be introduced into the gun as be-
fore,  the touch-hole stopped, and a strong heat applied,  an
air will come  over, which will be found to  be  pure oxigen
air; and,  on  examining the filings,  they will be  restored
to their metallic state.   If  100 parts of water have  been
used, there will be found 15 parts of the air first coming over,
and 85 of the oxigen air last procured.  Now, if these two
airs be mixed together, on applying heat they burn, unite
together,  and form the  100 parts of water  originally used.
This  then must prove,  most satisfactorily,  that water is a
compound, formed by the union of 85 parts of oxigen air,
and 15 parts of another  air, called  hidrogen air, which
must now be considered.

   Hidrogen is the name  applied to the base of hidrogen
air, in consequence of its being one of the constituents of
water.  This base is an elementary body, and has only been
found in a  state of combination.   It exists  in greatest pu-
rity in hidrogen air.    Hidrogen air is  the lightest  of  aU
 known bodies; it bVmg, when  pure and  dry,  13  times 
DISCOURSE  III.
121
 lighter than atmospheric air.   In consequence of this, it
 is used to raise balloons.   If, on introducing any burning
 body in this air, without alfowing the admission of oxigen,
 the body is instantly extinguished,  and also animals expire
 when put in it.  Therefore the air is incapable of support-
 ing combustion or life.  If, however,  fire be applied to the
 air,  In the presence  of Oxigen,  the air  quickly burns;
 therefore  it is inflammable,  or combustible.  In this  case
 the bases of the airs unite and form water, at the same time
 throwing out heat and light.  If a vessel be filled with this
 air,  and  kept with its mouth downwards,  on  applying
 fire, it gradually burns.  If  in an  oval tin vessel, holding
 less  than a pint, be  introduced  one part of hidrogen air,
 and two of atmospheric air,  on applying fire at a small ori-
 fice, the union between the oxigen and hidrogen is so in-
 stantaneous,  that a prodigious noise is made by the siidden
 condensation of the airs.  If one part of hidrogen and tWb
 of oxigen air be mixed together, as above, on applying heat
 the union is still more instantaneous, and the noise equal to
 that of a cannon.   In making these experiments, it Would
 be well to  have the hand holding the vessel wrapt up in a
 handkerchief.

  A number of curious experiments are frequently made
 with this air.  The artificial fire-Works exhibited occasion-
ally in the cities, are made by collecting this air in bladders,
or bags of silk varnished,  which have  tubes of different
sizes  leading  from them  in various  directions,  through
which the air is pressed out.  When it comes to the  ori-
fice,  fire is applied, the air blazes,  without  smoke,  and
continues to do so  until all  is  burnt, thereby exhibiting a
most  beautiful  and brilliant spectacle,  if judiciously
 managed.
Q 
322
DISCOURSE III.
  Hidrogen air is procured for the purposes of experiment-
ing,  always by the decomposition of water.   This is some-
times done in considerable quantities by means of the filings
of iron in a tube, as above described. But more generally the
air is collected by pouring sulphuric acid on bits of iron or
zinc, diluted with four or five times its  weight of water.
To  the vessel containing  this mixture a tube must be at-
tached,  properly connected  to  the  pneumatic  tub.   The
air will  then come over in  the  bell-glasses, rapidly, and
in quantities regulated by the quantity of the articles used.

  This air is  sometimes found pure  in  nature, and it no
doubt arises from the decomposition of water.  It issues from
some springs  and  caves, at  the mouths of which it burns
when fire is applied.  It is extricated sometimes in  mines,
and is known to miners by the term fire damp:  sometimes
it proves destructive to them.  In such cases  the air should
be burnt,  or  conveyed  off by means of pipes.   In large
marshy places, hidrogen air  is frequently extricated, and
when set on fire by the electric fluid, exhibits the singular
phenomena, called Jack with a lanthorn.   When the air
escapes  to upper regions and is  there burnt, it gives rise
to that blazing in the sky called meteors; and no doubt its
combustion, and the consequent  formation of water,  is the
cause sometimes of sudden falls of water.

  Hidrogen is one of the most important elementary
bodies.   It aids in the formation of many compot  Is,
hereafter to be considered. 
DISCOURSE  IV.
   THERE is a  substance existing in immense quantities
and diffused throughout nature which is known to chemists
by the term carbon.  It exists only in the pure state in the
diamond.   However, it is the chief substance forming plum-
bago or blacklead,  pit, stone, or mineral coal, the remains
of burnt vegetable bodies, called charcoal, and a great va-
riety of other compounds,  as will hereafter  appear.  The
peculiar  and distinguishing property  of  this elementary
substance is, that  it  unites to  oxigen,  and  forms an air,
formerly termed fixed air, but now more properly, carbonic
acid, gas or air; also to iron, thereby  converting  it into
steel or a carburet of iron.

  Carbon exists  pure, and  free from combination  in the
gem,  called  diamond.  Its properties  in  this state are
familiar to most people.   It was well known to our ances-
tors, and  is principally found on the western peninsula of
India, on the coast of Caromondal, in the  kingdoms of
Golconda and Visapour, in  the  island of Barneo, and in
the Brazils.  They are  generally found bedded in yellow 
124
DISCOURSE  IV.
ochre,  or in rocks of free-stone or quarts, and sometimes
in the beds of running waters.  When taken from the earth
they are found covered with a crust of earth and chalk.

  Diamonds are generally crystallized, and shaped as an eight
sided prism.  They appear to be formed of thin plates or la-
mina, which are split or cleft with an instrument of temper-
ed steel, by a swift blow in  a particular direction.  They are
the  hardest bodies in nature, which renders it necessary to
attack them with diamond powder.  In consequence of this,
they are used to engrave stones and cut glass.  They  take
an exquisite and lasting polish.   They have a great refrac-
tive power, and consequently uncommon lustre.   The usual
color, is a light grey, often inclining to yellow, at times lemon
color,  violet  or  black,  more seldom rose-red, and  still
more rarely green, or blue, but more generally pale brown.
The purest diamonds are  perfectly transparent, and their
specific gravity is to that of water as 3.512 to 1.000.

  Diamonds do not combine with  other bodies,  excepting
iron and oxigen ; and for  it to unite with these a most in-
tense heat is requisite.   When most intensely heated in a
close vessel with iron they unite  together and form steel,
as has been proved by Morveau.   In a high heat in the pre-
sence of oxigen air, it  burns with a sensible flame,  but
slowly,  and then forms carbonic acid.  From this it is con-
cluded that diamonds are pure crystallized carbon.

  The great Newton was  the first, who, from the refrac-
tive power of diamonds, inferred that they were combusti-
ble.  His conclusion has since been proved  to be correct
by several experiments performed by different persons.  The
Emperor Francis  I. exposed to a vehement heat, the value
of 6000 florins in diamonds and rubies ; the diamonds dis-
appeared, but the rubies remained unaltered.   The Grand 
DISCOURSE  IV.                125
Duke of Tuscany had similar experiments performed, with
the same success; and also the French chemists, Darcet,
Cadet, Lavoisier, and Guyton Morveau. Lavoisier proved,
that like all other  combustible bodies,  it burnt just in pro-
portion to the quantify of oxigen presented to it; and that
the product  was carbonic acid,  the same which is formed
from the combustion of common charcoal.   Guyton Mor-
veau, placed a diamond in  a China cup, surrounded with
oxigen air, which was confined in a proper apparatus.  He
then applied the focus of a great lens, by which most intense
heat was excited.  He first observed on the diamond a black
point at the angle  struck directly by the solar rays; after
this, it soon became completely black,  and of a coally ap-
pearance ; the instant afterwards brilliant, and as  it were
boiling points were distinctly perceived.  It now began to
diminish in  size, and in a short time,  only one fourth re-
mained ; which was  shortly after  consumed in the same
manner.   The air formed, when conveyed over lime-water
was absorbed by  it and rendered it turbid, which shewed
that it was carbonic acid.   Dr. Tennant, by heating  dia-
mons in a gold vessel, with nitre, occasioned them to burn
and form carbonic acid as above, in consequence of uniting
to the oxigen of the nitre.

   Carbon  is found in nature, united to oxigen and  other
bodies in various proportions.   Plumbago  or black lead
is carbon,  united to a little oxigen and iron.  By uniting
it to more oxigen by combustion, this substance is converted
into carbonic acid.  For  it to burn, however, it  requires
a most intense  heat; and in consequence of this, vessels
used in strong fires are very properly made of it in some
places.  The incombustible pit-coal, as it  is termed, is
nearly the same as plumbago. 
12.6
DISCOURSE  IV.
   Next to these substances, the combustible mineral coal
called  also pit,  sea, or stone-coal, contains most carbon in
a given bulk.  They contain more oxigen than plumbago,
and consequently  burn so readily, that they are generally
used for fuel.  Most commonly these coals contain a little
sulphur, iron, clay and other substances: but their combusti-
bility certainly depends chiefly on  their carbon ; as,  while
burning,  the greater part unites to oxigen, and escapes in
the form of carbonic acid air.
COMMON CHARCOAL.
  When common wood is burnt so that the air does not
circulate about it very freely there is a black substance left,
called charcoal.  The quantity of charcoal yielded by differ-
ent trees varies considerably; black ash is said to yield 25
parts of it in the hundred; guiacum 24, green ash, 20, &c.—
The charcoal commonly found is impure from several com-
binations. But from whatever wood it be procured, it may
be made pure by heating it red hot in a close vessel and al-
lowing  the airs to escape.  The charcoal so treated, has a
very strong attraction to water; is of a very black color, is
porous and capable of burning quickly,  so as to be entirely
almost converted  into carbonic acid.  It resists putrefaction
very much,  and in consequence of  this all posts which are
introduced in the earth should  be burnt or charred over,
as is now  only occasionally done.  Fresh  charcoal com-
pletely  destroys the disagreeable odour of  clothes,  when
folded up in it.   As before observed, it purifies  the most
fetid water.   When boiled with tainted  meat, it takes away
the taint entirely, and it also corrects the rancidity of but- 
DISCOURSE IV.
127
ter when melted.  When  powdered,  it is the best tooth-
powder in use, and corrects disagreeable breath in a great
degree.   It is a most excellent application to old ulcers j
it not only corrects their horrid  smell, but aids in healing
them.   I have cured an ulcer on the chin by applying  it,
which had resisted all the remedies prescribed by other phy-
sicians,  and  which was deemed cancerous.  I also admi-
nistered it to a near relation affected with  heart burn,
with success.  It has a happier effect in correcting fetid and
acrid stools than chalk, and consequently should  be taken
by those laboring under billious fevers.  When finely pow-
dered, it is used to fatten fowls, and as a manure it is also of
great value if reduced to very fine powder.
AERIAL OXID OF CARBON.
   If  charcoal be made redhot in a retort with the rust or
oxid of iron and connected with the pneumatic tub, a very
light inflammable air will come over which was erroneously
for sometime taken for hidrogen air.   This air is called
aerial oxid of carbon.
LIGHT  CARBONATED HIDROGEN AIR.
  Carbon  also unites  to  hidrogen air,  and forms an air
called  light carbonated hidrogen air.  This air may be pro-
cured by  introducing redhot charcoal underneath an  in- 
128
DISCOURSE IV.
verted  bell-glass filled   with water : the air rises to the
top,  and then to be freed of carbonic acid, should be agi-
tated over lime water.  It burns with a blue flame.  After
it is burnt, the  products are water, and carbonic  acid as
must readily appear. This air is extricated about marshes,
ditches, and putrid water.   It may  be formed by keep-
ing hidrogen  air over charcoal in the sun ; also,  by heat-
ing moistened charcoal, or sawdust in  a retort  connect-
ed with the pneumatic  tub.
HEAVY CARBONATED HIDROGEN AIR.
  Chemists  have observed  that  there  is  another kind
of air formed by the union  of carbon  and hidrogen.—
This  is called heavy carbonated hidrogen air.   It is pro-
cured by  several means: one  of which is  by  allowing
ether or alcohol  to  pass through a redhot earthen tube.
This air is inflammable, is fetid, and is most remarkable  for
being converted into an oil, when four parts of oxi-muri-
atic acid air are added to three parts of it, and agitated over
water.  It contains more carbon than the last named air.
CARBONIC ACID.
  When oxigen is fully saturated  with, or  combined to
carbon,  the well known compound  is formed, which has
been called aerial acid, fixed air, mephitic air, but more pro- 
 
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Fiy.J
Fy.
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l 4Pnetmaticyfyytamtzis or 7lf>







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J)octr. r~/P/o0tAsA/i/iaratus
Pul/ish'd lyBrvtiankBrannan ,. \ew JordJ8o6'. 
DISCOURSE IV.
129
perly carbonic acid.  According to Lavoisier this air is formed
of 28 parts carbon and 72 oxigen.   Carbonic  acid exists in
great quantities in nature, in an aeriform, and in a combi-
ned state.  It is among the heaviest airs known; its specific
gravity being to that of atmospheric air,  as  1500 to 1000,
so that it can be poured out of one vessel into another.—
This air may be collected in vessels, by emptying bottles  of
water when it  exists, in caves or  in tubs where beer  or
wine  ferments.  Or it may  be had by burning charcoal in
pure oxigen air;  or pouring sulphuric acid on  chalk, and
receiving the air as it escapes, causing the effervescence in
bladders, or in the pneumatic tub.   When it is collected it
will  be found  possessed of the following properties: it is
invisible: it extinguishes burning  bodies introduced in it,
and it is  fatal to animal life.  It exerts powerful effects on
living vegetables.  Its taste  is pungent, and in a small but
certain degree it possesses the properties  of  acids.  It pre-
cipitates lime from lime water,  by uniting to the lime, and
forming white chalk, which is insoluble.  It  is readily at-
tracted by all the alkalies.   At common temperatures it is
not acted on by any bubstance; but iron, phosphorus and
lime decompose it in a strong heat  by uniting to its oxigen.

   Carbonic  acid unites  to water, and gives it the properties
of an acid: after agitation in it, the water absorbs consider-
able quantities.  The colder the water and the greater the
pressure  applied,  the more  of  the acid will  be absorbed.
The  common  method  of impregnating water  with  it, is
through the medium of Nooth's apparatus, which is repre-
sented in plate  2, fig. 3. A is the  upper vessel, whose neck
reaches nearly to the centre  of the middle one  B, which last
is half filled with water, and has at C a glass valve which
is kept down by the pressure of the water.  At D the ma-
terials are put in; these are  generally diluted sulphuric acid 
130
DISCOURSE  IV.
and chalk, from 3 to 9 ounces of each.   This must be done
cautiously or the glass will break from the heat extricated.
The ingredients being added, the sulphuric acid unites to
the lime  contained in the chalk, which consequently gives
up  its carbonic acid.   This acid  air raises the valve at C,
passes through the water and unites to it. The water is then
drawn off at the cock E.  In this state the water is found to
possess the properties of an acid.  It sparkles  upon agita-
tion as cyder, perry,  porter, champaign, &c.  which arises
in each case in consequence of the extrication of the carbonic
acid or fixed air. Water impregnated with carbonic acid is
used as a medicine, in  affections of the stomach, kidneys,
&c. with great  advantage.  It has  also been injected in
the bowels  with the happiest effect in nervous fevers.  The
water as well as all the fermented fluids which contain this
air, may be freed of it by warming them.  A bladder attached
to the mouth of the vessels containing it, will retain the air
for  examination.

   There are but few airs more commonly met with than car-
bonic acid.  At least one hundredth part of our atmosphere
is invariably found to  be this air, and in  some places it exists
in  much larger quantities.   It is often  found occupying the
 lower parte of mines, caverns, tombs, vaults, wells, and such
 other places as contain materials for making it; and it is then
 called,   chalk damp.   The famous  grotto del Cano,  near
 Naples, has long been known,  for  the quantity  of  this
 air which it produces and which runs out at the opening,
 like a stream of water.   The quantity formed in this cavern
 is  so great, that a dog or any animal is soon killed,  if his
 nose be thrust into it.  The lake of Averno, where Virgil
 placed the entrance of hell, yields so large a quantity of this
 air, that birds cannot fly close over it with safety.  Immense
 quantities of this air are always formed  during fermentation
 and on  account of its great weight, occupies the apparently 
DISCOURSE  IV.
131
empty space, or upper part of the vessel, in which the fer.
menting process is going on.  In consequence of the extrica-
tion of this air in cellars, where beer, wine, &c. ferments, per-
sons are frequently suffocated on entering them, or in other
words are drowned in an air not respirable.  During the com-
bustion of every t pecies of wood this air is  formed in great
quantities, and being rarefied by the sensible heat, is carried
off. Sometimes however, in close rooms, it does not escape;
and falling on  the  floor it collects in such quantities as to
prove  fatal  to  those confined  in it.    To  avoid  unhappy
accidents, a  burning candle should be introduced  in the
suspected places, and if it be extinguished, as elsewhere ob-
served, the air will  not support life.  An infallible test to
determine if the air be carbonic acid is lime water, which
absorbs the air forming chalk that gives the water a turbid
appearance.  However, if a great quantity of the acid be
added to this turbid mixture, the chalk will be absorbed.

   This acid  exists in combination with a variety of bodies,
 which are called carbonates.  Every soil contains more or
 less of it.  When  a strong acid  is added to any earth, if it
 effervesce, it is in consequence of the escape of this air.
 The substances with which it is  combined must be hereaf-
 ter considered.
SULPHUR.
  THE next important elementary substance which claims
our consideration, is called sulphur, or brimstone.   It was
early known to our ancestors, and is presented by nature in. 
132
DISCOURSE IV.
a pure state   It is found in the earth, also, in various states
of combination, particularly with the metals, forming the
great variety of ores called pyrites.  About volcanoes,  it is
u.iiformly met with in great quantities, and sometimes on
the surface of waters.   It also exists in vegetable and ani-
mal substances.

   SulrJhur is universally known to be a very combustible and
brittle substance, of a pale lemon yellow  color.   Its speci-
fic gravity is 1.900.  It is destitute  of odour except when
rubbed or heated, and has a peculiar faint taste.  If a piece
of it be gently heated, as for example, by holding and
squeezing  it  firmly in  the hand, it  breaks to pieces  with
a  crackling noise.   It  is a non-conductor of  electricity,
■and hence it becomes electric by friction.  When heated, it
first softens,  then  melts at  184°, is volatilized  at 289°,
and burns at 302°.  In the beginning of  the fusion it is very
fluid, but by continuing the heat, it  grows tough and ap-
pears of  a reddish brown color.  If in this condition  it be
poured  into  water,  it remains as soft a* wax,  and this is
sometimes used  to receive impressions from seals.  Sulphur
unites with most of the earths,  all the alkalies, and most of
the metals, which last it renders brittle and fusible.   It is
soluble in oils, water takes up a  small  quantity of it, and
also ardent spirit by means of heat.  It dissolves in hidrogen
air,  forming a  most fetid air, and  unites  to phosphorus.
When heated in a close vessel it sublimes without altera-
tion ; nor is it changed by long exposure to air.

   Sulphur is procured for commerce in  prodigious quan-
tities from some volcanic countries.   Great quantities  of it
are prepared at Solfatara in Italy.  This  volcanic country
every where  exhibits marks of  the agency of subterraneous
fires ;  almost all the ground is bare and white, and is every
where  much warmer than the  atmosphere in the hotest 
DISCOURSE  IV.
133
weather.  This favors the suggestion mentioned while con-
sidering the extrication of sensible heat, that the volcanoes
arise from chemical  changes between  sulphur, iron  and
water.   The method of obtaining the sulphur for com-
merce is generally as follows.

  Pyrites  (which  is a mineral  formed by the union of a
metal and sulphur) i» broken into small  pieces,  and  put
into large  earthen tubes which are exposed to the heat of a
furnace.   A square vessel of cast iron containing water,
is connected as  a receiver to the furnace by a tube.   The
action of the fire proceeds, and the sulphur being thus melt-
ed, is gradually accumulated on  the water in the receiver.
It is then  removed from this  receiver,  and melted  in large-
iron ladles, in consequence of which its earthy parts subside
to the bottom, leaving the purified sulphur above.   When
again melted and allowed to cool gradually, it forms the
rpasses of sulphur met  with in commerce.   In order to
form this  into rolls, it is again  melted and poured into
round wooden  moulds,  the form of which  it takes,  and
in this  state they are sold  in commerce as roll sulphur.—
Flowers of sulphur as they are called, are formed by subli-
ming purified sulphur with a gentle heat in close rooms,
where the sublimed sulphur is collected, though the  arti-
cle  met  with in general under  that name is nothing but
sulphur finely powdered.

  Sulphur, like all combustible bodies, burns in proportion
to the quantity of oxigen which combines with it. It is ca-
pable of uniting to two doses of oxigen.  If melted  sulphur
be exposed to the  air while heated it takes fire,  burns with
a blue flame, and emits a suffocating vapor. This is the sul-,
phureous acid air.  It is possessed of all the properties of acids.
It is heavier than atmospheric air, and assumes a concrete
 form when made cold.   It is absorbed by water in consi- 
134
DISCOURSE  IV.
derable quantities.  It is composed of about 85 parts sul-
phur and  15 oxigen.   United to an additional quantity of
oxigen, it forms sulphuric acid. It unites to other bodies and
forms sulphites which have not been much attended to.

  When  sulphur is  fully  supplied with oxigen,  it then
forms a different and much stronger acid,  called  sulphuric
acid.  This is an article  sold in the shops commonly by the
name of oil of  vitriol, and is much employed in commerce.
It exists in immense quantities formed in nature.   Manu-
factories  for its  preparation  are established in  different
places. Usually it is thus formed:  Rooms lined with sheets
of lead are prepared, and in the bottom a small quantity of
water is  placed.   Nine parts  of  sulphur and one of nitre
are  then put in the centre and fire applied, when  the room
is closed.  The sulphur  then  unites  to the oxigen of the
nitre and forms fumes,  which run down on the walls, and
unite to  the water for which  they have strong  attraction,
then constituting the oil of vitriol of the shops, ox the sulphuric
acid, in an impure state. It is then subjected to distillation
in glass vessels. After this it is found of an oily consistence,
transparent, and possessed of all the properties  of acids
in  an  eminent degree.   When it unites to water,  much
latent heat is  set free.   The  principal use  of this acid  is
in dyeing, in which art it serves to dissolve indigo and carry
it in a state of extreme  division upon the stuffs to be dyed.
The chemist makes great use of  it in decomposing bodies.
And physicians administer it  as  a tonic in very small doses
diluted  with  water and ardent  spirit, forming the elixir
vitriol of the  shops.  It has also been used as a  manure.
Its  combinations which are of  great value, with other sub-
stances forming sulphates,  will be hereafter considered.

   As before observed, sulphur unites to hidrogen air, and
forms a very fetid air? which has some remarkable proper- 
DISCOURSE  IV.
135
ties.  This union may be effected  in s'everal ways.   The
most direct method  is,  to confine the air over sulphur, and
heat it by the focus of  a lens.   This air contains about one
eighth sulphur, and is  called sulphurated hidrogen air.   It is
an inflammable air,  and when burnt) the products are wa-
ter and sulphuric acid.  It is partially soluble in water,  to
which it gives a most nauseous taste.  It is extricated from
rotten eggs, and  is the cause of their disagreeable .smell.
It is most remarkable for reddening several vegetable colors,
in which it resembles acids.   The electric fluid when con-
veyed through it,  causes the deposition of the sulphur.

   Sulphur may be combined with the metals, by heating it
with  them.  The compounds formed are  called sulphurets,
which must hereafter be attended to. During its union with
some of them, as copper and iron, although no air be ad-
mitted, there  is  an emission of light,  as first noticed by
the Dutch chemists,  and as mentioned  while considering
electricity.  This, as before stated,  is to be attributed to
the conversion of latent into sensible electricity,  which con-
sequently escapes, throwing out the latent light of the air.
OF PHOSPHORUS.
  THERE is a  simple  elementary substance which, like
carbon and sulphur, is combustible, and by  its union with
oxigen forms an  acid.   In consequence of this I shall here
Consider its properties.   It  is  known by the term phos-
phorus. 
136
DISCOURSE IV.
   Phosphorus has never been  found pure in nature ; it is
 met with united  to  oxigen forming  phosphoric acid.   In
 that state it exists very plentifully in several animal, mineral
 andvegetable substances. When freed from its combinations,
 it is of a flesh color,  of the consistence of wax, but brittle
 in cold weather.  In atmospheric air it is luminous at com-
 mon temperatures without  emitting heat.    It has a  rough
 disagreeable taste, and its odour is like that of garlic. Its spc-'
 cific gravity is 2.033.  Exposed to the light,it becomes cover-
 ed with a crust, which is first white, next orange, and then
 red.  It becomes  liquid at a temperature of 99° and at J 22°
 it burns  rapidly, with a  brilliant white  flame, and  by
 its union with oxigen is converted  first into phosphorous
 acid. Expressed  and  essential oils take up a small quantity,
 and  also  ardent  spirit and ether.   It  combines with lime,
 sulphur and the metals.  It acts strongly and  frequently like
 poison on living animals.

  The process for obtaining pure  phosphorus usually em-
ployed is as follows:  Collect a  quantity of urine, and pour
on it a strong solution of the  nitrate of lead until it ceases
to produce cloudiness.  The mixture is then to be diluted
with water, and allowed to rest undisturbed so that the pre-
cipitate may all subside.   This being done, the clear fluid
is to be separated, and the precipitate,  which is  a phosphate
of lead, is  to be made in a paste with charcoal, and dried
gradually.   It is  then to be put in a glass vessel with  its
mouth in water, when heated, the carbon unites to the oxi-
gen of the phosphoric acid, and forms carbonic acid, which
escapes.   The  phosphorus afterwards comes over and falls
to the bottom of the water, in an impure state.   It may be
purified by a second distillation.

  Phosphorus is frequently, also, obtained from the bones of
animals.   For this purpose, the bones are burnt to white- 
DISCOURSE  IV.
137 •
ness,  and reduced to a fine powder.   After putting three
pounds of this powder in an open glass vessel,  pour on it
two pounds of strong sulphuric acid,  and gradually  add 4
or 5 pounds  of  water.  The operator must avoid inhaling
the fumes which  arise.  The whole should then be kept
gently heated for about 12 hours  more, taking care  to add
water to supply  the loss of that which evaporates.   The
next day a good deal  of water must  be added, the  clear
fluid poured off,  and the rest strained through a  cloth, and
water poured on it till it passes tasteless.   The whole of the
liquor should then be  evaporated to the consistence  of  sy-
rup in a flat earthen bason.  It is then to be mixed with an
equal  quantity of charcoal powder, distilled as above, and
the phosphorus will come over.  Phosphorus so obtained is
usually prepared into sticks or  rolls.   This can be done by
taking a long necked funnel, stopping the lower orifice,
filling it with water, and then  adding  the  phosphorus and
introducing the whole  in boiling water.  The phosphorus
melts and runs down in the neck of the funnel. The whole
is then to be removed to cold water, the stopper withdrawn,
the phosphorus  thrust out and preserved under water in
vials tightly stopt.

   The  combustibility and luminous property of phospho-
rus have given rise to  various  amusing experiments,  some
of which evince its properties very clearly.

   The names of  persons written on walls with phosphorus
have at night, for some time, a very luminous appearance,
in consequence of  the combustion.  In writing with phos-
phorus,  it is very apt  to burn briskly,  and should therefore
be inclosed in a tube,  and also be frequently introduced in
cold water.   A phosphoric fire  bottle is  prepared for travel-
lers by heating a small thin vial,  and introducing in it bits
                          s 
138
DISCOURSE IV.
 of phosphorus successively until it is filled, taking care each
 time to stop the vial after it is introduced.  Another method
 of preparing  this  bottle is,  by heating  together  equal
 parts of lime and phosphorus,  in a loosely stopped vial  for
 half  an hour.  Afterwards these vials are to be kept tightly
 stopped.   To use them, they are uncorked and a common
 match or  bit of wood  tipped with sulphur is to be intro-
 duced,  turned round, and quickly drawn out, which then
 takes fire instantly.   One part of  phosphorus and 8 parts
 of sulphur,  when  heated and  mixed  together in a vial,
 form a very inflammable compound, which when taken out
 with a  match and  rubbed  on a  cork  inflames  readily.
 When phosphorus is dissolved in  oils,  it forms what is cal-
 led liquid phosphorus.  The best method of preparing it is
 to boil gently one part  of phosphorus with six of oil of
 olives, which is to be kept well stopped, when opened at
 night it partially burns, and gives out light sufficient to show
 the hour of the night when a watch is held near.  It may
 also be used for forming luminous drawings by means of a
 brush, and it may be with safety rubbed on the hands and
 face to give them a luminous appearance at  night.  Phos-
 phorus is also soluble in  water.   If a small piece of  it be
 put in a flask with water and heated, many various appear-
 ances, resembling the aurora borealis, will follow.  This is
 in  consequence of  the  solution  of the phosphorus in the
 steam, which takes  fire  when coming in contact with the
 air as it rises.

   Phosphorus unites to a variety  of other bodies, forming
phosphurets,  which, however,  are not of great  importance.
 The one that has been most attended to is called phosphuret
 of lime.   This is formed  by the direct combination of  lime
 with  phosphorus, in a tube closed and strongly  heated.
 Phosphorus, like carbon and sulphur, unites to hidrogen air,
 and forms an air called phosphorated hidrogen air,  which is 
DISCOURSE IV.
133
remarkable for  being so combustible that it  readily burns
whenever in contact with atmospheric  air.   This  air  is
formed, by adding phosphuret of lime to water, by  which
the water is decomposed,  and its hidrogen escapes with the
phosphorus, which instantly, burns on coming to  the sur-
face.   This air is also  extricated about grave yards,  putrid
fish, &c.  It is the cause of their smelling so insupportably.

   When phosphorus unites to but a small quantity of oxi-
gen, it forms the acid called phosphorus acid, which is a vo-
latile, transparent, and dense fluid. It unites to other bodies,
forming phosphites, which have not been much attended to.

   When  phosphorus fully combines with  oxigen  it forms
the  acid  called phosphoric acid.   This acid may be formed
by the rapid combustion of phosphorus  in oxigen air;  or
by pouring on it nitric acid in a gentle heat, which parts
with its oxigen to unite with the phosphorus.  This acid is
capable of existing in a dry and crystallized state.   When
solid and placed  in contact with water it dissolves  and af-
fords a ponderous transparent fluid void of  odour.   It  u-
nites to other bodies forming compounds called phosphates,
which will be considered in their proper places.
  HAVING considered the three elementary  substances,
carbon, sulphur, and phosphorus, also, the acids they form
when combined with oxigen, it will be proper in this place
to treat  of three  acids which  are found in nature, and
which in consequence of their not having been decomposed,
are deemed elementary bodies.  They are the muriatic, the
fluoric, and boracic acids.   It is only from analogical rea-
soning  that  it  is  concluded they  owe their acidity to
oxigen. 
140               DISCOURSE IV.
              THE MURIATIC  ACID.


  THE muriatic acid exists in great abundance in nature in
combination.  United to soda, it forms common salt, which
gives the saltish taste to  sea water,  and which forms im-
mense mountains in some  places.   The acid may be had
pure by the following means in the state of an air :

  Put into a retort two parts of dry common salt (which is
properly called muriate of soda) and  gradually pour on it
one  part of strong  sulphuric  acid.  The sulphuric  acid
unites to the soda, and the muriatic acid escapes in the
form  of air,  which should be received over mercury.

   Muriatic acid air, has a remarkable  strong attraction for
water.   This is so considerable, that whenever they come
in contact, they quickly unite,  forming the muriati$  acid of
the shops,  called also spirit of  sea salt.  The air has a
very pungent and suffocating odour, which  excites  cough-
ing.   It is readily absorbed by ardent spirit, ether, fat, and
essential  oils,  melted wax, phosphorus, and  many other
bodies.  It  is possessed  of all the properties of acids.  It
 suffocates animals and is  so very caustic as to excoriate the
 skin.   It extinguishes a lighted taper, the flame of which
 becomes green, or rather  light blue, at  the  upper part.
 Light has no effect on it; heat rarefies it.   It is heavier
 than common air, its specific gravity being to that a9 1.750
 to 1.000 ; when brought in contact with oxigen air, it forms
 a white cloud.  Ice is melted by it as speedily as if thrown
 upon the fire.   It unites  to oxigen forming the oxi muriatic
 air.   It  destroys miasma.  It combines with  a variety of
 substances forming muriates, which will elsewhere be con-
 sidered. 
DISCOURSE  IV.
141
  When muriatic acid becomes combined with a  certain
quantity of oxigen, the compound is called oxi muriatic air.
Its  union, however,  with oxigen  does  not increase its
acidity.  This remarkable air may be procured as follows:

  Put into a retort one part of the black powdered  manga-
nese  which is  sold  by the potters,  and add to  it three or
four parts of the strong  muriatic acid.  Connect the retort
with  a pneumatic tub, and receive the air  over water in
the  usual manner.  When  the  air ceases  to come over,
apply the  heat  of  a lamp,  and it will come over in larger
quantities.  The air  may be  kept  in  bottles with glass
stoppers.

   This  acid may also be obtained in an indirect manner,
by decomposing muriate of soda or common salt, in contact
 with black manganese.  For this purpose, mix eight parts
 by weight of salt,  with three of the manganese,  put the
 mixture in a retort, and gradually  pour  on it diluted sul-
 phuric acid, on applying a gentle hot, the air will be libe-
 rated.   In each of the above experiments, the oxigen  is
 yielded to the  muriatic acid from the  black manganese,
 which contains much of it.

   When two parts of the nitric and one of the  muriatic
 acid  are added  together, the  nitric acid parts with its oxi-
 gen  to the muriatic,  and the oxi muriatic  acid is  formed.
 This is known by the  name aqua regia, and it  excited a
 great deal of attention in consequence of its power of dis-
 solving gold.   It is called by some  chemists  nitro-muriatic
 acid.

    The properties of this air,  are :  It possesses an  uncom-
  monly pungent and suffocating odour. It destroys miasma.
  It is very  destructive to  animal life,  particularly if not dilu- 
142
DISCOURSE  IV.
ted with common air.   It is absorbable by water and forms
with it, what is called liquid  oxi muriatic acid.   It has a
yellow  greenish color.   It is capable of maintaining and
exciting combustion in many cases.  Phosphorus, charcoal,
bismuth, iron, zinc, copper,  tin,  lead,  and  some other
combustibles take fire spontaneously when  introduced in
it  It thickens fat oils.  If yellow wax be exposed to its
action,  it is bleached.  It destroys most  vegetable colors,
or renders  them  white.   If  to a  solution of  it in water,
colored callico be  added, all the colors except the yellow
are destroyed;  in  consequence of this property of bleach-
ing, it is coming into general  use for the purpose.  When
applied either in the liquid or  aeriform  state, to thread,
cotton, linen, wax, &c.  to a very surprising degree,  and
in every season  of  the year it renders them white.  After
clothes are dipped in it, they should be washed in ley, to
destroy their bad smell.   This acid unites to other bodies
forming compounds termed oxi muriates which have excited
a little attention.
FLUORIC ACID.
  THE second acid which chemists have not been able to
decompose,  is called the fluoric.  It does not exist in large
quantities in  nature.  It is found in combinations only,
and united to lime, forming fluate of lime, or Derbyshire
spar.   It is  obtained in the state of an air as follows:

  Put one  part  of powdered fluate  of  lime into a leaden
or tin retort, and pour over it two or three parts of  strong
sulphuric acid.  A violent action instantly takes place. The
sulphuric acid unites to the lime, and the fluoric  acid rises 
DISCOURSE  IV.
US
in the form of  air.   This air is to be received over mercury
in a metallic vessel,  or in a glass  receiver lined with wax or
varnish.   A gentle heat will cause the whole of the air to
be extricated.

   The properties of this acid are: It dissolves silex, and
keeps it suspended in the aeriform state, and is consequently
used to dissolve glass, crystals, and various precious Stones.
These are, however, deposited when the air is absorbed by
water.   It is heavier  dian  atmospheric air*  It is not fit
for respiration or combustion. •  It is absorbed by water,
and forms with it liquid fluoric acid.   It has a penetrating
odour, like that of muriatic  acid air, and it corrodes animal
and vegetable  matters.   It  emits white fumes  in  contact
with moist atmospheric air.   It is very sour, and therefore
reddens blue vegetable  colors.   It unites to other bodies,
forming fluates, which  however  have not been much at-
tended to.


                  BORACIC ACID.
   THE last acid, the composition of which is unknown, is
Called the boracic. It is met with in but small quantities in
combination with soda,  forming the substance known by
the term borax.

   This  acid may be obtained pure by dissolving borax in
hot water, and  adding to  the solution gradually sulphuric
acid, till it be more than  saturated.  Then  evaporate it
slowly to one third,  and  set it aside to cool, when white
scales will be  deposited, which are boracic acid.   To be
quite pure, it  should be re-dissolved and evaporated again. 
144
DISCOURSE IV.
  This acid appears in brilliant, glittering,  white scales,-
soft and  unctuous  to the  touch.   Its taste is slightly sour
and bitter.  It is soluble in ardent spirit, which it causes
to burn,  when set on fire, with a green flame.   It is diffi-
cultly soluble  in cold water.   When  heated strongly, it
fuses into glass.   It unites to several bodies, forming borates,
which have not excited much attention.

  Besides the acids we have considered, others are procur-
ed by the combustion of metals, and some from the vege-
table kingdom, which will be treated of when considering
metallic  and vegetable substances.
*»....». 
DISCOURSE V.
  THERE are three substances, which exist in consider-
able quantities in states of combination and which are called,

                     ALKALIES.

  THEY are  remarkable  for the  following  properties:
They are incombustible, very soluble in water, and possess
an acrid, urinous taste.  They unite  to the class of bodies
called acids, and form new compounds, termed neutral salts,
in which the acid  and alkaline properties  are lost.  They
unite to oils, forming soap, which is soluble in water. They
change various vegetable blues to a green ; red to a violet
or blue; and  yellow  to brown.   Blue pigments, which
have been turned red with acids, are  restored by alkalies to
their primitive colors.   They attract  water  and carbonic
acid from the atmosphere.  They corrode animal substances,
and if very strong  convert wool into a jelly.   With these
properties, they can be readily distinguished.
                           T 
146                DISCOURSE V.
  The three alkalies are named, Ammonia, or the volatile
alkali; Potash, or the  vegetable alkali; and Soda, or the
mineral alkali, which we shall consider in the order in which
they are mentioned.




             CONCERNING AMMONIA.
   THIS alkali exists naturally in the state of air ; and wa£
first discovered by Dr. Priestley.   It has a very strong and
pungent odour.   It is lighter than atmospheric air in the
proportion of three to five.    It extinguishes  flame, yet
causes ithe  flame  of a taper to increase before  extinction.
It is unfit for respiration.   It  tinges yellow vegetable co-
lors brown, and blue ones green.  It is rapidly absorbed by
cold water, then  constituting  the spirit of hartshorn, or
sal-ammoniac, &c. of the shops.  It is also absorbed by ar-
dent spirit, essential oils, ether, charcoal and all porous sub-
stances.   When a piece of 'ice is brought in contact with
this air, it melts and absorbs it, while at the same time its
temperature is diminished.   When exposed to the tempera-
ture of 46?, it crystallizes, and when suddenly cooled down
to  68°, it assumes a gelatinous appearance, and has very
■little odour.   It unites to oils,  forming soaps,  called volatile
linaments.   When the electric spark  is  frequently run
through it,  while confined over mercury, this air is decom-
posed  into  two other airs, nitrogen  and  hidrogen :  100
parts of it,  are  separated  into SO parts of nitrogen and
20 of hidrogen, which shew, independently of other ex-
periments, that ammonia is a compound body. 
DISCOURSE V.               i47
   Ammonia may be obtained by several processes.

   The common sal-ammoniac  is formed  of the muriatic
acid and ammonia.  If to this powdered you add an equal
part of quicklime in a glass retort,  on applying a moderate
heat the ammoniacal air will come over,  and should be re-
ceived  over mercury.   The  common  hartshorn of  the
shops is a solution of ammonia in water; and by means of
heat it  may be made to part with it.  Ammonia is also af-
forded  when tin is added to the diluted nitric acid.  The
tin in this case attracts the oxigen of  the water and acid,
and the hidrogen of the water, and the nitrogen of the acid
unite,  and form ammonia.  This air is yielded during the
putrefaction of animal matter, and also when they are sub-
jected  to  the action of a high heat.  At one time the for-
mation of the volatile alkali,  during the decomposition of
matter, was considered as a proof of its animal nature; but
subsequent experience has taught that this air is afforded by
vegetables, and at  any time  when hidrogen and nitrogen
come together in due proportions.

   Ammonia  unites to  the  acids, forming neutral salts,
which  are named  according  to  the  acid  in  combination
with the alkali.  The acids with which it is most common-
ly found  in combination  are  the  carbonic  and muriatic.
forming the carbonate and muriate of ammonia. 
148               DISCOURSE  V.

           CARBONATE OF  AMMONIA.
  THIS neutral salt, is commonly called the concrete vo-
latile alkali.   It is met with in all apothecary shops.  It is
very volatile, and  is used as a medicine, in doses of  from
three to eight grains.

  This salt is prepared in several  ways.   For medicinal
purposes it may be  made by the direct combination of the
acid with the alkali; when they unite and adhere to the ves-
sel's sides.   It  may also be  prepared by introducing  chalk
well dried in a retort with sal-ammoniac, and applying heat.
The carbonic acid of the chalk then unites to the ammonia
of  the sal-ammoniac,  forming carbonate  of ammonia,
which is deposited on the sides of the vessels.  The attrac-
tion between the   acid and alkali  is, however, not very
strong; for, on adding any of the other acids, they unite
to the alkali and the carbonic acid escapes, causing an effer-
vescence.    Cold water dissolves  its own weight of this
salt.   One  hundred parts of it are found composed of 45
acid, 43 alkali, and l2of water.
MURIATE OF  AMMONIA.
  THE sal-ammoniac of the shops is a neutral salt, formed
by the union of the muriatic acid with ammonia, and is
therefore called  muriate of ammonia.   It may be formed 
DISCOURSE V.
149
by the direct combination of the acid with the alkali. Most
of the  sal-ammoniac used  in commerce is brought  from
Egypt, where it  is extracted from  soot, deposited during
the combustion of the  excrements of such animals as feed
on saline plants.   The soot  is confined in a vessel half filled
with it, and on the application of heat the sal-ammoniac is
sublimed.  The salt is prepared in other parts, by adding
common sea-salt, to a solution of the sulphate of ammoniac.
A decomposition ensues.  The sulphuric acid unites to the
soda, forming Glauber's salts, and the muriatic acid unites to
the ammonia, forming sal-ammoniac.

   Sal-ammoniac has a penetrating, acrid, urinous taste.   In
small doses, from ten to fifteen grains, it is given to excite
sweating.  It is an article much used in the arts, for solder-
ing metals, dying, bleaching, & c.  One hundred  parts of
it are composed of 52 of the acid, 40 of the alkali, and 8 of
water.

                      AMMONIA

   Also  combines  with the other acids, forming neutral
salts,  which are not of much consequence.   The most va-
luable are  the  sulphate and  the nitrate  of ammonia, which
may be prepared by the direct combination of  the constitu-
ents.  All the salts formed by the union of acids with am-
monia, receive their name  from that of  the acid and the al-
kali, as above.


              CONCERNING  POTASH.
  IF vegetable substances be burnt in the open air; if the
ashes  which remain be repeatedly washed with water, till 
150
DISCOURSE  V,
it becomes tasteless ; and if this water, which is called ley,
when  strong be then  evaporated to dryness, a substance
will remain at the bottom of the vessel,  known  in common
by the term pot or pearl  ashes.  This is potash, or the ve-
getable alkali in an impure state, in which it is used for the
purposes of commerce.  The ashes of different kinds of
wood yield different quantities of it: Those of the resinous
kind, as pine, yielding least.  Wormwood, fumitary, stalks
of beans and  corn, most  of the domestic plants, oak, birch,
and hickory trees, afford  largest quantities of it,  when burnt
to ashes.   Of the last trees, it is said to take 18001b. to form
100 of ashes, which yield not more than four or five pounds
of potash.  In the inland countries, where wood  is had in
abundance, manufactories for separating potash from ashes,
on the above principles,  are established with great advan-
tage.    This article has  been occasionally found in an un-
combined state in the earth.   In  combination with the sul-
phuric, nitric, and muriatic acids, it is frequently met with.
Chemists have not yet ascertained, whether potash be  sepa-
rated from the soil  in  which vegetables grow; whether  it
exists  uncombined  with  acids in plants  ; whether it  be  a
product of vegetation, or whether it  be generated during
the process of combustion.   At all events,  they have not
been  able  to  decompose it; and  consequently it is to be
considered as an elementary substance.

   Potash may be had in  a pure state,  by dissolving that of
the shops in boiling water, to which an equal quantity of
quick  lime is to be added.   The  solution is then to  be
poured off and  evaporated.  The substance  remaining,
should be  mixed with ardent spirit, and when  this settles,
the clear liquid  is to be  poured  off and evaporated  to
dryness in a tin or silver vessel.  The  heat  must not  be
too intense, or the potash will be evaporated also.   In this 
DISCOURSE  V.
151
state it forms the caustic alkali,  or common caustic of the
shops.

  The properties of pure potash are: It has so strong an at-
traction for water,  that it absorbs it from the atmosphere,
and thereby becomes fluid.   It dissolves all animal  parts
when brought in contact with them.   It liquifies by a gen-
tle heat, and  rises  in fumes at a high temperature.   It
unites to sulphur, forming a compound, called sulphuret of
potash, which is possessed  of some remarkable  properties.
It has a strong attraction for carbonic acid.   When fused
with  an earth called silex,  it forms glass.   It changes blue
vegetable colors green,  and finally it possesses all the pro-
perties of alkalies.                (
CARBONATE OF POTASH.
  THE  carbonic  acid  unites to  potash,  and  forms the
compound called,  generally,  mild vegetable  alkali, salt of
tartar,  salt of wormwood, &c.  but according to the new
nomenclature it is  termed carbonate of potash.   The acid
may be united to the alkali directly, by dissolving the potash
in water, and causing the carbonic acid to pass through it.
This compound was first shewn by Dr. Black to consist of
this acid and of  the alkali.  The  attraction of the potash
for the alkali is not very strong, as, on adding any of the
other acids to it they unite to the alkali,  and the carbonic
acid escapes,  causing  an effervescence.   Frequently it is
administered to patients in  this state, of parting  with the
carbonic acid, when the acid of  lemons is added, then con-
stituting what is called, the effervescing mixture.   The effer- 
152
DISCOURSE V.
vescence would be more considerable, if the alkali be fully
saturated with the carbonic  acid, which, however,  is not
generally the case.
SULPHATE  OF POTASH.
  THE acid which has the strongest affinity for potash is,
the sulphuric.   United to this, it forms the vitriolated tar-
tar of the shops, which should be called, the sulphate of pot-
ash.   It is not much used.
NITRATE OF POTASH;
             OR
   COMMON NITRE.
  POTASH is most generally found in combination with
the nitric  acid, forming the compound called nitre, or salt
petre.  It is a salt possessed of very important virtues.  It
may be formed by the direct combination of the acid  with
the alkali.   But for the purposes of commerce, it is procur-
ed from several parts of the world, where it is found blend-
ed  with the earth, particularly  in warm countries.   It is
made in considerable quantities by mixing animal and vege-
table bodies, or ashes, together with a little lime, underneath
sheds, where the water does not penetrate, but where the
air circulates freely.   A contrivance for the purpose should
be on every large estate, as it costs but little, and would be 
DISCOURSE V.                153
very profitable.  It has also been procured in considerable
quantities, from the ashes of the tobacco plant, and in ifrach
larger quantities from  grave yards, and old buildings, as in
France, Italy and Spain.

  In order to ascertain if  nitre exits in any substance,  it
should be well mixed with water,  so that the nitre may be
dissolved in it.   In this solution, bits  of paper are to be
dipt and dried,  afterwards if  any uitre  have been  in the
water, when the  paper is  burnt, it will have a particular
sparkling appearance,  which indicates the presence of the
nitre.

  When nitre is found  in  sufficient  quantities with any
earth or mixture,  to make it an object to extract it, large
tubs  are procured, in which the substances containing  it,
are mixed with water.  The water dissolves the nitre, and
the earthy parts settle at the bottom.  If any lime be present,
ashes, or potash is usually added.  The clear liquor is  then
to be poured off into  wide  mouth vessels and evaporated,
when the saltpetre will be found at the bottom in an im-
pure state.  To be freed from its impurities, it should be
again dissolved in  water and evaporated.

  It was formerly shewn, that the nitric acid is composed
of  nitrogen and oxigen, each of which exist in  our atmos-
phere.   Animal substances contain  large quantities of ni-
trogen, and  during their decomposition, this nitrogen ab-
sorbs oxigen from the air,  and forms the nitric acid.   The
nitric acid then  unites to the  potash of the vegetables, or
to lime, and forms the common nitre,  or nitrate of lime.
When the nitrate  of  lime is formed, then potash is added
to  it, which unites with the acid,  and the lime is disenga-
ged.  One hundred parts of the saltpetre, are  composed
                            u 
154
DISCOURSE  V.
of about 40 nitric acid,  50  potash, and  10 of waters o£
which last, it may be freed by heat.  From  this,  the for-
mation of nitre  about grave yards, &c. can no longer ap-
pear mysterious.

   Nitre, when  heated with  any combustible substance,
quickly accelerates its combustion, by giving up its oxigen.
Hence  a  variety of  bodies  will burn in closed vessels, if>
nitre be added.   On the facility of parting with its oxigen
is founded the use of gunpowder.  This compound is  usu-
ally formed of seventy-five  parts of nitre, nine and a half
of sulphur, and fifteen and a half of charcoal. The articles,'
 are most  intimately mixed  together in  the large  way, by
 wooden  pestles and  mortars,  which are  moved by  ma-
 chinery, turned  by water.   During the process,  the pow-
 der is  occasionally moistened, and when  it is finished, it
 is wetted still more, and pressed through small holes in skin
 sieves, which give it a granular appearance.  The powder
 is then dried and put away for common use.  When it is
 intended for particular purposes, it is usually glazed.   This
 is done  simply, by putting it  in a kind of cask, which,
 turning around, breaks off the irregular parts of  the grain,
 and polishes their surfaces.

    The excellence  of gunpowder depends  very  much on
  the  purity of the ingredients used, and the manner of  using
  them. The proportion of the ingredients varies in some ma-
  nufactories.  The charcoal commonly employed is obtained
  from the willow tree, as that is supposed to be best for the
  purpose.  Perhaps experience will teach, that  all charcoal
  is equally  good, if purified by making  it redhot in  close
  vessels, previous to using  it.  Would it not be best to free
  the nitre from its water of crystallization, by moderately
  heating it? It has uniformly been found of great consequence
  to have  the articles mixed  very minutely together; and the 
DISCOURSE  V.
155
strength of the powder is supposed to be lessened, by Wet-
ting it too much, in consequence of which, the nitre sepa?
rates from the sulphur and charcoal, and crystallizes.

  The theory to explain the  effects of gunpowder, is very
simple.  When fire is applied to it, the oxigen of the nitric
acid of the nitre, unites to the carbon and sulphur, at die
same time giving up its heat and light; by which the car-
bonic and sulphureous acids  formed, with the  nitrogen of
the nitric acid are suddenly rarefied, and by their expansion,
cause the effects noticed.
FULMINATING POWDER.
  IF to three parts of nitre, you add two of the salt of tar-
tar and one of sulphur, and reduce them to a fine powder,
a compound will be formed, possessed of more remarkable
powers  than  gunpowder.   It  is called fulminating pow-
der. If a dram of it be placed in an iron ladle, and be gra-
dually melted,  it will, when the heat is a little increased,
suddenly explode, with a noise nearly as considerable as that
of a cannon, and frequently burst the bottom of the ladle.

  Besides, for the above purposes, nitre is applied to other
uses.   It is given as a medicine to excite sweating, in doses
from 5 to 20 grains. It is used for the preparation of the
nitric acid, which is an important article of commerce ; and
it is applied, with good effects, for the preservation of flesh,
to which it gives a beautiful red color.

  All the other acids unite to potash, forming salts named'
according to the acid. These have not excited much attend 
156                DISCOURSE V.
tion.  The most remarkable is that formed by the oxi mu-
riatic acid, forming the oxi muriate of potash. This detonates
loudly  when rubbed in the mortar with  sulphur.  It has
been used for yielding oxigen air; and some have proposed
to bleach  clothes with it.


                       SODA;

                           OR

             THE MINERAL ALKALI.
  THE last alkali we have to consider, is called soda, or the
mineral alkali, which, in its properties, greatly resembles pot-
ash.  It is found in large quantities in nature. United to mu-
riatic acid, it forms salt, which gives the saltish taste to the
waters of the ocean.  It is  found united to the  carbonic,
sulphuric, and  boracic acids, in considerable quantities,
and it exists in all plants growing on the sea shore.  It ap-
pears to be deposited in large impure masses, under the
surface of  the earth, in various countries  from which  it
is extracted by running waters.  It is found after the spon-
taneous evaporation of the water, mixed with sand in the
bottom of  lakes in  Hungary, Bohemia and Switzerland,
Tripoli, Egypt, China  and  India.  It frequently oozes out
of walls, and crystallizes on their surface.

  Soda has not yet been decomposed, and in consequence,
it must be considered like potash, an elementary substance—
The method of obtaining it pure, is precisely the  same  as
that for obtaining potash.   For the numerous purposes  of
commerce, it is usually obtained from the ashes of plants,
growing on the shores of the sea. 
                   DISCOURSE  V.               157
  The properties of soda differ in no  great  degree from
potash.   It may however be distinguished from potash.—
It is rather more fusible than potash in the fire.  It has not
so strong an attraction for the acids.   Exposed to the at-
mosphere, it attracts moisture and carbonic acid, but does
not liquify like potash, but only acquires a pasty consist-
ence, and crumbles into powder.   Its evaporation in a high
heat, its great causticity, solubility, &c.  are as those of
potash.  United to oils, it  affords a solid soap, whereas,
that formed by potash and oil, is fluid  or soft.  With sili-
cious earth  it forms glass, as will hereafter be shewn.
CARBONATE OF SODA.
  THE acid with which the soda of the shops is united, is
the carbonic, forming the mild mineral alkali,  which is
more properly termed the carbonate of soda.  It  is usual-
ly procured by decomposing  plants growing on  the  sea
shore.  It is found on the surface of the earth, and on the
margin of certain lakes which become dry during  the sum-
mer.  It has often the appearance  of a rough dusty pow-
der, of  a grey color, and alkaline taste.  When pure it is
white.  This salt is chiefly used as a medicine in affections
of the kidneys, in doses from three to five grains, repeated
two or three times during the day  It would be well before
exhibiting ifto saturate it with carbonic acid by dissolving it
in water and causing a stream  of the air to pass through it. 
158               DISCOURSE V.

                  COMMON SALT *
                           OR
           MURIATE  OF  SODA.



  THE acid with which soda is found most generally unLr
ted, is the muriatic, forming  the  muriate of soda,  called
also, common salt, sea salt, and culinary salt.  This com-
pound exists in immense quantities in nature.   It is diffused
throughout the waters of the ocean.  Many mineral springs
containing it are found in various parts of  the world.  And
there are in several countries mountains and immense mines
formed entirely  of this article.  In Louisania great quan-
tities of it are found forming a mountain.   In Switzerland,
Hungary  and Tyrol it is  met with  in abundance, as well
as in Poland,  where it is  said the  richest mines  exist.
Near Cardova in Spain,  there is said to be a mountain of
common salt 500 feet high, and nearly three miles in cir-
cumference. When obtained from  the earth, it is called rock
salt.  Rock salt  is hard,  sometimes transparent, and  at
others, colored from the presence of iron.   It is dug out of
the mines, pulverised, and sold  with great advantage for
table use, in small baskets.  The  chief part, however, of1
salt used, is obtained from the water of the sea,  and is
called sea salt,  or marine salt. Sea salt is obtained from
the water containing it,  in  various  ways.

   1.  In  some  parts, the salt  sands of  the sea coast are
washed with  the  least quantity of water,  which is after-
wards evaporated.

   2.  In extremely cold countries, the salt water is allowed
to freeze, the ice is then removed,  and the remaining water
is evaporated. 
DISCOURSE  V.
159
  S. At the salt  springs in some places,  the water  is
pumped up and  suffered to fall upon heaps  of  thorns,
which divide it and cause, a part to evaporate.   The further
evaporation is carried on by boilers.

   4.  In southern countries, the extraction is begun by se-
parating a certain quantity of water from the general mass
of the sea, which is suffered to remain in square spaces and
allowed to evaporate.  In most parts,  however, the water
is put at once in large boilers, and boiled away.

   Salt has  an  agreeable, penetrating, but not bitter taste.
It is  soluble in rather less than three  times its weight of
wacer at a temperature  of 70°.  One hundred  grains  of it
are composed of 34 muriatic acid, 50  of soda, and 16 of
water, of which last it may be freed by heat.  The salt, in a
strong heat, may be evaporated entirely without decompo*
sition.

   Every one knows that large  quantities of salt, resist and
prevent the putrefaction of animal and  some vegetable
bodies.  A small quantity of it is found,  however, to in-
crease putrefaction. The manner by which it operates in
such instances is not known.

   From the great demand for soda, in the manufactories of
 soap and glass, its  price has become considerable.  In con-
 sequence of this,  it has  become  an object to  separate the
 soda from  the muriatic acid.  Various methods have been
 proposed, but they are not sufficiently economical to justify
 their adoption, on an extensive  scale. In England, however,
 Mr. Turner extracts the alkali, by means of litharge, which
 is an oxid of lead, with advantage. His method is  to mix
 the litharge widi the salt, so as to form a paste. The litharge
 gradually unites to the muriatic acid and becomes of a white 
160
DISCOURSE V.
color. The soda is then washed out with water.  Another
method is to pour the nitric acid on the salt, which unites
to the soda, forming nitrate of soda, when the muriatic
acid is disengaged. This nitrate of Soda is then mixed with
charcoal  and burnt, when  the  nitric  acid is decomposed,
leaving  the  soda  behind.
NITRATE OF SODA.
  THE nitrate of soda has also been called cubic nitre.  It
is a salt not of much value. It may be distinguished from
common nitre, by its burning on coals with a yellow flame,
whereas the flame of the other is white.
      GLAUBER'S SALTS;
                OR
SULPHATE OF  SODA.
  SODA, united to the sulphuric acid, forms the  well
known salt, called purging salts, Glauber's salts, &c. by the
common people,  but more  properly, sulphate  of soda, by
chemists  This salt may be formed by the direct combina-
tion  of the acid with the alkali: but  it is, in general, pre-
pared by pouring the sulphuric acid on common salt, and
applying a gentle heat.  The sulpTiuric  acid unites to the
soda of the  salt,  forming Glauber's  salts, or sulphate of
soda, while the muriatic acid is  disengaged in the  form-of 
DISCOURSE V.
161
air, is absorbed by Water, and is used for other purposes.
This salt is found  in  Austria, Hungary,  Switzerland  and
Siberia, always  in the neighborhood of a mineral spring.
It occurs  usually  in the state of a powder of a greyish or
yellow white appearance.

  One hundred parts of this neutral salt  are composed of
14 acid, 22 alkali, and 64 water.  When it is left exposed
to the air, it parts with this water of  crystallization,  and
appears as a white powder.  It has a bitter taste,  and one
part is soluble in two of water.  It swells up on heated coals,
and appears to  boils lrcm the dissipation of its water.   It
is used as a purgative, in doses of from one to three ounces ;
but after it has parted with its  water of crystallization, half
the quantity is sufficient.  In order to render it agreeable to
patients, it  should be dissolved in cold water with lemon
acid and brown sugar.


               PHOSPHATE OF SODA.
  SODA also unites to the phosphoric acid,  forming the
neutral salt, called phosphate of soda, which is an agreeable
cathartic, that has not  long  since been  introduced.  It is
gjven in  doses from  1 to 2 ounces, dissolved in soup.

  This  salt may be  prepared by the direct combination of
its constituent parts.  But for the shops, it is prepared by
adding the carbonate of soda to a solution of the phosphate of
lime, obtained by decomposing burnt bones with sulphuric
acid. The phosphoric acid then unites to the soda,  and is.
dissolved in the water,  while the carbonic acid unites to
the lime, forming  chalk which is insoluble.
                           x 
   DISCOURSE V.
      BORAX;
          on
BORATE OF SODA.
  SODA unites to the boracic acid, forming borax or borate
of soda, a compound which is brought from India, where
it is procured from the bottom of lakes.  Generally it is
met with in an impure state.  It  may be  purified by dis-
solving it in boiled water once or twice, then evaporating
the water.   When pure, it is white, transparent, and has
a greasy appearance when broken.   Formerly it was much
used  in  medicine,  particularly  for   children  with sore
mouths,  but at present it is much neglected.

   When borax is heated it  swells up ; the water of crys-
tallization flies off, and the salt becomes a porous, light and
opaque mass, called  calcined borax.   If this be exposed to
a strong  heat,  it is melted  into a  transparent glass, of a
greenish yellow color, and soluble in water.

   Borax is used, in several of the arts connected with the
metals. It is very generally employed  in soldering them.

   Soda unites to all  the rest of the acids, forming neutral
salts  of no  great importance.   They  are to be named  ac-
cording to the name  of the acid uniting to the alkali.


                CONCERNING  SOAP.


   IT has been stated, as one of the properties of the alka-
lies,  that they unite to oils, forming soap, an article univer-
sally  known and used. 
         DISCOURSE V.               163

     SOAP OF AMMONIA;
                on
VOLATILE  LINAMENT.
  THE volatile alkali, when fully combined with water, so
as to form the spirit of hartshorn of the shops,  is capable
of uniting to the oils, and forming a kind of soap.   The
combination may be effected, by adding the strong spirits
of hartshorn, to olive oil in an  equal quantity, and agita-
ting it very well.  This is an article chiefly used in applica
tions to joints affected with rheumatism, &c.
SOAP  OF SODA;
          OR
    HARD  SOAP.
  THE hard soap of commerce is made by the union of fat
or oil with soda.  The method of making it in the manufac-
tories is as follows:

  A quantity of the soda of  commerce, is pounded and
mixed in a wooden vessel, with about  a  fifth part of its
weight of lime,  which has been slacked  just before, and
passed through a sieve.  Upon this mixture a quantity of
water is poured, more than enough to cover it; and  in
this state it is to remain for several hours.  The lime at-
tracts  the  carbonic  acid from the  soda, and  the water
becomes strongly impregnated with the pure alkali. This
water is then  drawn off by  means  of  a stop cock, and 
16*
DISCOURSE  V.
it is called the first ley. Another quantity of water is then
to be poured on the soda, which, after  standing two or
three hours, is to be  drawn off,  and called the second ley.—
And a third portion of water is then added, and drawn off,
and called the third ley.

   A quantity of oil, equal to six times the weight of the soda
used, is  then to be put into the boiler, with a portion of the
third ley, and the mixture must be kept constantly boiling
and  agitated by means  of a  wooden instrument.  The
whole of the third and then the second ley  must be added at
intervals to the mixture.  Thq oil becomes milky, combines
with the alkali,  and  after some hours, it  begins to acquire
consistence.  A little of the first ley is then  to be  added,
not neglecting constantly to agitate the mixture.   Portions
of the first ley are to be  added at intervals ;  the soapy sub-
stance acquires gradually greater consistence,  and at last  it
begins to separate from the watery part of the  mixture.   A
quantity of  common salt is then to be added, which ren-
ders the separation much  more complete.  The boiling  is
to be  continued, still for  two hours, and then the  fire
must be withdrawn, and the liquor no longer agitated.  Af-
ter some hours rest, the soap completely separates from the
watery  part, and swims upon the surface of the liquor.  The
watery  part L  then to be  drawn off and preserved,  as  it
contains some of the soda. The fire is then to be kindled a-
gain, and a little weak ley to be added to it, to facilitate  its
melting.  As soon as it boils, the remainder of the first ley
is to be added  to it at intervals.  When the soap has been
brought to  die proper consistence, which is  judged of by
taking out small portions of it to cool, it is to be withdrawn
from the fire and the watery part separated as before.   It is
then to be heated again, and a little  water  mixed with it,
that it may form a proper paste.   After this, let it be poured
into the vessels, proper for cooling it,  in the bottom of 
DISCOURSE  V.
165
which there should be a little chalk to keep it from adhering.
In a few day- the soap will have acquired sufficient consis-
tence to be taken out and formed into cakes.

  The use of the common salt in the  above process is, to
separate the water from the soap, for salt has a stronger afhV
nity for water than soap.

  Olive oil has been found to answer best for making soap,
and next to it tallow may be placed.  Other oils have been
employed, but not  with much advantage. Whale and linseed
oil will only answer for soft  soap.

  Manufacturers have employed various means to increase
the weight of soap, without  increasing its value.  The
most  common substance used for this purpose is water,
which may be added in considerable quantities, especially to
soap made with tallow, without diminishing its consistence.
This fraud may be easily detected by exposing the soap for
sometime to the air,  when the water will evaporate and the
weight be lessened accordingly. The manufacturers to pre-
vent this evaporation, keep it in a strong solution of sea-salt.
Various other methods have also been fallen on to adulterate
soap, some of which have not been detected.

   Different chemists have analyzed soap, and it is stated to
be composed of 60 parts of oil, 10 alkali and 30 of water.
Soap made with tallow and soda has a white color and  is
therefore called white soap; but it is usual for soap makers
to lower the  price of the article,  by mixing a quantity of
resin with the tallow, which forms the  common yellow soap.
To make the soap marbled they add copperas, cinnabar, &c.
to it before it is made into cakes. 
166               DISCOURSE V.

                SOAP OF POTASH;
                          OR
                    SOFT SOAP.
  POTASH may be substituted for soda in making soap,
and the process is the same ; but the soap has always a soft
appearance ; it never being more consistent than hog's lard.
Its  properties do not differ very materially from those of
hard soap.

  Some have affirmed that they have a method  of making
hard soap with potash.   Their  method is this :  after form-
ing the soap in the manner above described, they add to it a
large quantity of common salt, boil it for some time, and
the soap becomes solid when cooled in the usual way. But
it should  be observed that the soap thus  formed contains
soda;  for when the  salt is added  (muriate of soda) the
muriatic acid unites to the potash and the soda to  the oil,
which forms hard soap.
SOAP OF WOOL.
  CHAPTAL has lately proposed to substitute  wool,  in
place of oil in the manufacture of soap. The ley is formed in
the usual manner, and made boiling hot, and threads of
woollen cloth of any kind  are gradually thrown in, where
they become soon dissolved. New portions are to be added
sparingly, and the mixture should be constantly agitated.
When no more cloth can be dissolved the soap is made. It 
DISCOURSE  V.
167
has been used in France with great success ;  and no doubt,
it would be well worth while to save all old woollen rags for
the purpose.

  The  properties of different soaps  are found to vary but
very little, although  there be great differences in the oils of
which they are formed.  They are all soluble in water and
ardent spirit;  and may very readily be decomposed by add-
ing acids to them.   They are capable of combining with a
larger quantity of oil, and rendering it  soluble in water.
Hence their property of cleansing cloths, linens, &c. When
decomposed  by a strong heat, they emit the  volatile alkali.
Several of the neutral salts, contained in the common waters,
decompose soap, and the oil rises on the surface in the form
of flakes.   Such waters are generally called  by the wash-
ing women, hard waters.

  The foam or froth which rises on pure  water, when agi-
tated with soap, is nothing more than atmospheric air, which
by the agitation is thrown in the mixture ; and which is re-
tained in it in consequence of the lktle thin coverings, or ves-
sels  of water  (vesiculx) which  continue long,  as they
are of a slimy or mucilaginous nature.

  Having spoken of soaps, formed with oils,  the present is
a proper place to mention  another kind of soap which has
been formed, by  the combination of oil  with lime.   To
form this, it is only necessary to  agitate lime water and
olive  oil together.  This  soap has been applied  to  burns,
ulcers, &c. with great advantage ; but  not for the purposes
of washing.   However, as it appears that lime has the pro-
perty of uniting to oil, to form a soap soluble in water, it is
very probable that lime water, which can readily be made
by agitating a little lime in common water, would be a very
excellent  substitute for  soap in the washing of clothes. 
168
DISCOURSE V.
The clothes might first be washed in the lime water, which
would unite to and dissolve their oil;  and then, to prevent
the lime from injuring  them, they  could be  soon after
agitated in pure water—at least, the  experiment  seems
worth trying.
^^ 
DISCOURSE  VI.
  WE come now to treat of a number of elementary bodies,
very little resembling those we have  considered.  They are
the substances forming the solid parts of the globe, which
have not been heretofore mentioned.  They are universally
known by the term minerals.   They exist in innumerable
states of combination. The art of distinguishing them from
each other, and  the method of describing them with accu-
racy and precision, is called


                  MINERALOGY.


  THOUGH there seems to be an almost infinite variety
of bodies, scattered on the surface of this globe; yet, when
they are chemically examined, we find, not without surprise,
that they are all composed of a few sample elementary
                         Y 
170
DISCOURSE  VI.
substances,  into which every one of  them can be reduced
by art.  These elements in certain properties are  found to
differ considerably from each other, which has given rise to
the distinction between earths and metals.  In this discourse
our attention will he confined to the earths,  including what
are vulgarly  called earths  and stones, which chiefly  differ
from each other in cohesion.

   The  general properties  which distinguish earths, are as
 follows :  They are incombustible and infusible.  They are
 very sparingly  soluble in water and ardent spirit.  When
 perfectly pure they assume the form of a white powder, and
 are harsh to the touch. They are capable of combining with
 acids and forming neutral salts. They are also  capable of
 uniting  with each other, and with soda and potash.  Their
 weight is less than that of metals, for their specific gravity
 never exceeds 4 : 9.

    Chemists have reduced the number of bodies, distinguish-
 ed by the above properties of earth,  to nine.  These they
 cannot further decompose ; and  therefore, they are to be
 considered  as elementary bodies.   Their names  are  as fol-
 lows :

           1 Silex,
           2 Alumine,
           3 Lime,
           4 Magnesia,
           5 Barytes,
           6 Strontites,
           7 Zircone,
           8 Glucine,
           9 Yttria. 
DISCOURSE  VI.
171
These will  be considered in the  order  in which they are
mentioned,  and only that attention will be paid to each, to
which it is entitled, by its known importance.
I. SILEX.
  SILEX, or  silicious earth, is the principal  constituent
part of a very great number  of the compound earths and
stones, forming immense masses on our globe.  It is the
basis of most of the stones which emit light when struck in
the dark,  us flint, quarts, rock crystal, jasper, Egyptian peb-
ble, &c. The sand of  the sea shore and rivers, chiefly, also,
consist of this earth.  The prodigious rocks which are dis-
tinguished by  the name of Grantie, are chiefly composed of
this earth.  All the various soils of our globe, contain it in
larger  or smaller  quantities.  It acts an  important part in
forming proper situations for vegetable bodies to grow.  It is
deposited in vegetable substances, forming petrified wood ;
and is  precipitated from the waters  of some springs.  It is
never met with in a perfectly pure state in nature.

  Silex may be obtained in a state of purity, by the follow-
ing process:  Reduce to a very fine powder four  parts of
rock crystal, and add  to  it one  part of potash.  Then melt
the whole in a strong heat.  The mass  is to be dissolved
in water,  and sulphuric acid poured on it, while a white
powder falls to the bottom.  This powder is  to be taken
out, washed  and dried, and it then constitutes pure silex.
This earth may also be had in a  state of purity, by introduc-
ing the stones containing it in the fluoric acid air. The silex 
172
DISCOURSE  VI.
is dissolved by the acid, and  when  the acid is mixed with
water, the earth falls to the bottom.

  Silex, when perfectly pure, exists in the form of a white
powder.   It is  insipid  and  inodorous.   It  is rough  to the
touch, cuts glass, and scratches, or wears away metals.   Its
specific gravity is about 2.66.  It is not altered by the com-
bustible bodies; nor does it form a cohesive mass with wa-
ter.   No acid acts upon it, excepting the fluoric.   It is un-
changed in the air.  It has been considered as insoluble in
water; but it appears, when  in a state of extreme  division,
to be soluble in ten thousand parts.  Its most remarkable,
property is, its fusing with soda and potash, in a high heat
forming the compound

                        GLASS.

   The method  of making  glass  has not long since been
brought to its  present state of perfection.   The formation
of this compound depends entirely on the chemical union
of potash or soda, with silicious earth, which takes place in
 a high temperature.   These are not employed alone in a
 state  of  purity in the glass manufactories.   The purity,
 however, of the glass, depends very much on the purity of
 those articles.   Hence the variety in the kinds of glass sold
 in the markets.

   Soda and potash are indiscriminately used in the state in
 which they  are met with in  commerce,  but soda is said to
 be preferable.   Rock crystal is employed  in a pulverised
 state when the finest  glass is to be made;  but  fine white
 sand, freed from impurities by washing, answers generally
 pretty well.  The articles are to be blended together, in
 the proportion of  one part of alkali and two of sand,  and
 in proper vessels are to be submitted to a strong heat. They 
DISCOURSE  VI.
173
 then  partially  melt,  part  with some of their impurities
 which rise on the surface, and then constitute what is called
frit.   This frit, while hot, is introduced into other vessels,
 and exposed to a strong heat  until melted, during which
 time  the impurities  arising on  the  surf ice are  to be re-
 moved.   When  the  fusion is continued for a proper time,
 the glass is allowed to cool a little,  and is then moulded ac-
 cording to the desire of the workmen.  They take a part
 of the melted matter at the end of a long hollow tube,
 which is dipped  into it, and turned about  until a sufficient
 quantity is taken up,  the workman at each turn rolling it
 gently upon a piece of iron,  to unite it  more intimately.
 The  tube is then blown through  till the melted mass at the
 extremity swells like a  bubble, after which he rolls it again
 on a smooth surface to polish it,  and repeats the blowing
 until the glass is brought to the necessary size.

    If  it  be a common bottle, the melted matter' at the end
 of the tube is put into a mould of the exact size 3nd shape
 of its body,  and the  neck is formed on  the outside, by
 drawing out the ductile glass.   If  it be a vessel with a large
 orifice,  the melted glass is  widened with an  iron tool.
 Should a handle, feet, or any thing of the kind be required,
 they are made separately, and stuck on at the melted side.
 Window glass is made in a similar way,  except that  the
 bulb at the end  of the tube is cut with shears longitudinally,
 and  is  gradually bent back until  it becomes a  flat plate.
 Large plate glass for looking glasses, &c. is made by suffer-
 ing the melted mass to flow upon  a casting table, with iron
 ledges to confine it,  and as it cools, a metallic roller is passed
 over it to reduce it  to an uniform thickness.

    The principal  kinds  of glass  manufactured  are called
 flint glass, crown glass and  bottle glass. 
174
DISCOURSE  VI.
   Flint glass is the densest, most transparent, colorless and
 beautiful:  in consequence of  which  it is called  crystal.
 The best kind is said to be made of 120 parts of pure white
 sand, 40 parts, pearl-ash, 35 red oxid of lead, 13 of common
 nitre, and  25 of black manganese. This is the most fusible
 glass. It is used for the best utensils and  ornamental pur-
 poses.

   Crown glass differs from the above in containing no lead.
 It is made of soda and fine  sand, and  is  used for panes of
 windows,  &c.

   Bottle glass is the coarsest of all, is least fusible,  and
 is made of  soda  and  common sand.  Its  green  color is
 owing to iron.

   Glass is often colored by mixing with it,  while in a fluid
 state, various metallic oxides.   It is colored blue,  by the
 oxid of cobalt; red, by  the  oxid  of gold ;  green,  by the
 oxid of copper or iron ; yellow by the oxid of silver or an-
 timony and violet by the oxid of  manganese.

   The  properties of  glass are  well known.  Its  specific
 gravity varies from 2, 3, to 4, according to  the  quantity of
 metal mixed  with it.   Though brittle when cold, it is  one
 of the most  ductile bodies known,  it  being practicable to
 draw it out in the finest threads.   It  is one of the most
 elastic and sonorous bodies.   Fluoric acid dissolves it at
 common temperatures, and soda and potash at high tem-
 peratures.

   Glass utensils, unless very small and thin, require to be
gradually cooled in an oven.  This operation is called anneal-
ing, and is indispensably necessary to prevent their crackings
by change of  temperature, or rough usage. 
                   DISCOURSE  VI.               175

                    II. ALUMINE.



  THIS earth  derives its  name  from alum, of which it
forms the base.   It constitutes the lower  parts of moun-
tains and plains.   All the varieties of  clay, owe their pro-
perties to this  earth.   It  is  met  with in various  states of
combination, with silicious earth,  carbonic  and sulphuric
acids ; united to a small portion of silicious earth, it forms
a bed for the growth  of most of the vegetable bodies.  It
is the constituent part of  many rocks.

  It enters into  composition  with all those stones called
argillaceous,  as  potter's clay,  fuller's earth,  mica,  adaman-
tine spar, noted for  its great hardness, slates, &c.  From
this it must at once appear a very important earth.

  Alumine may be  obtained tolerably pure  by dissolving
alum in five or six times  its  weight of boiling water, and
then adding to it the liquid ammonia of the shops, so long
as a white  powder is precipitated.  This white powder is
to have the fluid poured  off from it, and then repeatedly
washed,  and finally dried.

  The properties of pure alumine  are as follows : it is in-
sipid, adheres to  the tongue and occasions  the sensation of
dryness in the mouth.  When moistened with water it forms
a soft  paste.   When heated  to redness it shrinks consider-
ably in bulk, and at  last becomes  so  hard as to strike fire
with flint.  After being heated,  it is no longer capable of
forming with water a paste ;  this property,  however, it re-
covers by solution in  an acid and precipitation.  It posses-
ses a powerful attraction for lime.  The most intense heats
cannot melt it, except when united with lime and then it is 
176
DISCOURSE VI.
very fusible.   It unites strongly to  all the acids, forming
neutral  salts.  Its specific gravity  is 2.   It absorbs car-
bonic acid  and  water  from the atmosphere.   Its attrac-
tion  for  water is  so strong,  that  a lump of  it  in  the
common state,  in  which it contains much of  this fluid,
will unite to more than twice its weight of it, without al-
lowing any to drop out.  In a freezing  cold  it contracts
much and parts  with its water, which appears in the form
of frost. Hence the frequency of frost in clay soils.  Hence
the reason why such soils yield large quantities of water for
plants.   When this earth is exposed to heat, it contracts in
proportion to the degree of heat, which arises from its  loss
of water.   It is in consequence of this  that Mr. Wedge-
wood's  thermometer indicates the degree of heat,  as  be-.
fore observed.   This earth is much employed in  the arts.

   It has been observed that alumine unites to the acids, and
forms neutral salts.  These salts are to be named according
to the name of the acid uniting to the alumine.   They may
be formed by the direct combination  of the acids with the
earth.   They have not excited  much attention, excepting
only that formed by the combination of the sulphuric acid
with the earth.  This is in common language called

                        ALUM,

But in  consequence of its composition it is termed by the
chemists, sulphate of  alumine.   This neutral salt  is well
known  among artists.  It may be formed by  the  direct
combination of the  sulphuric  acid  with the   aluminous
earth.   But it is  generally prepared  for  the purposes of
commerce,  from a combination of suiphur  and alumine,
which is found in different parts.  This compound  is heat-
ed in  a moist  air,  when the  sulphur  unites  to  oxigen
forming the sulphuric  acid, which unites to the alumine 
                   DISCOURSE VI.                177

forming  sulphate  of alumine  or alum.   Water is  then
to be poured over  the  mixture,  which dissolves the alum
and carries  it  off.  This  fluid is then to  be evaporated,
after a little potash or urine, containing ammonia is added
to hasten the  crystallization, which then takes place in
large  transparent  masses.   Its taste is rather sweet,  and
very astringent.  It contains a good deal of water of crys-
tallization, of which it  may be  freed  by heating it.  It
then constitutes  what  is  called burnt  alum,  which is
sometimes applied  to sores.   Alum is soluble  in two parts
of boiling and 15 of cold water.   It is used as a medicine
in small  doses,  and is particularly  useful in  sores of the
mouth and throat.   It is very extensively used in the arts.
STONE WARE.
   POTTERY or stone ware of all sorts, from the coarsest
brown pitcher to the finest porcelain,  is made of  aluminous
and silicious earths. The use of the silex is to give strength
to the ware,  so that it may preserve its solidity during bak-
ing.   When good ware is to be made, care is taken only
to employ the fine parts of the alumine and chert, which is
a species of  flint.  With  this view  the  alumine is well
mixed  in water, by  which the  fine parts are  suspend-
ed in  the  fluid, while  the coarse  subside to  the bot-
tom.   The thick liquid  is  further purified by passing it
through  sieves.   After this the liquid is  mixed in various
proportions  for different wares, with another liquor of a-
bout the same consistence, consisting of finely ground flints.
The mixture is then dried in a  kiln, and after being beaten
                            z 
178
DISCOURSE VI.
to a proper consistence, it becomes fit for being formed at
the wheel into dishes, plates, bowls, &c.  When  t^e ware
has been exposed to heat for a certain time it is glazed,  or
is made  to undergo  a  partial  vitrification at the  surface,
without which water would pass through it.  Common pot-
tery is glazed with an oxid of lead, or  by throwing com-
mon salt over it in the furnace.

   The yellow or queen's ware  is made of the same sub-
stances as the common flint ware, but in  different propor-
tions.  The glazing is  also different. It is made by mixing
together in water,  to a consistence of cream, 112 parts of
lead, 24  ground flint, and 6 of flint glass.   The ware, be-
fore it is glazed,  is baked in the fire ;  by which it acquires
 the property of  strongly imbibing moisture.   It is in this
state, quickly to be,dipped in the composition and taken out,
when it is exposed a second time to the fire, in consequence
of which, the glaze it imbibed is melted, and a thin gloss is
formed on its surface, which is more or  less yellow, accord-
ing to the  greater or lesser proportion of lead used.

   Porcelain or china,  is a semi-vitrified earthen ware of an
intermediate  nature between common wares and  glass.
Chinese porcelain is said to be composed of two ingredients,
 one of which is a hard stone, called petunze, which is care-
fully ground to a fine powder; and the  other, called kaolin,
 is a white  earthy substance, which they  intimately mix with
the ground stone.
BRICKS.
   THE manufacture of bricks and tyles is a species of this
art.  To make good articles of this kind, the clay should be 
DISCOURSE  VI.
179
 dug out of the earth; exposed for some time to the action of
 the  air, and then powdered and made into a paste with wa-
 ter.   This paste is to be pressed in moulds; taken out and
 dried in the sun, and then burnt in  a large kiln made for the
 purpose. This kiln had best be lined with a mortar of char-
 coal and clay, which will retain the heat to act on the con-
 tents of the kiln.

  The qualities of bricks, &c. depend on the nature of the
clay  used and  the intensity of .he  heat to which they have
 been exposed. Common clays are composed chiefly of silex
 and  alumine in  various  proportions.  When the alumine
abounds, the brick contracts much  and is apt to crack while
burning.   This inconvenience is remedied by adding  sand
to the clay.  It has been found that a litde lime will render
the bricks more fusible ;  and  for  the purpose of favoring
their vitrification, it is sometimes used with advantage.  It
is the oxid of iron which gives to the bricks their color.

  As lime disposes clay to fuse or melt, it is  necessary to
avoid using it in the construction of vessels exposed to  high
heats.
III. LIME.
  THIS earth i* commonly known by the term calcareous
earth.   It is found in immense quantities in nature, though
never in a pure state.  It is always combined with an acid.
With the carbonic acid it forms chalk, common lime-stone,
marble, calcareous spar, &c.  It is contained  in the waters
of the ocean ;  it is found in vegetables, and it  is the basis of
the bones, shells, and other hard parts of animals.  Its com- 
180
DISCOURSE VI.
bination with the sulphuric acid, forms sulphate of lime or
gypsum, or  plaster of Paris.  United to the  fluoric acid it
constitutes fluate of lime, or Derbyshire spar.

   Lime may be obtained in a pure state from good chalk,
marble, or oyster shell  powder.  For  this purpose nothing
more is necessary than to expose it to a high heat in a fur-
nace, when it parts with its carbonic acid, and the lime re-
mains pure.   It is on the same principle, that lime-stone,
shells, &c. are burnt in common: they part with carbonic
acid in the high heat, and the lime consequently is left pure.
In some instances, the limestone contains impurities, parti-
cularly  silex which cause it to melt in the kilns; and this is
 called  over burnt lime.

   When lime is pure, its properties are as follow: It exists
in a solid mass of a white color, moderately hard, but easily
reducible to powder.  Its taste is bitter, urinous  and burn-
ing.  It changes blue cabbage juice to a green :  it cannot
be fused  alone in furnaces;  it  crumbles into powder in
the  air;  loses  its  strong taste, absorbs  water, and is
increased in bulk. Its  specific  gravity is 2,  3.  Its slack-
ing  by water  is attended  by the extrication  of  heat; by
hissing, splitting and swelling up, while the water is part-
ly  consolidated and  partly converted into vapor, and the
lime is  reduced to a dry powder.  It acts as a caustic on ani-
mal matter. It unites to all the  acids forming compounds
possessed of various  properties,  which are named accord-
ing to the name of the  acids. It is soluble in 300 times it6
weight of water.

   The  lime water of the shops is nothing but lime dissolv-
ed in water.  To make it, nothing more is necessary than to
add a handful of slacked lime to hot water, and agitate the
 mixture.   In  an hour or so, it is fit  for use, and  it may be 
DISCOURSE VI.
181
poured off in bottles which are tightly stopt. This article is
used by physicians, in cases of indigestion; by chemists, to
detect the presence of several substances, and by artists to
make good mortar.


                       CHALK;
                          OR
              CARBONATE OF LIME.
   IF lime water be left uncovered, a white crust forms at
the top. This is common chalk, which is insoluble in water.
It is  formed in consequence of the union of the carbonic
acid  of the air with the lime, and in the new nomenclature
it is consequently termed the carbonate of lime.  The attrac-
tion  between the acid  and the earth is, however, so incon-
siderable, that on applying any of the  acids of the shops,
they unite to the earth, and the carbonic acid is disengaged,
so as to cause an effervescence.

   Chalk, or carbonate of lime, exists in immense quanti-
ties in nature ; no other mineral can be compared with it in
the abundance with  which it  is  scattered  over the earth.
Many mountains consist of it  entirely, and hardly a coun-
try is to be found on the face  of  the  globe, where it  does
not constitute a  greater or lesser  part of the riches of the
mineral  kingdom.  But,  perhaps,  it  is seldom  or never
found in an entirely pure  state.  The variety of substances
with which it is occasionally found united,  has given rise to
several distinctions, which are grounded on appearances;
 of these it will be necessary to notice the most remarkable.

   Common white chalk  is found mixed with  saline  sub-
 stances, iron and stones of different kinds.  It may be freed 
182
DISCOURSE VI.
of most of its  impurities,  by powdering  and  washing it
very well.  The soluble parts are carried off by  the water,
and the chalk remains behind.   When  this is  made into
little lumps,  it is called prepared chalk.   It is much used in
medicine in large doses, particularly in billious fevers.

  Calcareous spar,  formed in the tops of caverns, and de-
posited from the water passing  through  them, is a combi-
nation of lime and carbonic acid, with a little water, which
enters into its composition.  The  various  kinds of marble
have  nearly the same ingredients.   This is found in  im-
mense quantities  in the earth in various  places.   It differs
in density, hardness, weight and color, and from the close-
ness of its texture, it can receive a very fine polish.  White
marble is almost a pure carbonate of lime.  The other kinds
contain silex, alumine, and iron ; to which last, they  fre-
quently owe their color.   By insensible  gradations, marble
passes into lime stone ; which is of a coarser  texture, is
more brittle,  has  less lustre,  and contains  greater  impuri-
ties.   Marl is  the last variety of this earth  which  I shall
name.  It exists in the  form of a yellowish grey  mass,
crumbles on exposure to air, and in water falls into powder
without forming a paste.   This contains most impurities.

  All the above species of carbonate of lime, will in high
heats part with their carbonic acid.   The quantity they part
with  can be ascertained by heating them in a retort, con-
nected to a pneumatic tub,  and receiving  the  air.  One
hundred parts  of these will be found to contain, generally
about 40 parts  carbonic acid  and 50 of lime. 
  DISCOURSE  VI.               183

PLASTER OF PARIS ;
           OR
SULPHATE OF  LIME.
  THE sulphuric  acid unites  to  lime, forming  the well
known  substance,  called  plaster  of Paris, gypsum, sele-
nite, or more  properly termed sulphate  of lime.   It is
found in great quantities  in nature, existing in  immense
masses,  and also diffused through  various soils  and waters.
In masses it is met with in various states either in a pow-
dery form,  or state of hardness,  forming varieties  either
white, grey,  yellow, green, or red.  Sometimes they con-
tain chalk,  which may be  detected by adding a strong acid,
which will disengage the  carbonic acid.  When good it is
composed of about 35 parts lime,  45  sulphuric acid, and
20  parts water.

   Plaster of Paris is soluble in  500 times  its weight of
 water,  at a temperature of 60°.  Exposed to  heat  it ap-
pears to boil or effervesce, in consequence of the extrica-
tion of the water it contains ; afterwards it becomes opaque
and falls into a white powder.   This powder,  when mixed
with water  absorbs it rapidly, and though of the consist-
ence of cream, it  becomes soon  solid by a  kind of crys-
tallization.   In  consequence  of this, it  is frequently put
 in  moulds made in  fanciful shapes, the forms of which it
 acquires and retains, so that  they serve for ornaments.—
 This is called plaster or stucco work.  This  compound has
 been lately  extensively used  as a manure,  particularly  in
 the cultivation of  clover with great success.  The  indust-
 rious  and  respectable  Mr.  Binns,  of Loudon county,
 Virginia, has published  some interesting facts concerning
 on its use as a manure in a small pamphlet. 
184
DISCOURSE VI.
               NITRATE OF LIME.


  THIS compound, as its name indicates, is composed of
the nitric acid and  lime.  It is found in great  quanti-
ties about old buildings,  and is used chiefly  as  a manure,
and to separate the nitric acid  from it.   This is done by
simply adding potash to it,  which unites to the acid form-
ing nitre, which is dissolved in water.
MURIATE OF LIME.
  THE  muriatic acid unites to lime, forming a neutral
salt, which has been employed to create most intense cold-
ness, by mixing it with snow.  If a  saturated solution o£
it in water, be added to a saturated solution of the carbonate
of potash in the same fluid, the two instantly become solid,
because the carbonic acid unites to the  lime and the muri-
atic acid to the potash,  and in crystallizing render the water
solid.
DERBYSHIRE SPAR,
           OR
   FLUOR  SPAR,
           OR
 FLUATE OF LIME
  THE fluoric  acid is found in nature  united  to  lime
forming Derbyshire or fluor spar,  more properly called 
DISCOURSE VI.               185
fluate of lime.   It is employed to yield the fluoric acid.—
Greatest quantities of it are met with in England, in the
 county of Derbyshire:  hence its vulgar name.
PHOSPHATE OF LIME.
   THE phosphoric acid is found united to lime  in nature,
forming  the  fossil called apotite,  which  is generally red,
grey, green  or  purple  colored with  some lustre.   The
bones of animals consist chiefly of the phosphate of lime,
from which the phosphoric acid is obtained, as stated while
 considering phosphorus.

   Lime is  also capable of uniting to all  other acids, and
forming  compounds which  should be  named  according
to the acid.   These compounds have not exited much at-
tention,

  Besides the acids, lime combines chemically with sulphur
and phosphorus, forming a sulphuret  and  phosphuret  of
lime.  The first is said to have the properties of the alka-
lies.   Phosphuret of lime may be made by heating the lime
with phosphorus in a tube.   This compound decomposes
water when introduced in it, and forms phosphorated hidro-
gen air, which burns on coming in contact with  atmosphe-
ric air at the lowest temperature.   Lime also by fusion  u-
nites to alumine, silex,  and  barytes,  and renders  these
earths very fusible, as has been before observed.
                         A a 
DISCOURSE VI.
MORTER.
  LIME forms the principal part of the  morter,  or  ce-
ment, used for  connecting stones and bricks  in  buildings.
It is generally made of  lime, sand, and water. It becomes
solid in consequence of a kind  of crystallization,  and  a
slow absorption of carbonic acid from the air.  No  certain
proportion of lime, silex, and water, for forming morter, is
adhered to in this  country.  It  is,  however, stated that the
best morter is made of  one part lime and two of sand, with
as much water as  is necessary to give it consistence, which
are to be most minutely beaten or mixed together.

   Guyton de Morveau states that an excellent morter may
be made of the following ingredients, which has the pro-
perty of hardening under water.  Take four parts  of blue
clay, six of black manganese, and  nine of chalk, finely
powdered,  and expose them to a strong heat.  To this sixty
parts  of sand should then  be  added,  and the whole made
into a paste with a sufficient quantity of lime water.

   From a late discovery of Dr. Higgensj it has been prov-
ed that  burnt bones has a most happy effect in increasing the
virtues of morter.   According to the Doctor's direction,
55 parts of  washed coarse sand, whose single grains do not
exceed  one sixteenth  part  of an inch  in diameter,  and
forty-five of fine  sand  should be mixed together, and wet-
ted with lime water.  To this 14 parts  of  slaked lime are
to be  gradually added  and well beat  together, and  lastly,
the same quantity of powdered bone  ashes.  The addition
of manganese, it  is stated,  uniformly give6 to morters  the
property of  hardening under water. 
                   DISCOURSE  VI.               1.87
                   IV. MAGNESIA.


   MAGNESIA is not found pure in nature, but is obtain-
ed by art  from some of its combinations.   It gives a pecu-
liar  character to most of the substances with  which  it is
combined.  The stones containing this earth in considerable
quantities have, generally a  smooth and unctuous feel, a
greenish cast,  a fibrous texture,  and a silky lustre. Among
them may be mentioned talc, soap rock,  serpentine,  asbes-
tos,  mountain  cork, jade or mephitic stone, boracite, &c.
This earth is also found united to acids, diffused in sea-wa-
ter and in some sea plants.

  Magnesia may be had in a  state of purity from  the water
left after  the  extraction of  salt  from sea-water.  To this
water the substance called copperas,  which is composed of
sulphuric  acid and  iron, is to be added. The sulphuric  acid
unites to the magnesia, forming Epsom salt, or the sulphate
of magnesia, which may be crystallized  by  evaporating
part of the water.   This sulphate of magnesia should be
again  dissolved in water,  and the  carbonate of soda be
added to it,  so  long as a white powder falls to  the bottom.
This white powder is  the magnesia sold in the shops.  It
is formed  of the  carbonic acid and magnesia,  and may be
freed of the carbonic  acid,  by heating it in a  tight vessel,
until it ceases to effervesce,  when strong acids are applied
to it.

  Pure magnesia does  not form  with water an adhesive
paste.   It is in the form of  a very  white spongy powder,
soft to the touch, and perfectly tasteless.  It is  very slightly
soluble in water.   It  absorbs  carbonic  acid from our at-
mosphere  ; changes some blue  vegetable colors  to green.
Its specific gravity is about 2. 3.   It is infusible alone, but 
188
DISCOURSE  VI.
not so when blended with other earths.  When heated
strongly, it beco.nes  phosphorescent.  It unites to all the
acids, forming salts, very soluble, and possessing a  bitter
taste.  Its attraction however for the acids, is not equal to
the attraction of the alkalies for them.
          CARBONATE OF MAGNESIA.


  THE common uncalcined magnesia  of the  shops, is a
pure carbonate of magnesia.   It  may readily be  made to
part with  the carbonic  acid, by adding other acids,  or by
means of heat.   In the last instance it forms what is called
calcined magnesia.  The  Magnesia of  the shops is made
in considerable  quantities, by adding to saturated solutions
of Epsom salt,  or sulphate of magnesia, the carbonate of
soda, when the sulphuric  acid unites to the soda, forming
Glauber's  salts, and the  carbonic acid  to the magnesia,
forming common magnesia.   One  hundred parts of it are
composed of about 50 parts of the earth,  30 of  the acid,
and 20 of water.  It is used chiefly as a laxative for chil-
dren, and to correct the acidity of the contents of the sto-
mach which cause heart-burn.  It  is remarkable, that cold
dissolves more of this compound than hot water.
        EPSOM  SALT;
               OR
SULPHATE  OF MAGNESIA.
  THE sulphuric acid unites to magnesia, forming the pur-
gative salt formerly much used, called Epsom salt, or more 
                  DISCOURSE  VI.               189

properly sulphate of magnesia.  This salt is made in consid-
erable quantities from Epsom's springs in England, whence
its name.  It is exceedingly bitter, and is used in doses equaL
to those of Glauber's salts.   It is now  chiefly employed for
the preparation of magnesia.   It differs from Glauber's salts,
in not turning into a white powder  when exposed to the air.
It is composed of 24 parts acid, 20 earth, and 56 water.
MURIATE  OF MAGNESIA.
  THE muriatic acid unites to magnesia forming a neutral
salt, very bitter, very soluble in  water, and which exists
in sea water, and is the cause of its bitter taste.

   All the rest of the acids unite to magnesia, and form
compounds,  wich have not been found of consequence.



                    V. BARYTES.
  THIS earth exists in nature in combination,  and compa-
ratively speaking, but in a small quantity.   It was first ob-
tained from  a body called heavy spar, which is found about
mines.   This heavy spar is composed of the sulphuric acid
and the earth barytes.  The earth may be obtained from it
in a state of purity, by pulverising  it and boiling it in a
solution of the carbonate of potash, in a Florence flask for
two hours.   The solution is then"to be filtered,  and expo-
sed to a strong  heat in a retort. 
190
DISCOURSE VI.
  Pure barytes has a stronger affinity for the sulphuric acid,
than it has for any other body;  and consequently it serves
to detect the  presence of the acid.  For this purpose it is
employed in combination with the muriatic acid,  as it parts
with the  muriatic to unite to the sulphuric acid.

  Barytes is  infusible alone, but not so,  when combined
with other earths.  Its specific gravity is  4.00.   Exposed
to the air and moisture,  it slakes  much more rapidly than
lime.   It unites to phosphorus,  forming a compound which
decomposes water more quickly than the  phosphuret  of
lime.   It is soluble in 20 times  its weight of cold, and
twice its weight  of hot water.   It unites to all the acids,
forming  compounds,  which have  not yet  been found of
great  consequence.   Its  union  with the  muriatic acid,
forms the muriate of barytes,  which a few have thought
useful in scrofulous affections, in doses from 5 to 50 drops
per day.   In  general it is a very fatal poison to animals.
VI. STRONTITES,
  THIS is an earth, discovered lately at Strontian in Scot-
land,  from whence it takes its name.  It was for some time
confounded with barytes, and indeed it resembles  barytes
so much in its properties, that what  was said  of the  one
will apply to the other.   It is found but in small quantities,
and united to the sulphuric and carbonic acids.  The neu-
tral salts it forms, differ from those of barytes, are  less in-
jurious  to  animals, and  have not been  found of  conse-
quence. 
                   DISCOURSE VI.                191

                   vn. ZIRCONE.




   THIS is a new earth, lately discovered in the Zircon or
Jargon, a gem first brought from the island  of Ceylon,  but
also  found in Europe.  Its color is either  grey, greenish,
yellowish, redish, brown, or purple.

   Zircon is a remarkably heavy earth; its specific gravity
being 4.  3.   It unites to all the  acids, and  it has not  yet
been found of any  consequence in the arts.
VIII. GLUCINE.
   THIS earth also has been but lately discovered in a few
gems,  such as the  emerald of Peru.   Its specific gravity is
2.967.  It unites  to the acids, forming neutral salts,  re-
markable  for a slightly sweet  and astringent taste__hence
the name of the earth.  It is soluble in the alkalies.
IX. YTTRIA.
  THIS  is  an earth discovered also not long since.   It is
the heaviest  earth known; its specific gravity being 4.840. 
192
DISCOURSE VI.
It has been found  but in small quantities,  and in some of
its properties resembles glucine.

  Besides the  above earths, there are one  or two more
spoken of by some authors.  Agustine is a name applied to
one earth, which several consider  as a distinct earth.  No
doubt but that  many may meet with compounds which they
cannot decompose; but before such are ranked among the
elements,  they  should be met with by many chemists.  It
must at once appear, that  the only earths  found of great
consequence, are those first treated  of, which are,  silex,
alumine,  lime, magnesia,  and barytes.
 
DISCOURSE VII.
   HAVING considered the  most striking qualities of the
bodies termed earths, we proceed to treat of the remaining
parts of the globe, which are called metallic bodies, or me-
tals. The properties of these metals, differ materially from
those of other substances;  but they are of not less impor-
tance in the creation.  Without them, the arts and sciences
could never have arrived  at their present state of perfection.
Such was the value placed on them by the  ancients, that
those who first acquired  the  art of  working  them,  were
raised to the rank of deities.   At one period, chemical re-
searches were confined solely to the metals; and the science
has received its existence from the rage to transmute them
or convert the common kind, into gold and silver.

   Metals are distinguished from all other bodies by remark-
able qualities.

   1. Their  specific gravity is greater than  that of other
bodies.  The heaviest body, not  metallic, has not a specific
gravity exceeding 4:5;  while that of the lightest  metal is 
194               DISCOURSE VII.
6.702.  This specific gravity is  increased by hammering
the metals

   2. They are more opaque,  or resist the passage of light
 more than other substances.

   3. They possess greater  lustre or brilliancy than other
 bodies, in consequence of reflecting more light.

   4. They  are remarkable for malleability, a property by
 which  is  meant  their capability of being hammered into
 thin plates or leaves.

    5. Also, for their ductility, by which is meant their capa-
 bility  of being drawn into wires.

    6. They are more fusible, at least, than earths.

     7. Their hardness is greater than that of most substances.

     8.  They are the best conductors  of electricity, heat and
  galvanism.

     But these  properties, in  different metals, are found to
  differ considerably.   For example; mercury is always fluid
  in a heat above  40° below 0°: while it is only in the high-
  est heat, platina  can be fused.

     The pure elementary metals are remarkably susceptible of
  combination. This tendency to combination  is so strong, that
  it is seldom they are found in a pure state.  When they are
  found in a pure state, or only united to each other, they are
  said to be native.  When they are found united to sulphur,
  oxigen,  or  any other body, they are said to be mineralized.
  They  are always found in the bowels of the earth, in which 
DISCOURSE VII.               195
state they are called ores.  The ores of metals are generally
found in mountainous parts, and forming a continued chain,
in the crevices of rocks, which are termed by miners veins.
The metallic matter is commonly mixed with some earth,
different from that of the rock, in which the ore is found :
this  is termed its matrix.  To obtain the metal, the matrix
is separated  by  pounding,  washing, or other mechanical
contrivances; or by roasting and then melting them in con-
tact with the fuel.   The  art of extracting metals is called
metallurgy.

   The metals unite to each other chemically, and form com-
pounds called allays: This union is usually effected by heat.
These  allays always possess the metallic  properties; but
differ considerably in their gravity, hardness, fusibility, &c.
from the metals of which they are formed.

   The metals are to be considered as oxidable, or combusti-
ble bodies.   They  unite  to oxigen in various proportions,
and with different degrees of rapidity; some doing it very
slowly, and others so rapidly, as  to blaze, or throw out heat
and light.   If lead, or iron  be melted while  exposed  to
this air,  it will gradually  lose its metallic properties, and
appear something like an  earth.   This is in consequence of
its uniting to oxigen. The product was formerly called a calx,
but more properly at present an oxid.  The process is term-
ed oxidation.   These metallic oxids may be made to give up
their oxigen, if heated in close vessels;  particularly if in
contact wth  charcoal, and then they re-assume the metallic
state.   One  hundred parts of a few of  them  contain near
50 parts of oxigen: but most of them contain much smaller
quantities.  The color of the oxid, varies with the quantity
 of oxigen it  contains. 
196               DISCOURSE VII.
  The metals, after they are reduced to the state of oxids,
axe capable of uniting to the acids,  forming neutral salts,
which have been called metallic salts.  Unless the metals be
previously united to oxigen,  they cannot combine with the acids.
Some  acids, however,  when added to  metals, part with
some oxigen, to oxide them, and then combine with them,
forming metallic salts.   Some of the metals unite to such
large quantities as to form  acids,  as will hereafter appear.

   The difference in the properties  of metals has given  rise
to their classification.  Some  of them are  called, noble or
perfect metals, imperfect and semi-metals, brittle and malleable
metals, Nc. But these divisions are defective  and useless.
I  shall consider them in  the order  in which they will be
enumerated.

   Concerning  the number of pure, simple, or elementary
metals, in nature, authors have not determined. Some state
that there are but  20, others 21, 22, and a few 23.  Those,
however, of which they are doubtful, are of no consequence;
as is the case  with some which they have described. I shall
pursue my plan of devoting to each  the attention to which
it is entitled from its  known virtues.



    NAMES  OF  THE ELEMENTARY  METALS,
1 Mercury,
2 Platina,
3 Gold,
4 Silver,
5 Copper, 
DISCOURSE VII.               197
 6 Iron,
 7 Tin,
 8 Lead,
 9 Zinc,
10 Bismuth,
11 Antimony,
12 Arsenic,
13 Manganese,
14 Cobalt,
15 Nickel,
16 Molybdena,
17 Tungsten,
18 Uranium,
19 Titanium,
20 Tellurium,
21 Chrome,
22 Columbrium.
FIRST METAL
MERCURY.
  MERCURY, or quicksilver, is a metal  distinguished
from all others  by its  fluidity in a common temperature.
It is only at 40° below 0°, that it is solid.   It may be vola-
tilized at a temperature of about 500°.

  This metal is found in different states in nature.  In se-
veral parts of the world, it is found mixed with various sub-
stances as oxigen, sulphur and silver.  United to oxigen it
forms the hepatic ore;  with  sulphur, it  forms native ethiops
and cinnabar. The ethiops, is of a dark color, without trans-
parency or lustre, and is of a loose consistence.   The cin- 
198
DISCOURSE  VII.
nabar is of a red color, with considerable lustre in masses,
which when  reduced to a  fine powder is sold  in  com-
merce under the name vermillion, and is much used as a
paint.   This may be prepared by the direct combination of
sulphur with  mercury,  aided  by the application of heat.
Combined with  silver, it  forms the ore called amalgam of
silver, which  is of a silver white or grey.   These ores are
found in great quantities in South  America, Spain,  Hun-
gary, and China.

   In order to obtain mercury from its ores, it is necessary
to employ heat.  When the mercury is mixed with sulphur
or oxigen, it should be heated in a retort, with one  third its
weight of the filings of iron,  or  lime, and on  applying
heat, the mercury rises and comes over, in the vessel con-
nected to it.   When the mercury is united to another me-
tal,  it is only  then necessary to  distil it in a proper vessel.

   Mercury in its metallic state unites to various metals, for-
ming  important compounds,  called amalgams, which will
hereafter be  considered.  It may be divided into very small
globules. It undergoes slowly an evaporation, when uncover-
ed in common temperatures.   It is an excellent conductor
of heat, electricity,  and galvanism.  Its specific  gravity is
13.563.   Although a fluid,  its opacity is  equal to that of
any  other metal.   When clear, its  surface has considerable
lustre and resembles  silver.  When agitated in the air, es-
pecially with thick fluids, it becomes of  a black color.  At
the temperature  at which it bods,  it absorbs about 15 per
cent, of oxigen, and is then changed into a red oxid, which
may be freed  of its oxigen by heating it in  a close vessel.
When reduced to the state of an oxid,  it is capable  of u-
niting to all the acids, and forming compounds possessing
various properties.  At one time the shops  were  crowded
with the various preparations of mercury ;  but as  the rage 
DISCOURSE VII.
199
for such a variety has fortunately subsided, only a few are
retained,  from which every good may be derived.  These
are called,  red  precipitate  or  nitrate  of mercury,  corro-
sive sublimate or oxi-muriate of mercury, and calomel or mu-
riate of mercury.
   RED PRECIPITATE;

             OR

NITRATE  OF MERCURY.
  THE nitric acid when poured on mercury, parts with a
portion of its oxigen, which unites to the mercury forming
an oxid;  the remaining acid unites to this oxid of mercury
and forms the nitrate of mercury or red precipitate, which
when heated crystallizes into a red mass of a brilliant ap-
pearance.   This is chiefly used as an application to callous
sores.



            CORROSrVE SUBLIMATE;

                          OR

         OXI-MURIATE  OF MERCURY.
  THE corrosive sublimate of the shops is thus formed.
In glass vessels the sulphuric acid is boiled on mercury, until
the metal is oxided, and then united to the sulphuric acid, 
200
DISCOURSE  VII.
forming the sulphate of mercury.  To the sulphate of mer-
cury a  quantity  of dried common  salt  is to  be  added.
These are to be introduced in  glass vessels, and gradually
exposed to a strong heat.   In this  case, the muriatic acid
of the salt unites to the oxid of  mercury,  forming the cor-
rosive sublimate,  which sublimes and adheres to the upper
part of  the vessel.   The sulphuric acid unites to the  soda,
forming Glauber's salts, or sulphate of soda, which remain
at the bottom of  the vessel.  The vessels are to  be broken,
and the sublimate taken out and pulverised.   It then con-
stitutes the corrosive sublimate of the shops,  which is ap-
plied in weak solutions in water to eruptions,  sores, &c.
It is soluble in 16 times its weight of water, but in much
larger quantities when ardent  spirit or  sal-ammoniac  is
added.
         CALOMEL;

              OR

MURIATE  OF MERCURY.
  IN order to prepare calomel, it is only necessary to rub
together equal parts of corrosive  sublimate and pure mer-
cury until the mercury entirely loses its metallic appear-
ance.  In this case,  the  mercury abstracts a part  of the
oxigen from the corrosive sublimate, which lessens its ac-
tivity,  and converts it into calomel or muriate of mercury.
This preparation is quite insoluble in water, and to  be pu-
rified must be repeatedly washed in water.  It is used to
excite salivation in small doses;  and in doses from  10 to 20
grains it is an admirable cathartic. 
 DISCOURSE VII.               201

SECOND  METAL.
                      PLATINA.

  THIS is a metal which has only been found in the mines
of Peru, intermixed with gold and iron.  It is met with in
a native state in the form of small grains.  When pure, it
is of  a white color,  like silver, but not so bright.   Its spe-
cific gravity is between 20.6 and 23. so that it is considera-
bly the  heaviest body known.   It is very ductile,  or may
be drawn out into very small wires ;  and is very malleable,
or may be hammered into very thin plates.   For its fusion
it requires a most intense heat, and in fact cannot be at all
melted  in common furnaces.   In high heats,  however, it
becomes soft, and may  be welded together as iron.  Since
Mr. Hares' use of hidrogen air to generate heat has been
suggested,  it is probable that large quantities of this metal
may be  hereafter melted and applied  to useful purposes,
such as making vessels to resist the action of intense heat.
Platina unites to  most of the metals forming alloys,  most
of which, however, have not been attended to.  The metal
is valued chiefly for its great hardness,  infusibility,  and not
being tarnished on exposure to air.

  Platina,  it is said in an intense heat, and  in oxigen air,
unites to oxigen forming an oxid of platina, which may be
dissolved by the acids.   This metal is also oxided in the  ni-
tro  muriatic acid,  formed by the  muriatic and nitric acids,
and is then dissolved.  On adding to this solution the muri-
ate of ammoniac the platina is precipitated, by which property
the metal may be distinguished from every other one.
c c 
202               DISCOURSE  VII.

                   THIRD METAL.


                        GOLD.

   GOLD is a metal which has long since been known and
 highly valued.   It is found in the metallic state, seldom per-
 fectly pure,  but mixed with silver,  copper,  iron, and ar-
 senic, forming alloys.  It is met with in the sands of many
 rivers, particularly in Africa, Hungary, and  France, in small
 grains called gold  dust.   The largest piece of native gold
 ever discovered in Europe, was found in Ireland, its weight
 being 22 ounces.   It has been found united  to sulphur in
 Transylvania.  In North Carolina considerable quantities
 have lately been found in mines,  in the  metallic state ;  and
 the prospects of its proving of great value were so  flatter-
 ing, as to induce the benevolent and enterprizing Dr. Thorn-
 ton of Washington city,  to establish a company for procur-
 ing the gold.  But the chief part of  the gold in circulation
 has been obtained from the mines of South America.

    When gold is found native, or in other words, in the me-
  tallic state, it exists in small grains,  blended with  sand
  and other bodies.   In this case the miners place it  where a
  gentle  stream of  water passes over it, and washes away
  most of the lighter impurities.   It is then put  in a mortar
  and rubbed up with one tenth of mercury,  until  the two
  metals  unite  together.   The whole is  then  put on a table
  placed  in an  inclined direction,  and the mercury  with the
  gold runs off.  ft is then put in a retort and strongly heated,
  when the mercury flies off, and  leaves the gold behind.—
  Sometimes the gold so obtained, contains  silver, of which
  it may  be freed by reducing it to thin plates, and putting it
  in the nitric  acid,  which dissolves the silver, but does not
  act on  the gold.   The  silver may then be procured from 
                   DISCOURSE VII.               203
the nitric acid by  adding to it muriatic acid,  which unites
to the silver.  This muriate of silver is then to be mixed
with soda and exposed to a strong heat, when the muriate of
soda is formed and the silver remains pure.

   When gold is found mixed with sulphur or arsenic,  the
ore should be torrefied ox roasted, by which these substances
are volatilized.   The ore should then be washed and mix-
ed with lead and melted, so that an alloy of  gold and lead
is  formed.  This is then to  be heated in a vessel called a
cupel, which is porous,  and  is  made  of  burnt  bones.
The lead melts  and  passes  through the cupel, while the
gold remains pure.   Perfectly pure  gold may  be had by
dissolving the gold of commerce in the nitro-muriatic acid
and precipitating it by adding a weak solution of the sulphate
of iron.   The precipitate when  washed and dried is pure
gold.  When it is designed to ascertain if this metal exists
in any ore, the ore should be rubbed up with the nitro-mu-
riatic acid,  and then a little of a solution on the  muri ite
of tin should be added.   If the solution contain any gold,
a purple precipitate immediately appears,  which is an oxid
of gold.  If it contain any iron, it  will become black  on
adding a tincture  of nut galls.  If it  contain silver, it may
be precipitated by adding a little muriatic acid.   And the
presence of copper may be detected by keeping a plate  of
iron in it for some time.

   The properties  of pure gold  are  very generally known.
It has a rich brilliant yellow color,  and is the heaviest body
in nature excepting platina.   Its specific gravity is 19.3.  Its
hardness  is not  very considerable.   Its  ductility is very
great, and  its malleability is such,  that  one grain  of  it
may be made to  cover 56,718 square inches.   It  melts at
32° of Wedgewood, may be volatilized in  a higher heat,
but is incapable of uniting to the oxigen of the air in any
temperature.   Electricity  and  galvanism inflame  it, and 
204
DISCOURSE  VII.
convert it to a purple oxid, which flies off in the form of
smoke.   It unites to most  of the metals forming different
alloys.  It is soluble in  the sulphuret of soda and potash,
and can  then be dissolved  in water; and by this process
it is supposed Moses destroyed the golden calf.

   Gold  is not oxided by any of the acids, excepting the
nitro-muriatic, called  also oxi-muriatic  acid.   After  this
acid oxides it, the gold  is dissolved in it.  It may then be
precipitated in the state of an oxid, by several substances ;
as the alkalies, lime,  magnesia, tin, &c.  When a  shtet of
tin is added to a solution of gold, the gold is precipitated in
the form of a powder, which is called the purple powder
of Casius, which is used in coloring porcelain.  When
it is precipitated by means of ammonia,  a powder appears
of a yellow color.  This  is called  fulminating gold.  It
contains a little ammonia; and if washed and dried, when
gently heated, it detonates, in consequence of a decomposi-
tion of the  ammonia and  extrication  of  its  nitrogen air.
However, the various compounds, formed by the acids and
 gold, have not been much examined.

   The uses to which gold is applied, are  generally known.
 Commonly  that used as a coin, is adulterated  with silver,
copper or platina. From the beauty of its color, it is employ-
 ed variously for  ornaments.   When drawn  into very fine
 wire, it  is used  in embroidery.
CONCERNING GILDING.
  BY gilding is meant the art of covering the surfaces of
bodies  with gold.  Some use the term to denote silvering 
DISCOURSE VII.
205
also, but improperly.   This application of gold to the sur-
face of other metals,  so as to give them  its color, is vari-
ously effected, as will appear from the following.
       SHELL GOLD,  OR GOLD POWDER

For painting, may be  made  by uniting one part of gold
with eight  of  mercury, and then evaporating the mercury
by means of heat,  which leaves the gold in  the form of
powder, in which state it is applied to the surfaces of bodies.
GILDING BY FRICTION.
  LET a fine linen rag be steeped in a solution of gold-for
some minutes, then let this rag be dried and burnt. When
any thing is to be gilt, it must previously be well burnish-
ed : a piece of cork is then to be dipped, first into a solution
of salt in  water, and afterwards, into the black powder.
The substance to be gilt, is  then to be rubbed with it and
burnished.  This powder is frequently used for gilding de-
licate articles of silver.
GILDING OF BRASS  OR COPPER.
  FINE instruments of brass, in order that their surfaces
may be kept clean the longer, may be gilt by immersing them 
206               DISCOURSE  VII.
several times in a solution of gold, free from excess of acid,
and afterwards they are to be burnished or polished.
WATER GILDING,
  THIS term was probably at  first confined to such pro-
cesses as demand the use of a solution of  gold in nitro-
muriatic acid, and means a  chemical application of gold
to the surface of metals.   If a solution of gold be copiously
diluted  with  ardent spirit, a piece of clean iron will be gilt,
by  being repeatedly steeped therein.  But  a much better
method is the following :  pour into a solution  of gold, in
nitro-muriatic  acid, about twice  as much sulphuric ether.
In order to gild iron or  steel, the metal must be well po-
lished, with the finest emery or red oxid of iron and spirit
of wine.  The ether which has taken  up  the gold, is then
to be applied with a small brush;  it evaporates, and the
gold remains on the surface of the metal;  the metal may
then be put into the fire, and afterwards polished.   In this
manner, all kinds of figures  may be delineated on iron, by
employing  a pen or small'brush.  Iron  is also gilded by
means of heat.  For this purpose, the iron must be  heated
till it has acquired a blue color.  When this is done, the
first layer of gold leaf is put on,   slightly pressed, and ex-
posed to a  gentle fire. It is usual to give three or four such
layers,  and  the heating  is  repeated at each  time,  and
lastly, the work is burnished. 
DISCOURSE VII.
207
                GRECIAN GILDING

  Is thus performed : equal parts  of sal-ammoniac and
corrosive sublimate are dissolved in nitric acid, and in this
gold is dissolved.  Upon this, the solution is somewhat con-
centrated, and applied to the surface of silver, which be-
comes  quite  black;  but on exposure to a  red  heat, it as-
sumes the appearance of gold.
GILDING COPPER, SILVER OR  BRASS;
                      BY
           THE AID OF MERCURY.
   FOR  this purpose,  eight parts of mercury, and one of
 gold  are  alloyed,  by heating them together.   When the?
 gold is all dissolved, the mixture is put into cold water, and
 is then fit for use.

   Before  the  alloy  is  laid  upon  the  surface of the
 metal, this last is brushed over with diluted nitric acid, in
 which it  is of advantage,  that  some mercury may have
 been dissolved.  The alloy must then be laid on as uni-
 formly as possible,  and spread very even with  a  brass or
 wire brush,  wetted from time to time  with  water.  The
piece is then exposed to heat, which driven off the mercury
 and leaves the gold behind.   Its defects,  if any appear, are
 to be  remedied by the application  of  more  of the alloy.
 The whole  is then polished  or rubbed over with gilders'
 wax;  which is made of one ounce of verdigris and cop-
 peras, with  four ounces of bees wax;  and the last is to be
 burnt by exposure to heat. 
208
DISCOURSE  VII.
  PAINTING WITH GOLD  UPON PORCELAIN
                   OR  GLASS,

Is done with the powder of gold, which remains behind
after driving off the nitro-muriatic acid, from a solution of
that metal.  It is laid on with borax and gum water or  oil
burned in and polished.
           THE GILDING OF  GLASS

Is commonly effected by covering a  part with a  solution
of borax; and applying gold  leaf upon it, which is after-
wards fixed by burning.
        THE EDGES OF TEA  CUPS, &c.

Are frequently gilt in a less durable manner by applying a
very thin coat of amber varnish, upon which gold leaf is to
be fixed, and when the varnish dries the gold is burnished.

  The gilders of  wood  and other compositions, designed
to supply the place of carved work,  make use of gold leaf,
which is either laid on with size  or boiled oil, and after-
wards burnished. 
DISCOURSE  VII.   •
209
FOURTH  METAL.
                      SILVER.

  THTS metal is familiar to every one.   It is found in the
metallic state, united to lead, antimony,  copper,  mercury,
and arsenic ;  and it is fouad mineralized with sulphur and
the arsenic acid.  The  mines yielding most silver, are in
South America, Germany, Norway and France.

  Silver is obtained from its ores in different ways.   In
Peru and Mexico, the  mineral is pounded, roasted  and
washed, and then rubbed up with mercury in vessels con-
taining water.  The mercury and silver  unite forming an
alloy, which  is afterwards  to  be washed  and then pres-
sed through leather.   This being done heat  is applied to
drive off the mercury from the silver, which is then melted
and cast into bars.

  In other cases the silver is extracted,  after the mineral
is roasted,  by melting it with lead and  borax ;  the silver
unites  to the lead forming an alloy.   This alloy is to be
heated in a porous bone vessel, called a cupel;  in which
case the lead melts through and leaves the  pure silver in
the cupel.

  When it is designed  to  detect the presence of silver in
ore, the ore should be dissolved in the nitric acid;  and on
adding common salt, the silver will be precipitated in  the
form of muriate of silver, which is to be heated to be freed
of its acid  and oxigen.                       %
                          Dd 
210
DISCOURSE VII.
  The properties of pure silver  are familiar to most peo-
ple.   It is next to gold in malleability, ductility,  and lus-
tre.   Its color is white ; its specific gravity is 10.450, and
its hardness is  considerable.  It melts at 28° of Wedge-
wood, and  in a higher temperature it becomes voLtilized.
Atmospheric air has no effect on it, unless sulphureous va-
pors be contained in  it.  It unites to  phosphorus and sul-
phur.   It  unites  to other metals  forming various alloys.
With gold it forms what is  termed green gold.   It unites to
oxigen, forming an oxid which unites  to all the acids, form-
ing various compounds.   These compounds  may  be de-
composed by the earths and alkalies.


   Silver is oxidated  very  readily in the nitric acid.   This
will  appear by pouring the acid when moderately  strong,
on silver in a Florence flask, an effervescence will take place,
the nitric acid will be decomposed, oxigen will unite to the
 silver,  and nitrous air  will come over.  This oxid of sil-
 ver will then be  dissolved in the remaining nitric acid.   If
 this  solution be  then evaporated it  shoots  into crystals,
 which are called  nitrate of silver, but  more commonly caus-
 tic.   It is applied by surgeons to callous ulcers.  It has the
 power of  staining animal and vegetable substances of a
 deep and lasting black; hence, it has been used  for  stain-
 ing human hair, but when thus  used, it should be very
 much diluted in water as it has a corrosive property.  The
 article sold in the shops by the term indelible marking ink,
 for marking wearing apparel, is nothing  more than a solu-
 tion  of this caustic in water,  thickened with a  little gum
 arabic.   The fluid called the silver test, for detecting coun-
 terfeit coin, is a  solution of pure silver, considerably dilu-
 ted.   This compound is decomposed and the silver  preci-
 pitated by the addition of copper. 
DISCOURSE  VII.
211
   The muriatic acid has a stronger attraction for the oxid
of silver than the nitric acid.   Hence, on adding the mu-
riatic acid to a solution of  the nitrate  of  silver, this last is
decomposed.   The  muriatic  acid unites  to the oxid of sil-
ver,  forming  the muriate  of silver, which is an insoluble
compound,  called horn  silver.   This, heated  with three
parts of soda, is decomposed, and common salt and pure
silver are left in the retort.

   The sulphuric acid boiled  on  silver oxides and dissolves
it.   Mr. Keir  made the valuable discovery, that the sul-
phuric acid mixed with a little common  nitre,  or  nitrous
acid, when heated on silver,  dissolved the silver very rea-
dily, but did  not act on other metals.  In consequence of
this, the silver may  be had perfectly pure in large  quanti-
ties, by precipitating it with common  salt, and heating the
precipitate,  as is now done at the manufactory of coin at
Birmingham in England.

   There is a preparation of silver,  called Berthollet's Cul-
minating  silver, or ammoniated oxid of silver, which is the
most dangerous preparation  known.  It  is formed by pre-
cipitating a weak solution  of  the nitrate  of  silver,  by
lime  water.   This precipitate is then to be  mixed with
liquid ammonia, and stired until it assumes a Hack color,
then the fluid is to be  poured off, and the black compound
to be left in the open air to be dried.   This product when
ever afterwards  moved, most violently explodes.   It ex-
plodes without fire, and by the mere touch of any substance.
But  one grain must  be prepared at a time, and that with
great caution,  or the danger will  be considerable.  The ex-
plosion is in consequence of the  decomposition of the am-
monia ; its hidrogen  unites to the oxigen of the oxid of silver
forming water, which with the nitrogen are instantly rare- 
212               DISCOURSE VII.
fied by the heat.  The rest of the  combinations of silver
have not been much examined.
SILVERING.
  THERE are various methods of giving a covering of sil-
ver to the surfaces of bodies.

   Copper may be silvered by rubbing it with the following
powder: Take two drams of the cresm of tartar, the same
quantity  of common salt, and  half  a dram of  alum, and
mix  them well with 15 or 20 grains of silver precipitated,
from the nitrate of sUver  by copper.  The surface of the
copper becomes white when  rubbed  with this  powder,
which  may  afterwards be brushed off and polished  with
father.

   The saddlers and harness  makers, silver their wares as
follows : Half an ounce of silver, precipitated from the ni-
trate oi silver by  copper,  is to be  procured;  also  com-
mon salt and sal-ammoniac, of each two ounces, with one
dram of tie muriate of mercury, are to be rubbed up toge-
ther ; and Made into a  paste with water:  copper utensils
of every  kind, which have been  previously boiled in a solu-
tion of alum and cream of  tartar, are to  be  rubbed with
this, after which they are made red hot and polished.

   Shell silver for the use of painters, is prepared  by rubbing
silver leaf with * little honey or gum arabic, which are after-
wards to be washed away.   This  being  done,  the silver
may be put on paper or kept in shells, whence its name. 
DISCOURSE  VII.               213
                      PLATING.

  THE covering of the surface of copper with silver, is call-
ed plating.    It  is thus done : Upon small bits of copper,
plates of silver are bound with iron wire, generally allowing
one ounce of silver to twelve of copper.   The surface of
the plate of silver is not quite so large as that of the copper.
Upon  the edges of the copper, not covered by the silver, a
little borax  is put, and by exposing the whole to  heat, the
borax  melts and  facilitates the  union between the copper
and silver.   The copper, with its silver plate, is then press-
ed under steel rollers, moved by machinery, and  is cut at
pleasure  for use.


                  FIFTH  METAL.
                       COPPER.

  THIS is a metal found in most countries combined with
arsenic, iron and other metals.  More commonly it is found
mineralized with  oxigen,  forming the red or ruby copper,
which exists in masses of a red color,  moderate lustre,
hard and brittle.   The green sand of Peru is  also an oxid
of copper   The carbonic acid united to  copper forms the
ores termed the mountain green, and mountain blue. This
metal is also found united to sulphur, and the sulphuric
acid.

  In  order to separate copper from its ores, it is necessary
to expose them to a strong heat, in order that all the volatile
 substances may fly off.  In close vessels the copper is then 
214
DISCOURSE VII.
to be melted  several times, and the last time a quantity of
charcoal should be added to it.

  When it is intended to ascertain if copper exists  in an
ore, the ore should be dissolved in the nitric acid, which
will unite to  the copper forming nitrate of copper, which
when heated with  potash is decomposed, leaving behind
the oxid of copper.

  Copper  is known  by  the following  properties : It is
of a reddish  yellow color,  is inferior in malleability and
ductility to silver,and has a disagreeable smell and taste pecu-
liar to it.  Its specific gravity is about 8.500.  It melts at
27° Wedgewood,  and if  exposed  to the air,  it burns with
a beautiful green flame.   It unites to the acids when oxided,
forming very poisonous compounds;  it unites to the metals,
forming very useful alloys, and likewise to sulphur,  form-
ing a sulphuret of  copper.
NITRATE OF COPPER.
  THE nitric acid when poured on copper oxides it, and
then dissolves  it,  forming the nitrate of  copper, which,
when the solution is evaporated, yields crystals of a fine
blue color.   If to a solution of  this compound a  small
quantity of lime be added, a green precipitate is formed,
which when washed and dned, and rubbed in a mortar with
about five part  of lime,  the mixture acquires a very lively
blue color, which is known by the term of blue verditer. 
DISCOURSE VII.
215
SULPHATE  OF COPPER;
             OR
     BLUE VITRIOL.
  THE sulphuric acid unites  to copper forming the sub-
stance called blue vitriol.   This is a salt usually prepared by
burning ores  of copper containing sulphur.   The sulphur
forms sulphuric acid and then unites to the copper forming
sulphate of copper,  or blue vitriol.  This is also found in the
waters of  copper mines.

  This salt possesses a very strong styptic taste. It is easily
fused by heat, which dissipates its  water of crystallization,
and changes its color to a bluish white.  The sulphuric acid
may be extracted by a very strong fire.  Lime and magnesia
decompose this salt, and the precipitate is of a bluish white
color. If it be dried  in the open air, it becomes  green:
ammonia likewise  precipitates the copper, but  the pre-
cipitate is dissolved nearly at the moment that it is formed ;
and the result is a solution of a beautiful  blue color, known
by the name of aqua celestis.  Blue vitriol u composed  of
about 30 parts acid, 43 water, and  27  copper.
              ACETATE OF  COPPER;
                          OR
                    VERDIGRIS.


  THE acetic acid (which gives the sourness to vinegar) unites
to copper, forming the acetate of copper, called commonly
verdigris. This is an article that  is prepared in considerable 
216                DISCOURSE VII.
quantities in France by laying thin sheets of copper separat-
ed a little from each other in a vessel, in which vinegar is
poured.   The oxigen of the air oxides the  copper,  which
then unites to the acetic acid  forming verdigris, which is
then scraped off, dried, and preserved for use.  Consider-
able quantities of  it are also prepared at Montpellier, by
fermenting the rufuse of grapes with sour wine.  The re-
fuse is laid in alternate states, with plates of  copper about
6 inches long and  5 broad.  In this state they are left for a
certain time, after which they are taken out and placed on
their edges in a cellar,  where they are sprinkled with  sour
wine.  In this situation the verdigris swells up, and is af-
terwards scraped off, put into bags and sold.   All the other
vegetable acids unite to copper when oxided.  Hence  the
strongest  vegetable juices may be boiled in copper vessels,
as the steam prevents  the air from oxiding them ;  but
when the boiling ceases the air then oxides the copper, and
sometimes the oxid renders the contents poisonous.  Hence
the propriety of removing the contents from copper vessels
so soon as the boiling  ceases,


              ARSENIATE  OF  COPPER.


   THE  arsenic acid  also unites to copper,  forming a last-
ing green compound, much used in painting.   This is pre-
pared by dissolving potash in heated water, and  saturating
it with the arsenic acid; then the  solution is to be filtered,
and a solution of  sulphate of  copper, called blue vitriol, is
to be  added gradually; a precipitate will appear,  which
when dried is used as a paint.

   Ammonia also unites to copper.   If copper  filings be
included  in a bottle of liquid ammonia and left exposed to 
DISCOURSE  VII.
217
the air, the copper is oxided  and is then dissolved in the
alkali.   This preparation of copper as well as some of the
above have been  used as a medicine in very  small  doses,
but in  large quantities they are very poisonous.

   Copper  is precipitated from its solutions by iron.   For
this purpose nothing more is required than to leave the iron
in a solution of copper, which need not be  strong.  The
phenomena may be rendered very surprising, by pouring a
solution of the blue vitriol, (sulphate of copper) upon the
clean surface of a bit of  iron; for this surface intantly be-
comes  covered with copper.  This has given rise to the er-
roneous belief that the iron was converted into copper.

   Copper unites with  most of the metals and  forms al-
loys, some of which are of great value.

   1. With arsenic it forms Tombac, which  is of a white
color.

   2. With bismuth, an alloy  of a reddish white color.

   3. With antimony, a  violet colored alloy.

   4. It  may be  combined with  zinc by fusion, and the
product is brass.   If the lapis calaminaris (which is an oxid
of zinc) be used, the Manheim gold is obtained.

   5.  Copper, plunged in  a solution of mercury, assumes
a white color, which arises  from  the  deposition  of the
mercury, on the copper.

   6. Copper melted with tin, forms bronze, or bell-metal.
 This  alloy is  more brittle, whiter, and  more  sonorous, 
818
DISCOURSE  VII.
in proportion to the quantity of tin that enters mto its  com-.
bination.   It  is used to make bells.  When it is intended
to be applied for the purpose of casting statues, or forming
great guns,  a larger portion of copper is required, because
solidity is very necessary in such cases.

   7. Copper unites to silver, which it renders more fusible.
One sixteenth of  the silver coin  is copper.   The two
metals melted together are used for solders.  Hence it is
that verdigris  is occasionally observed in pieces of silver,
at those parts  where joinings have been  made by means of
solder.

   8. Copper also unites to gold.  One twelfth of the gold
 coin is usually copper.

   Copper  is  very  much used in the arts.   All the boilers
 in dye houses, which are intended to contain compositions
 that do not attack  this metal, are made of copper.   It  is at
 present used as a covering for the bottom of ships.   Most of
 the kitchen furniture is made of it.   And its combinations
 with oxigen  and  the acids,  are  much used in the  arts,
 and in small quantities as a medicine.



                    SIXTH  METAL.
                        IRON.

  THIS exits  in larger  quantities  in  nature, than any
other  metal.    It  is  almost  universally  found in  the
mineial and animal kingdoms, and also in many vegetables. 
DISCOURSE  VII.
219
Its ores are numerous, and  most  of  them so generally
known, that it would be useless to  dwell on them.  The
names of the most remarkable are as follows :

          1 Black ore, .
          2 Argillaceous ore,
          3 Bog ore,
          4 Pyrites,
          5 Magnetic iron ore,
          6 Specular iron ore,
          7 Red ore,
          8 Brown ore,
          9 Carbonate of iron.

   However, by far  the most common ore, is that called
pyrites, in which the iron is united to  sulphur.'  This  ore
is found in almost every country: the ores are also common
in which  the metal  is united to oxigen,  with which it
is found combined in different quantities, forming various
colored oxids.

   In order to separate the metal from its ores, they  should
be heated in the open air,  so that the volatile parts may
escape; and then they are to be introduced in furnaces, in
contact with the burning fuel.   The iron melts and is al-
lowed to  run in the  sand, forming what is called pig, or
cast-iron, which is  very far from  being in a pure state.
Besides other substances,  it  always contains oxigen  and
carbon.  When the  oxigen abounds, the  iron is brittle;
white colored, and is  called  white crude iron.  When the
carbon abounds, the  iron is less brittle; has a dark grey or
blue color,  and is called black crude  iron.   The  iron in
these states, is  much more fusible than when pure ; hence
it may  be readily melted and cast into any form.   To pu-
rify  the iron, it is again melted and stirred frequently, until 
22Q               DISCOURSE  VII.

it becomes stiff, in consequence of parting with some of its
impurities.  In this state it is exposed to  the action of a
large hammer, which presses out other impurities, which is
called forging;  and the  iron is known  by the terms forged,
wrought,  or bar iron.   Of the iron so obtained, there are
also  several kinds.  One kind is known to the artists by the
term hot short iron, which is brittle when heated, but malle-
able when cold. Another kind is called cold short iron, which
possesses  qualities the reverse of the last.   If the iron be
repeatedly beat under the hammer it may  be had tolerably
pure.

   When  pure, iron is remarkable for the following proper-
ties.  Its color is a light grey : it is soft, ductile, malleable,
and  much less fusible than before purification.  Its specific
gravity  is about  7.7.   It  is distinguished from most sub-
stances, by  its being attracted by the magnet or loadstone ;
and  acquires, under various circumstances, the property of
magnetism.  This  magnetical property is particularly ac-
quired at the lower part of iron when it is kept in an elevat-
ed position. Hence, the lower ends  of shovels, pokers, &c.
are remarkably magnetic.  Instruments of iron,  struck by
lightning, and when rubbed against  each other in the same
direction, also become magnetic.   It  has been supposed,
the phenomena of magnetisrxi arise from a modification of
the  electric fluid; but the majority suppose they proceed
from a quality of the metal.

  Another property distinguishing iron is, its being soften-
ed by heat  so that  when applied  to another piece in that
state it unites, which is called welding. 
                  DISCOURSE VII.               221

                      STEEL.



  WHAT also distinguishes iron, is  its capability of uni-
ting to carbon, and forming the well known substance steel.
The method of forming steel in the manufactories is thus :
bars of soft or malleable iron are  bedded together in char-
coal and placed in a close furnace.   For six or eight  days, a
strong fire is applied.  The cementation, as it is called, is
judged of by extracting and examining  a bar occasionally.
When this appears sufficiently changed, the fire  is allowed
to decline, and the metal is taken out.  In this state it forms
blistered steel; which is afterwards rendered better by ham-
mering  it  in a forge,  or melting it into  bars, forming cast-
steel, a most invaluable article.
A NEW  METHOD OF  MAKING STEEL.
  LATELY a chemist of France, has made a  most im-
portant  improvement in the manufactory of steel,  if he can
be relied on.  His process is the following: take small pieces
of iron, and place them in a vessel, with a mixture of chalk
(carbonate  of lime) and of the earth of Hessian crucibles,
equal parts : twelve parts of this mixture are necessary for
twenty of iron.  The iron is to be covered with the mixture
to prevent  the contact of the air;  and the whole is subject-
ed to a  heat sufficient  to melt the iron for one hour. On
examination afterwards, the iron will  be found  converted
into steel, equal to that taking eight or nine days for its for-
mation in the usual way. 
222
DISCOURSE VII.
   The quantity of carbon in good steel is about one sixtieth,
according to some authors; but others state the quantity to
be less.  When the quantity is increased beyo:id this,  the
steel is rendered more brittle, in proportion to the quantity*

   Good steel is distinguished by several remarkable proper-
ties.  When  heated   and suddenly introduced into cold
water, its  hardness  is greatly  increased.   This is what i's
called  tempering  of   steel,  the  requisite hardness  being
given by attending to the degree  of heat  which the  metal
acquires, and  suffering  it to  cool accordingly.   It may
be made  so hard  as  to  scratch glass, and  is at the time
rendered more brittle and elastic.  When thus hardened,
steel may have softness  restored by heating it, and allow-
ing it to  cool gradually.   Steel may also be  distinguished
from iron,  by dropping a little  nitric acid on it, the steel is
converted to  a black color,  in consequence of the separa-
tion of its  coal or carbon; but the iron appears white.—
It is of a  light grey color;  is susceptible  of a very  fine
polish; is more fusible  than iron,  and also has a greater
specific gravity.  It is ductile and malleable,  is harder and
more elastic than any other metal, and affords sparks, when
struck against flints.   When exposed to heat, it first turns
of a straw  yellow, then of  a higher yellow, next purple,
violet, red, deep blue, and lastly bright blue, when  it  be-
comes redhot.  Steel  is called, according  to the  new no-
menclature carburet of iron.

   Iron unites to sulphur, phosphorus, and to the metals,
forming compounds possessed of  various properties which
are not very important.   It has a very strong attraction for
oxigen.  Hence, it  frequently attracts it from the atmos-
phere, and forms water  at common  temperatures,  forming
what is called the rust of iron.   When heated in contact
with  the atmospheric air,  it  unites to the oxigen more 
                  DISCOURSE VII.               223

quickly and forms scales,- if heated in contact  with water,
the water is decomposed, its hidrogen escapes  and the  ox-
igen unites to the metal: If heated in contact  with oxigen
air, the oxigen unites to it  more quickly, and much heat
and light are emitted: many of the  acids also  oxide  this
metal.  Iron is capable of  uniting to but two quantities of
oxigen;  with the first quantity,  it forms the forged scales of
iron, or more properly, black oxid of iron, which in the  100
parti contain 27 of oxigen.  If this oxid be reduced to pow-
der, and exposed to a high heat in  the open air,  it unites
to more oxigen, which converts it into a red or brown oxid of
iron,  which contains in the 100 parts 48 of oxigen. These
oxids of  iron are used as paints and occasionally  as a medi-
cine.  If heated very highly in a close vessel they part with
their oxigen, particularly if a little charcoal powder be add-
ed,  and the iron is restored to the metallic state.

   Instruments  of iron may be  prevented  from rusting, or
uniting to oxigen by the following mixture : take 8 pounds
of hog's lard, melt it with  a little water,  and add to it 4
ounces of camphor ;  when this is dissolved remove it from
the  fire  and add a little plumbago (or black  lead.)   The
iron  utensils are to be warmed very  much, and  then  the
composition is to be well rubbed on them until  they are dry.

   The  oxids  of iron unite to all the acids forming various
salts. The few which have been found of much consequence
are the following: 
224               DISCOURSE VII.

                     COPPERAS ;
                           OR
               SULPHATE OF IRON.



   THE sulphuric acid diluted with water, oxides and dis-
solves  the  iron very quickly.   The solution when evapo-
rated,  deposits the  well known article of  commerce called
copperas,  or green vitriol; but this is more properly termed
sulphate of iron.  This compound  is prepared on a  large
scale,  by burning the  iron  ores containing sulphur (called
pyrites) when exposed to the air.  The  sulphur unites to
oxigen forming sulphuric acid, which unites to the oxid of
iron forming the salt copperas,  which is washed off with
water.   In this water, old iron is added to unite to the ex-
cess of acid.   The solution is then evaporated,  and the
salt crystallizes.  It contains a considerable quantity of wa-
ter,  of which  it may be freed by heating it; and the salt
then exists in the form of a white powder.

   This powder mixed with dry nut galls, forms a  dry ink,
which several persons sell as a secret,  and which requires
only the addition of a little water to make it fit for use.
This salt is chiefly used in  the arts,  particularly in dyeing
black.
THE MURIATE  OF IRON.
  THE  muriatic  acid  also  unites  to  the  oxids of iron
forming a muriate of iron.   A preparation of  this is com- 
DISCOURSE VII.              225
 monly used as a medicine,  called flowers of steel.  If one
 pound of the muriate of ammonia (sal-ammoniac) in pow-
 der, be mixed with one ounce of steel  filings,  and if this
 be heated together in a proper vessel a compound comes
 over, which  is much used as a tonic in medicine, called
flowers of steel.
CHALYBEATE  WATERS.
  THE oxid of iron readily unites to the carbonic acid.
The common rust  of  iron contains this acid,  which it ab-
sorbs from the atmosphere.  If  a quantity  of the rust of
iron be introduced in water impregnated with carbonic acid,
the oxid of iron is dissolved, and this forms the chalybeate
waters, so generally  used as  a tonic by invalids,  when
found in springs.   The artificial combination possesses all
the virtues of that found in nature.
PRUSSIATE OF IRON;

            OR

   PRUSSIAN BLUE.
  A VERY singular mistake gave rise to the discovery of a
compound of a beautiful blue color, known in common by
the term Prussian blue.   This is formed by an oxid of iron
                         Ff 
'226
DISCOURSE  VII.
 united to an acid,  called the Prussic acid;  and in the new
 nomenclature it is termed prussiate of iron.  Mr.  Chaptal
 thus introduces this subject:

   " A chemist of Berlin being desirous of precipitating a
 decoction of cochineal with fixed alkali, borrowed of  Dip-
 pel  an alkali,  upon which he had several times distilled ani-
 mal oil.   As the decoction of  the cochineal contained sul-
 phate of iron, the liquor immediately afforded a beautiful
 blue.  The experiment being  repeated  was followed  with
 similar results ; and  this  color became an object of  com-
 merce, under the name of Prussian blue."

   " To  make Prussian blue, four  ounces of alkali are
 mixed with the same weight of dried bullock's blood, and
 the  mixture is to be exposed in a vessel to a strong heat; to
 stifle  the flame,  the  vessel is  to  be kept covered, and the
 fire is to be kept up until the mixture is converted into a red-
 hot coal. This coal is then thrown into  water which is af-
 terwards filtered,  and  evaporated considerably.  On the
 other hand two  ounces of the sulphate of  iron, and  four
 ounces of alum are dissolved in a pint of water.  The two
 solutions are mixed and  a blueish disposition falls  down,
 which is rendered  still more intensely blue, by washing it
 with muriatic acid."

   " Such is the process used in chemical laboratories, but
 in the works in the large way,  another method is followed.
 Equal parts  of raspings  of horn,  clippings  of skins or
 other animal substances are taken, and  by  means of heat,
 converted into charcoal.   Ten pounds  of  this coal  are
 mixed with  thirty pounds of potash,  and  the  mixture
is heated in an iron vessel.   After continuing twelve hours
redhot, the mixture  acquires  the  form of a soft  paste,
which  is  poured out  into  vessels of water.  The water is 
DISCOURSE  VII.
227
then filtered, and the solution mixed with another, consist-
ing of three parts of alum and  one of the sulphate of iron,
when the Prussian blue  instantly  appears  in  the form of a
precipitate."

  The celebrated Scheele was the first who shewed that the
Prussian blue contained an  acid.  This acid is called the
Prussic  acid, and it may be thus  procured.   Take two
ounces  of  powdered Prussian  blue,  and put  it in a glass
vessel, with one ounce of red precipitate and six of water.
This mixture is to be boiled for some minutes, and constantly
stirred.   It then assumes a yellow color, inclining to green.
The fluid being filtered, two ounces of boiling water are to
be thrown  on the remainder. This liquor is a Prussiate of
mercury, which  cannot be decomposed by acids or alkalies.
The solution is then poured into a bottle, in which an ounce
of newly made  filings of iron  are put.   A  little sulphuric
acid is then to be added, and the whole  agitated for  some
minutes.   The mixture becomes perfectly black, by the re-
duction of the mercury.  After suffering it to rest for some
time, the liquid is  decanted, put into a retort,  and distill-
ed,  by a gentle fire.   The  operation must be discontinued
when one quarter of the fluid passes over.  As this product
contains a  small quantity of sulphuric acid, it should be in-
troduced in another retort with a little chalk, and be distilled
by a very gentle fire.  The Prussic acid then comes over in
a state of the greatest purity.  It has a particular smell and
a sweet taste.  Its  exact composition is not known, but sus-
picions have arisen  that it does not owe  its acid properties
to oxigen.

   The Prussic acid has a very  strong attraction for the ox-
 id of iron, and in consequence  of forming with it a blue
 compound, it answers as an excellent test to detect the pre-
 sence of iron in any fluid.   If lime water be digested up- 
223
DISCOURSE  VII.
on Prussian blue,  the color is lost, and the water  acquires
a yellow color.  This is a prussiate of  lime, and answers
very well to detect the presence of iron.  Ammonia by
means of heat destroys the  color  of  the Prussian  blue,
and also the  pure fixed alkalies, potash and soda.

  Prussian blue has also been found in  the earth in  small
quantity.  It is an article much used in the art of dyeing.

  The uses  of iron are so important, that they are too ge-
nerally known, to  need dwelling on in this  place.   The
happiness and power of nations materially depend  upon
this metal.  It has been considered  as the soul of  the arts.
Under the form of cast iron,  it serves  to  construct many
machines and utensils.   In bar iron, it answers for  many
purposes : it unites force  and resistance to flexibility and
elasticity.  In the state  of steel, it is fitted for the largest
machinery,  and  also  for  the most delicate instruments.—
Its capability of acquiring the  magnetic power, has  given
birth  to  the mariner s compass,  which has given inexhaust-
ible sources of industry and wealth to the  world.   Besides
these, as before remarked, it is used in the healing art, and
in the arts of dyeing and painting.
dftyfo
^jp 
DISCOURSE VIII
SEVENTH  METAL.
                        TIN.


  THIS metal  is found comparatively in but small quanti-
ties.  It is met with in greatest abundance in Cornwall in
England, and in lesser quantities in the mines of Bohe-
mia, Saxony, the island of Benca, and in the East Indies.
It is also found in Chili, and  Mexico in  South  America.
It exists only  in a  state  of  combination with oxigen, it
forms an ore of a white or dark brown color, and with sul-
phur it forms the ore called tin pyrites.

  To extract the metal from its ores, it  should be heated
in the air,  so that the volatile parts may escape.   It should
then be  mixed  with charcoal  powder, and  exposed to  a
pretty  strong heat in a furnace.  It melts  at about 420°
Fahrenheit, and may then be allowed to run off. 
230
DISCOURSE  VIII.
  Pure tin is of a brilliant white color, though not so white
as silver ; it is one of the most fusible metals,  and  also the
lightest;  its specific gravity not exceeding 7 :299 after ham-
mering.  By an intense heat it is volatilized. It easily bends,
and makes a noise called the crackling of tin.  It is exceedingly
soft  and ductile, and may  be  hammered into  leaves not
thicker than one thousandth of an inch.  It has  scarcely any
sound  when struck against hard bodies.  It resists  the action
of the air.   It unites to  sulphur and also to the metals, for-
ming some useful alloys.

   About one thirty-seventh  of  tin scarcely alters the pro-
perties of gold; but  a  larger quantity  renders it brittle,
and  changes its color.   With silver and  platina,  it forms
alloys  of no importance.  It readily  unites to mercury in
any  proportion.  If one part of zinc and tin be  melted to-
gether and mixed  and agitated together in a wooden box,
with two parts of mercury, a powder will be formed  which
is applied to electrical machines,  with the  effect of increas-
ing considerably  their power of collecting electricity.
                LOOKING  GLASSES.

  ARE silvered on one side, or covered over with a prepa-
ration  which reflects the light, by an alloy of tin and mer-
cury.   For this  purpose, tin foil is smoothly placed on a
flat stone  or table,  and mercury, in  which some tin has al-
ready been dissolved, is poured upon it, and spread with a
feather or brush of cloth, until it has united to every part.
A plate of glass is then cautiously slid upon it from one end
to the other end,  in such a manner that part of the unneces-
sary mercury is driven off, before its  edge.   The remainder 
DISCOURSE VIII.              231
has united to the tin.   The glass is then loaded with weights
all over, so as to press out still more of the mercury, which
runs off by inclining the table  towards a side.    In a few
hours the union between the glass and alloy is completed,
and the weights may be removed.   In the small way, about
two  ounces  of mercury are requisite for -covering three
square feet of glass.
TINNING OF  IRON.
   IRON is tinned in the following manner : Plates of iron,
 properly thinned, are immersed in water, acidulated with a
little  sulphuric or muriatic acids,  in order  to free them
completely from rust;  they are then scoured bright,  and
placed in a pot filled with melted tin,  the surface of which
is covered with suet, or pitch, to prevent the surface of the
tin from oxiding.  The plates of iron  being then suffered
to pass through it, the tin will unite with them,  so  as to
cover each side of the plate with a  thin white coat,  con-
stituting what are called tin plates.   In  the same way stir-
rups, buckles, bridle bits, &c. are covered with coats of  tin.



           TINNING COPPER,  VESSELS.
  VESSELS of copper, when used for cooking,  are com-
monly covered with a thin coat of tin, to prevent the copper
from uniting to oxigen, and dissolving in the food, so as to 
232
DISCOURSE  Vllh
render it poisonous.    These vessels are said  to be tinned.
To do this, their interior surface is scraped clean with an
iron instrument, and rubbed over with sal-ammoniac, (mu-
riate of ammonia.)  The vessel is then heated, and a little
pitch  thrown  in  it and allowed to spread  on  the surface.
Then  a bit of tin is applied over the hot copper,  which  in-
stantly assumes a silvery whiteness.  The object of the first
steps is to have the copper free from all rust, as the tin will
not unite to the oxid of the metal.   The coat of tin so ap-
plied is exceedingly thin.  Not more than twenty-five grains
of tin are necessary for tinning a copper bason one foot  in
diameter ; and it is useless to make  the coat thicker, as the
tin melts and runs off when the vessel is heated.

   The other  alloys  of tin have not been found of  im-
portance.
OXIDS OF  TIN.
  TIN unites to oxigen in different  quantities.  If tin be
melted in a ladle exposed to atmospheric air, a grey cover-
ing will appear, which forms wrinkles : when this is  taken
off, it is  soon succeeded by another, and  in this manner
the whole metal may be converted into  a powder, which
is an oxid of tin of a grey or yellow  color.  It  is this oxid
of tin which the makers of pewter spoons and plates who
usually travel over the country,  call the dross of  tin.   They
are  very  careful to skim the  metal while fluid as often as
posssible, to clear it of the dross, and by this means they
avoid giving those  who employ them  any  more of the old
pewter than that which they cannot  contrive to carry off- 
                  DISCOURSE VIII.               233

This pretended dross they readily convert into good tin, by
heating it in closed vessels in contact with charcoal powder.

   If this oxid of tin be exposed to a strong heat in an open
vessel,  and be stirred up repeatedly, it unites to more oxi-
gen and appears of a white color.  This is white oxid of tin,
commonly  called putty of tin.   It is used for polishing glass
fortellescopes,  marble,  steel, &c.  United to glass, it de-
prives  it of its transparency, and renders it like white en-
amel.   This oxid of tin may also be prepared by heating
tin in contact with nitric acid, when a violent action ensues
and the whole of  the tin is converted into a white powder,
or the  oxid of  tin.  If a little water and potash be added
to the tin with the nitric acid, then the hidrogen of the wa-
ter,  and the nitrogen of  the acid unite and form ammonia.


   This white oxid of tin by fusion, unites to sulphur and
forms  the auruni musivum, more properly called yellow sul-
phurated oxid of  tin, an article much used to give a beau-
tiful color  to bronze, to increase the strength of electrical
machines ; and it is employed by japanners,  for many arti-
cles intended to have the appearance of  metallic gold.  The
process to form it is thus : twelve parts of tin are melted in a
vessel  by a brisk fire, and three of mercury are then added
to it.  This mass is to be reduced to powder  in a stone mor-
tar, and then very well rubbed up with  seven parts of sul-
phur and three of sal-ammoniac.  The mixture is to be ex-
posed to heat as  long as any white vapors are  disengaged ;
the heat is then moderately increased,  and at the bottom of
the vessel the aurum musivum remains,  w:th a little sulphu-
ret of mercury and muriate of  tin.  If the heat have been
 too strong, only the black sulphuret of tin remains.
Gg 
234
DISCOURSE  VIII.
  The action of acids upon tin varies according to the  de-
gree of purity of the  metal.   The oxides of the metal
unite very readily to the acids.

  The sulphuric acid dissolves tin by the assistance of heat;
but a  part of the acid is decomposed, and flies off in the
form of sulphureous acid.

   The muriatic acid dissolves tin, whether cold or heated;
at the same time  emitting a very fetid air.   The solution is
yellowish, and affords crystals of the muriate of tin by evapo-
ration.  The oxi-muriatic acid oxides, and dissolves this
 metal much more  speedily.   The liquor known by the
 name of the fuming liquor of Liiavius, appears to be an
 oxi-muriate of tin   To make this  preparation, tin  is al-
 loyed with one fifth of mercury, and this alloy in powder
 is mixed with an equal weight of corrosive sublimate.   The
 whole is then put in a retort,  a  receiver adapted,  and dis-
 tillation proceeded upon, by applying a gentle heat   An
 insipid liquor passes over first, which is followed  by a sud-
 den eruption of  white vapors, which condense into  a
 transparent liquor, that emits a  considerable quantity of
 vapors by mere exposure to the air.

    Tin when dissolved in the riitro-muriatic acid is  used
 for the  formation  of a composition to dye scarlet.  The
 common aqua fortis  of the  shops is commonly employed
 instead"of the above acid properly made.   In  consequence
 of the composition'of  aqua  fortis varying, the  dyers fre-
 quently complain,  that the aqua  fortis precipitates; Which
 happens When it contains too small  a quantity of muriatic
 acid; or that the color is obscure, which happens when the
 nitric acid is too small in quantity.   The first inconvenience
 is remedied,  by dissolving common salt,  or sal-ammoniac
 in the aqua  fortis; and the Second  by adding nitre.   The 
DISCOURSE  VIII.
235
most  accurate proportions for rnaking a good solvent for
tin are two parts of nitric and one of muriatic acid.

  Most of the tin in commerce  is alloyed with other me-
tals.   That of England contains copper and arsenic.

  When tin contains arsenic, the solution in  the muriatic
acid  exhibits a black  powder, which consists of arsenic
separated from tin.  This method is capable of rendering
the two thousandth part of arsenic in tin perceptible.

  If the tin contain copper, the muriatic acid, which attacks
tin with facility,  precipitates the copper in the form of a
grey powder.  The copper  may  likewise be  precipitated,
if  a plate of tin.be immersed in a solution of the alloy.

  In order to ascertain  the presence  of lead in  tin, the
nitric acid must be poured on it—the acid dissolves the lead,
and leaves the  tin in the form of a white powder.   And
the lead may be detected in the acid.
EIGHTH  METAL.
                        LEAD.

  This metal is found in large quantities in many parts of the
earth, generally mineralized with oxigen, and sulphuric, car-
bonic and phosphoric acids. The largest quantities are found
united to sulphur, forming the ore called gafea, which feels
greasy and has a hlueish lead grey.  The following  are the 
236
DISCOURSE  VIII.
names of the different ores,  in  which this metal has been
found:

          1 Galena,
          2 Blue lead ore,
          3 Black lead ore,
          4 Earthy ore of lead,
          5 Carbonate of lead, or white lead,
          6 Sulphate of  lead,
          7 Phosphate of lead,
          8 Chromate of lead,
          9 Molydate of lead,
         10  Arseniate of lead.

   Besides several others useless to mention.

   To separate lead from its ores it is first exposed to heat,
 which carries off the volatile parts.  It is then introduced
 in a furnace  in contact  with the burning fuel,  where  it
 melts, and may be  drawn off from the bottom.  In  this
 state it commonly contains a little silver.  To free it from
 this it is introduced in a refining furnace and melted.  Here
 a quantity of fresh air is applied to the surface of the  lead
 by means of a large bellows.  This  oxides the  lead and
 converts it into the yellow scaly oxid,  which is driven  off
 from the silver that remains pure in the furnace.   This
 oxid is then to be melted in  contact with powdered char-
 coal, when  it  parts with its oxigen, and the lead falls at
 the bottom in a pure state.

   Lead  is of a blueish white color when first cut;  but it
 soon tarnishes on exposure to the air.  It is among the
 softest and least elastic metals.  It is malleable and ductile,
 but not in a very great degree. Its specific gravity is 11.435.
 Jt unites to  sulphur  and phosphorus;  forming,  however* 
DISCOURSE  VIII.
237
no useful  compounds.  It melts at 540°  Fahrenheit, and
renders other metals more fusible.

  When exposed to the  air, lead slowly unites to oxigen,
forms  a grey powder, which afterwards becomes white.
This union with oxigen, may be much hastened, if the me-
tal be heated.  If the lead be melted and stirred up in con-
tact with air, it readily unites to oxigen, and appears in the
form of a  grey powder, which then assumes a lively yellow
color, forming the pigment called massicot; and if the heat
be continued, this massicot absorbs more oxigen and as-
sumes a red color.  It is then called minimum, or red lead.
If this be  melted it parts with some oxigen, and is convert-
ed into lytharge.  The red oxid of lead contains  in the 100
parts,  12 of oxigen, which it will give up as all the rest of
the metallic oxids if heated in  a  retort, particularly in con-
tact with  coal   The preparations of lead are used as paints
when mixed with oils  On account of their  fusibility, they
are used in glass houses, to assist the fusion of the glass; to
render the glass softer, heavier and more  susceptibe  of be-
ing  cut and polished.   These  oxids of  lead are likewise
used to harden oils, or to render  them more drying by boil-
ing the oils over them.  In this operation,  they part with
their oxigen which unites to the  oils.

   The oxids of lead readily unite to the acids, forming com-
 pounds, most of which are of  no importance.   The most
 remarkable are, the

                 SUGAR OF  LEAD;
                           OR
              ACETATE  OF  LEAD.

   IF vinegar, which owes its  acidity to the  acetic acid, be
 poured on the oxids of lead, the acid unites to the oxid and 
238              DISCOURSE VIII.
forms the sugar of lead;  which is used as a medicine, m
small doses of 2 or 6 grains, and also in applications to al-
lay inflammation.




                  WHITE  LEAD;
                         OR

             CARBONATE OF LEAD.
  THE white lead of commerce is formed by allowing the
steam of vinegar to pass through thin sheets of lead.  The
lead is oxided,  and unites to carbonic acid, forming a white
powder, which should be dried.  This is used as a paint*
and as putty.   It is a carbonate of lead.
     MURIATE OF LEAD;
               OR

PATENT LONDON YELLOW.
  THIS compound which has  lately been much used as a
paint, is thus formed:  Four parts of litharge,  and one of
Common salt, (muriate of soda) are to be rubbed up together
and wetted sufficiently with water to form a paste. The mu-
riatic acid then unites to the oxid of'lead, and the soda is left
in a free state.  The muriate of lead is to be exposed to a
moderate heat, when it becomes fit for use* 
DISCOURSE VIII.
239
SULPHATE  OF LEAD.
   THE  sulphuric acid has a remarkably strong attraction
for lead,  and attracts it from all the rest of its combina-
tions, forming with it an insoluble compound.  Hence it is
a good test, hy  which the presence  of lead in fluids may
be detected.  The other compounds  of the  oxids of lead
with the acids have not been much examined.


   Lead  unites to other metals,  forming  various alloys.
When combined With copper,  it is used for making the
largest types for printing.  Three parts of tin and one of
lead form an alloy called ley  penvter, which is harder than
tin.   Tin-foil is generally  composed of  two parts of lead
and one of tin.  This being more  fusible  than  either of
the metals separately,  it is used to connect different metals
together, or as a solder.

   Lead in the metallic state is used to make water pipes, to
line tea chests, to form bullets and shot, &c.   Shot are usu-
ally formed by melring lead with  a little arsenic, which
renders  it more brittle; it  is then poured into a  sieve,
which has round orifices  in it, and  which stands over wa-
ter.  The lead assumes the round form as it enters the
water. 
DISCOURSE VIli:

NINTH METAL.
                        ZINC


  ZINC is found in nature confined with oxigen, carbonit
acid,  sulphuric acid,  and with sulphur.  With  oxigen it
forms  the ore  called calamine,  or  lapis calaminaris, of a
grey,  white, yellow or brown color.  The most abundant
ore is that called blende, in which the zinc is united to sul-
phur : This is of various colors, brown, yellow, hyacinth,
black, &c. and with various  degrees of lustre.

  In order to obtain zinc from its ores,  they must  first be
roasted (or heated exposed to  air)  and then mixt with half
their weight of charcoal in an earthen retort, connected at
its end with water.   On applying  heat, and increasing it
for some time, the zinc melts and sublimes, and is found
deposited at the neck of the vessel.

  Zinc may be distinguished by the following properties :
It is of a brilliant white color, with a blueish tint.  It pos-
sesses some degree of ductility, and may be extended when
carefully pressed.   It is a very strong conductor of  galvan-
ism.   Its specific gravity is 7  190 : It melts at 700° Fahren-
heit, and by an increase of heat, it is volatilized unchanged.
It undergoes very little alteration from exposure to atmos-
pheric air ;  nor is it changed by water, unless the tempera-
ture be high,  in which  case the decomposition of the water
is rapid; its oxigen unites to the  zinc  and the  hidrogen
escapes in the form of  air..   It has  a very strong  attraction
for oxigen.   When heated  it  burns with a very bright
240 
DISCOURSE VIII.              wi
flame and flakes of exceedingly white and light  matter, like
cotton, will rise at the same time.    This is the white oxid
of zinc,  which  is called, commonly, philosophical wool,
pompholix, or nihil album.   This oxide may be fused into
a kind of glass, of a beautiful yellow color, by means of a
violent heat.

  The attraction of zinc for oxigen is so strong that most
of the metallic solutions are decomposed, when zinc is add-
ed to them.   We have an example  in the lead tree.   This
is formed by dissolving one part of the sugar of lead in 35
or 40 of distilled water, and suspending a bit of zinc in the
middle of a  glass bottle containing it.  The zinc attracts
the oxigen of the  sugar of lead (acetate of lead) and is dis-
solved, while the lead is  gradually deposited on the zinc, of
a moss-like appearance and metallic splendor, which some?
times has the shape of a tree.


                NITRATE OF ZINC.


  THE nitric acid diluted  rapidly, oxides zinc,  and then
dissolves it; nitrous gas being emitted.   The solution, if
evaporated, yields crystals of the  nitrate of  zinc, which has
not been found of much consequence.


                 WHITE VITRIOL;
                           OR
            THE SULPHATE OF ZINC,


   THIS salt is formed by the union of sulphuric  acid with
 zinc.  If the diluted sulphuric acid be added to  zinc, the
                          h h 
242
DISCOURSE vin.
water is rapidly decomposed ; its hidrogen escapes in the
form of air, while its oxigen unites to zinc, forming an oxid,
which then unites to the  acid and is  dissolved.  The solu-
tion, if evaporated, will yield the white vitriol of the shops,
an article much  used to allay inflammations, when dissolved
in water and applied to the inflamed parts.   In doses of
twenty  or thirty grains it is a quick emetic.   This is the
only preparation of zinc  with an acid, which has been much
attended to.

   For the purposes of commerce, it is made by the decom-
 position of the ore blende, which is composed of sulphur and
 zinc.   The ore is  heated  and thrown into cisterns of wa-
 ter, where it is left for twenty-four hours.   The roasted
 mineral is three times extinguished in the same water; after
 which the water is evaporated and put into coolers.   At the
 end of fifteen days the water is decanted, in order to sepa-
 rate the crystals of the sulphate of zinc.   These crystals are
 afterwards fused in iron vessels,  ard the liquor  is poured
 into coolers, where it is stirred till it congeals.

    Zinc unites  to  other metals,  forming alloys  which are
 very useful, and which were mentioned while considering
 sopper and tin.
TENTH METAL.
                     BISMUTH.

  THIS is  a metal not  found in great quantities, or of
much consequence.  It  is generally found in die metallic 
DISCOURSE VIII.
24.3
state, and is procured from the mines of Saxony, Sweden,
&c.   To obtain the metal in a state of purity, it is only
necessary to expose the ore to a strong heat, in a closed
retort.   The metal sublimes,  and may be  taken from the
neck of the retort.

  Bismuth is of a reddish white color,  is destitute of taste
and  smell,  is possessed of but little ductility or malleabi-
lity,  and is soft enough to be cut with  the knife.   Its spe-
cific gravity is 9.800.  It is brittle,  and can readily be re-
duced to small pieces.  It melts at a temperature of 460°
and  in a higher heat is volatilized.   If  heated, exposed  to
the  air,  it readily unites to oxigen,  forming  a  white oxid
of bismuth.   This oxid unites to the acids, forming com'
pounds of no known value.  The oxid is prepared by pour-
ing the nitric acid on the  metal, which  oxides and dissolves
it.   Then, if  the solution be diluted with water, the oxid
of bismuth falls to the bottom, in the form of  a beautiful
white powder,  which was formerly much used to whiten
the skin.   But whenever  it comes in contact  with the fetid
airs,  it  turns of a  black  color.   It is  used in pomatum to
blacken the hair.   When this oxid  is dissolved in an acid,
it may be used as a sympathetic  ink.   On writing with it
on paper, the characters  will  only  appear when the paper
is held over the vapor arising from  moistened sulphuret of
potash.

   Bismuth unites to most of the met ils, forming various
allovs.   When fused with gold, the alloy  retains the color
of the bismuth, and is brittle.  This metal when united t<9
silver does not render it so brittle as gold.   It  diminishes
the red  color of copper, but is deprived of  its own color
by uniting with lead, and the alloy appears of  a dark grey
color.  When bismuth is mixed with a small portion of tin,
it wives it a greater degree of brilliancy and hardness.  It is 
244
DISCOURSE VIII.
remarkable,  that a mixture of eight parts of bismuth, five
of lead,  and three of  tin, is so fusible that it  remains
fluid in boiling water.

   Bismuth unites to mercury and forms a fluid alloy, a cir-
cumstance  which  has led some unprincipled druggists to
mix it  with that metal.  The fraud may be known,  as the
mercury  does not  appear quite as fluid as when pure.  It
may also be  detected,  by dissolving the mixture in nitric
acid ; and on adding water the bismuth will be precipitated.
ELEVENTH  METAL.
                    ANTIMONY.

  THIS is one of the most noted metals which has excited
a great deal  of  attention,  particularly among the  alche-
mists,  who called it sacred lead, radical principle of metals,
Sec   It is the base of the numerous medicines in the shops,
called antimonial.

  Antimony is but  rarely if  ever found  native.   Various
ores containing it are found in Germany, Hungary, France,
Spain, Britain, Sweden, Norway, &c.  They are generally
blended with various silicious earths.  The most remarkable
ores are:

         1  Grey ore of  antimony.'
         2  White  oxid of antimony.
         3  Red oxid of antimony.
         4  Arseniate of antimony. 
DISCOURSE  VIII.
245
  But by far the most abundant ore is the grey ore of anti-
mony, in  which the metal exists  united to  sulphur.  This
ore  is heated in a proper place, and the combination of sul-
phur and antimony, being very fusible, the compound readily
runs out at the bottom.  This compound is called crude an-
timony, in common, and was supposed at one time to be the
pure  metal.   Two methods are  practised  to separate the
sulphur from this crude antimony, or sulphuret of antimony.

  The first method is by the  slow and gradual oxidation of
the metal, in which case, a grey oxid is formed.  This grey
oxid,  urged by a violent heat,  melts and forms the glass of an-
timony, which when the fusion  is complete  is transparent.
This-glass of antimony,  when bedded in charcoal and heat-
ed most intensely hot, parts with its oxigen, and leaves the
antimony in a state of purity.

  The second  method  of obtaining the metal from crude
antimony,  consists in  heating it in a proper vessel,  by ad-
ding  to eight parts of it six of tartar, and  three of nitre.
This  mixture is then kept in a  high  heat till the antimony
melts.  Or if  the crude antimony be heated  with  copper,
silver or iron,  its sulphur unites to these  metals,  and the
antimony  remains pure.

  Antimony is of a greyish  white color,  having  a slight
blueish shade, and very brilliant.  It is very brittle,  and ap-
pears to be composed of a number of very small plates.  Its
specific gravity is 6.702.  It  is  the lightest, and among the
hardest and  most infusible metals.   It  decomposes water
very  readily.

   This metal unites to others, forming alloys possessed of
 various properties, but most of them are of no  use.  The
 most valuable is that formed for  printers' types, which are 
246
DISCOURSE VIII.
composed commonly of ten parts of lead, and one of an-
timony, to which a little zinc and bismuth are sometimes
added.

   Antimony unites  to  oxigen in  different  proportions.
When fused and exposed to the air, it  emits white fumes,
known by the name of argentine snow, or flowers of antimo-
ny.  These fumes are partially soluble in water, to winch
they impart emetic qualities.

   When  this metal is reduced to powder and exposed to a
dull red heat, in an open vessel, oxigen is absorbed, and a
grey oxid of antimony is formed.   And if this grey oxid be ex-
posed to a still higher heat, larger quantities of oxigen com-
bine with it, and the product is a white oxid of antimony.  If
this white oxid of antimony be  exposed  to a still stronger
heat, it fuses and forms  a nitrous oxid  of antimony, com-
monly called glass of antimony.   This  compound is much
 used as a medicine.  It is possessed of very corrosive pro-
 perties.   But when rubbed up with wax,  which is after^
 wards burnt off, this corrosive property is lessened.  It then
 constitutes the cerated glass of  antimony,  so  much used  in
 dysenteric affections.

   The glass of antimony is used in the preparation called
 antimonial wine.  For this purpose, nothing more is neces-
 sary than to add a little of it to a bottle of wine.  The wine
 dissolves it in proportion to its acid; and hence the strength
 of  antimonial wine varies very much,  as do the acids  of
 wines. 
DE3COURSE VIII.
247
             TARTAR  EMETIC,
                      OR

ANTIMONIATED TARTRITE OF POTASH.
  THE preparation commonly called tartar, or tartar emetic,
is made of this  glass of antimony and common cream of
tartar.  The method of making it is not the same among
different apothecaries: hence the properties of tartar emetic
are found to vary so much.  The best method of  making
it is stated to be the following:

  Take very transparent glass  of antimony, grind it very
fine  and  boil it in water,  with an equal  weight  of  the
cream of tartar.   Then filter the fluid and evaporate it by
a gentle  heat.  When it is then  allowed to rest,  crystals
of tartar emetic  will  be deposited.  These will  operate
very well in doses of from one to four grains.   This com-
pound is  termed in the new nomenclature antimoniated tar-
trite of potash.
 BUTTER OF ANTIMONY;
              OR
MURIATE OF ANTIMONY.
  THE muriatic acid acts upon antimony, but slowly.  But
if two parts of corrosive sublimate  (oxi-muriate of mercu-
ry) and one of antimony, be distilled together, a very slight
degree of heat drives over a matter which is called butter of 
^48              DISCOURSE VIII.
antimony.   By a very moderate heat, this may be rendered
fluid, and in consequence, may readily be poured from one
vessel to another.   This preparation i<" used sometimes to
corrode animal parts.    When diluted with water, a white
powder falls down, which is a pure oxid  of antimony.  It
is generally called powder of algaroth.
NITRATE OF ANTIMONY.
  THE nitric acid is  decomposed upon  this metal with
great facility.  It oxides a considerable part and dissolves a
small portion,  which is suspended in the fluid, and may be
crystallized by evaporation.   The oxide remaining, is very
white, and is called bezoar mineral.
JAMES' POWDER.
  The phosphoric acid also unites  to an oxid of antimony
and forms  a celebrated febrifuge  powder, called  James'
powder.  The exact  composition  of this medicine is not
generally known,  and consequently it is chiefly  prepared
by a few apothecaries in England.   Its dose is from 5 to 10
grains.

  The alkalies do not  sensibly act upon  antimony,  but
when  combined with sulphur they  operate very readily.
This has led to the preparation of a very valuable medicine,
called 
DISCOURSE VIII.             249
               KERMES' MINERAL;
                          OR
      GOLDEN SULPHUR OF ANTIMONY.

  THIS medicine may be made by boiling ten or twelve
parts of a pure alkaline solution,  with two pounds of the
crude or sulphuret of antimony.   The boiling is continued
for half an hour, after which the fluid is filtered, and much
of the medicine falls to the bottom on cooling.   Fresh al-
kali may be digested, until the whole of the antimony is
consumed.   This preparation has somewhat of an orange
color.  It is termed by the chemists  hidro-sulphuret of anti-
mony.   In doses of from one to   five  grains, it  is given to
adults to promote perspiration.  It sometimes operates  as
an emetic.   In  doses of about one ounce it is given  to
horses.

  Besides the above preparations of antimony, the metal is
given in the form of a pill, in the  metallic  state.  It ap-
pears to be soluble in the stomach, in small quantities, and
excites slight purging.  This was called the perpetual pill,
as it was frequently kept  for ages  in families, who after
taking and voiding it, preserved it for further use.
TWELFTH METAL.
                     ARSENIC.

  THE substance which is  sold  in commerce under tfifes
name of arsenic, is a metallic oxide of a glittering white-
                         Ii 
250
DISCOURSE  VIII.
ness, sometimes of a vitreous appearance; exciting the im-
pression of an acid taste on the tongue; volatile when ex-
posed to the  fire, in which  situation it rises in the form of
a white fume, with a very evident smell of garlic.

   This metal is scattered in great abundance over the mine-
 ral kingdom.  It is found in black heavy  masses of little
 brilliancy, called native arsenic, in different parts of Ger-
 many.   Mineralized by sulphur, it forms two ores which
 are met with about mount Vesuvius ;  the one is of a yel-
 low color called orpiment,  the  other has a red appearance
 and  is termed  realgar; this last contains  most sulphur.
 This metal is also found alloyed with cobalt,  antimony, tin,
 copper, iron,  and other metals.  When united to oxigen
 it forms native oxid of antimony, which is found of an earthy
 appearance, and of  a whitish grey color.

    Arsenic is usually extracted from the ore containing oxi-
  gen.   It is introduced in a tightly closed  vessel with char-
  coal' powder and  a  little potash, and then  heat  is applied.
  The arsenic sublimes and  adheres to the top of  the vessel,
  from which it is to be taken and preserved under water.

    This metal is very brittle, and if recently broke, its color
  is between tin white and lead grey; but on exposure to air,
  it soon loses its metallic lustre, and turns at last dull and of
  a black appearance.   Its specific gravity is about 8.000. It
   is entirely volatilized when heated to 356° Fahrenheit, so
   that it readily sublimes.   It readily unites to oxigen and to
   various metals, and it is to most animals a deadly poison.

     If arsenic be heated, while exposed to atmospheric air it
   readily burns, and when made redhot, it burns with a blue
   flame and emits  fumes of a garlic smell,  by which fumes
   and smell  the presence  of the metal  in  any compound 
DISCOURSE VIIL
thrown in the  fire  may  frequently be detected.  These
fumes are a compound  of arsenic and  oxigen, which may
readily be condensed;  and they  then  constitute what is
commonly called arsenic.   This oxid of arsenic may be vo-
latilized :  it has  a sharp caustic taste, and is soluble in wa-
ter.   It is capable of uniting to an additional quantity of ox-
igen, forming a compound possessed of all the  properties
of acids, and called arsenic acid.  This  acid unites to the al-
kalies, earths, and metallic oxids,  forming compounds cal-
led arseniates, which have not yet been  found of conse-
quence.

  Arsenic unites to  copper forming a white alloy.  By this
the presence of the metal  may readily be detected in most
instances.  If the substance supposed to contain the metal
be placed between two bright  copper plates, bound  to-
gether  by  wire and excluded from the  air entirely, and
then exposed to a strong heat the arsenic unites to the copper
and turns it of a white  appearance as may be seen on exa-
mination after the whole is cooled.

   Arsenic is used by the dyers : it is a component part of
some glazes, and in the  state of realgar and orpiment it is
much used in painting.  In small doses, commencing with
one sixteenth of a grain and gradually increasing the quan-
tity it i given with great success in cases of  cancer and in-
termittent fever.   Mr. Chaptal concludes this  subject with
the following judicious remarks :

   " This metal, which is very abundant, and very frequent-
ly met with in mines, causes the destruction of a number of
workmen who explore them.  Being very volatile, it forms
a dust which affects and  destroys the lungs; and the unhap-
py miners, after  a languishing  life of a few years, all perish
sooner or later.  The property  which it possesses,  of  being 
252
DISCOURSE VIII.
soluble in water, multiplies  and facilitates  its destructive
power ; and it ought to be proscribed in commerce, by the
strict law which prohibits the sale  of  poison to unknown
persons.   Arsenic is every day  the instrument by which
victims  are sacrificed, either by  die hand of wickedness or
imprudence.   It is often mistaken for sugar ; and these mis-
takes are attended with  the most dreadful consequences.
Whenever there is the least reason to suspect its presence,
the doubt may be cleared up by throwing a small quantity of
the powder upon heated coals.  The white  fumes, and the
smell of garlic, are indications  of  the presence of arsenic.
The  symptoms which characterize this poison are, a great
constriction  of the throat, the teeth set on edge, and the
mouth  strongly heated; an  involuntary spitting,  with ex-
treme pains in the stomach, vomiting of glairous and bloody
matter, with cold sweats and convulsions.

   " Mucilaginous drinks have been long ago given to per-
sons poisoned by arsenic.   Milk, fat, oils, butter, &c. have
been much employed.   Mr. Navier has proposed  a  more
direct counterpoison.   He  prescribes one dram  of  sul-
phur of potash,  or liver of sulphur, to  be  dissolved in a
pint of water, which the patient is directed to drink at se-
veral draughts.   The sulphur unites to the arsenic, and de^
stroys its causticity.   When the first symptoms are  dissi-
pated,  he advises  the use of mineral sulphureous waters.
 He likewise approves of milk.  Vinegar,  which dissolve?
 arsenic, has likewise been recommended by Mr. Sage." 
DISCOURSE  VIII.
253
THIRTEENTH METAL.
                    MANGANESE.

  THIS metallic substance  seems,  after  iron, to be the
most frequently diffused metal through the earth.  Its ores
are very common.   It is always found united to oxigen, in
different quantities.  These oxids are distinguished by their
color,  there being one species,  called the grey oxid of man-
ganese ; then there is the reddish white oxid,  and the car-
bonate of manganese.   All these combinations have an earthy
texture, and  are   heavy, and   generally  contain  consi-
derable quantities  of  iron.    Their color  is  sometimes
black,  grey, and seldom white.   The article sold by potters
under  the name of  manganese,  is  an oxid  of manganese.
Dr. Woodhouse of Philadelphia  states, that great quantities
of  it may be obtained in this country on the Leheigh river.
 A  portion which he analyzed, that was brought from  that
place*  was found of very good quality.

   This metal may be obtained in a state of purity by mix-
ing the oxid, finely powdered, with the charcoal, and expos-
ing the whole to a very intense heat in a retort.  The oxigen
unites to the coal and escapes in the  form of fixed air, leav-
ing the metal in a tolerable state of purity in the retort.

'*  Manganese is of a whitish grey color, and when broken
has a very irregular appearance.   It soon loses its lustre
when  exposed to  the  air.  Its specific gravity is about
 6.850.  It is very hard and brittle.   It is the most difficult
 metal  to fuse, next to platina.   Its attraction for oxigen is
 so strong, that in a low temperature it attracts it from the 
254
DISCOURSE  VIII.
atmosphere, and consequently can only be kept pure under
oil or water.  It is the most combustible metal;  it unites
to different quantities of oxigen, and the color of the oxid
depends on the quantity.   It unites to other metals, forming
alloys of no value.

  The sulphuric acid unites- to  manganese  very readily.
When the  metal is in its  common state, that is united  to
great quantities  of oxigen, on putting it  in a retort with
sulphuric acid and applying a gentle heat, great quantities
of oxigen air will come  over  in a state of purity.   Dr.
Woodhouse in a  paper in  the Medical Repository recom-
mends this method of obtaining oxigen air very strongly ;
and  Chaptal states, that  he procured  more than five pints
of pure air from one ounce of  the metalic oxid, by means
of the sulphuric acid.   It seems  that the metal contains
too great a portion  of oxigen in  its usual  state to unite to
the sulphuric acid, and consequently  it parts with oxigen
when the acid is added to it, and only retains a small quantity,
with which it combines to the acid forming the sulphate of
manganese.  This sulphate of manganese is soluble in wa-
ter and by evaporation may be made to crystallize.   It has
not been found of use.

  The nitric acid dissolves manganese with effervescence.
The solution of  the nitrate of manganese has  frequently a
dull color, and assumes a red color with difficulty.   This
solution does not afford crystals.

   The muriatic  acid dissolves manganese; but  when the
acid is poured on the common  oxid, the oxi-muriatic acid,
of which we have treated,  is formed.   In  consequence  of
this, the  metal  is frequently employed in this manner,  to
yield the above air, which is coming into great demand. 
DISCOURSE VIII.
255
  The carbonic acid  unites to the common oxid of manga- '
nese.   Indeed the manganese of potters  contain considera-
ble  quantities of this air.   Hence on heating it in a retort,
to obtain oxigen air, a considerable quantity  of carbonic a-
cid comes over.  All the other acids combine with this me-
tal ; but they do not form compounds of known value.

  Manganese is precipitated from its solutions by the alka-
lies, in the form of a whitish, gelatinous matter;  but this
precipitate soon loses  its color, and becomes black on the
contact of the atmosphere.   This arises in consequence of
the absorption of oxigen air.   Mr.  Chaptal, on observing
this, proposed to employ this precipitate in the construction
of an eudiometer, on the same principle that the sulphuret
of potash is  used.   The diminution of a  given bulk of air
in  its  presence, would indicate the quantity of air which
had been present.

   In the arts the black oxid of manganese is used in con-
 siderable quantities.   Glass makers use  it in small  quanti-
 ties,  to deprive glass  of green and  yellow colors ; hence
 it has been called the soap of glass makers.  It probably acts
 by parting  with its oxigen, which uniting to the  coloring
 matter destroys  its color.   In  large  quantities it  renders
 glass of a violet  color.  The potters  use  it to give their
 wares a black  color;  and the chemists employ it in consi-
 derable quantities to yield oxigen air.

    Since it yields oxigen to the muriatic, and forming  the
 oxi-muriatic acid,  which is used for bleaching, no doubt it
  will come into much more general use. 
256
DISCOURSE  VIII.
FOURTEENTH  METAL,
                       COBALT.

   THIS  is a metal which has never yet been found pure
m nature.  It is met with generally in the state of an oxid,
or alloyed with some other metals or combined with acids.
In the state of an oxid, it forms the black cobalt ore, which
is found in Germany in masses,  or in the state of powder.
Alloyed with other metals,  it forms the dull white cobalt ore.
United to sulphur and arsenic, it forms the white cobalt ore.
And united to arsenic acid, it forms the brown cobalt ore.

   To obtain  cobalt  in a state of purity,  the ores contain-
ing it are roasted in the open fire, so that the sulphur and
arsenic flies off.  It  is then found in the state of  a black
oxid.   This is to be introduced in a  retort with charcoal
powder, and exposed to a most intense heat,  until the me-
tal is  fused.   It may be procured from the bottom of the
vessel, when removed from the fire, in a  tolerable state of
purity.  However it is commonly alloyed with iron.

   Cobalt when in a pure state, is of a steal grey color, with
a tinge of red, and a fine close grain. Its specific gravity
is about 7.750.  It requires a very intense heat to  melt it.
It may be  readily broken and reduced to a powder.   When
heated in contact with air, it is oxided before fusion.   It
unites  to metals,  rendering them brittle; but its alloys are
of no use. In its purest state,  it is not  only obedient to
to the magnet,  but according to Kahl and Wenzel,  it can
receive the magnetical power. 
DISCOURSE  VIII.
257
   Cobalt,  when oxided, unites to the acids, forming com-
 pounds,  distinguished  by the property of becoming green
 when  heated.   In  consequence  of  this,  they are used as
 sympathetic inks.  A very good ink of this kind may  be thus
 formed : Put into a vessel placed in  a very warm situation
 one part of cobalt,  and four of nitric acid, which must re-
 main several hours, till the solution is completed.  Then
 one part of common salt and sixteen parts of  water are to
 be added.   The solution is then to be filtered and kept for
 use.   If letters be written on clean paper with this solution,
they cannot be seen ;  but by exposing the  paper to a gentle
 heat, the letters will appear  of a fine green color, which
will disappear when the paper cools, and again appear when
heated.  This  change  of color is  supposed to arise from
variations in the quantity of  oxigen united  to the metal,
which depend on the heat.

  Cobalt is obtained from the ores of Saxony, in the state
of an oxid, forming the substance sold by the name naffer.
The zaffer of commerce is generally  mixt  with  said.  Zaf-
fer  mixed  with three parts  of sand and one of  potash,
forms  a blue glass, which when pounded in mills  and in-
cluded in  casks, forms smalt.   This smalt is  agitated in
 casks filled with water, and pierced with three openings, at
different heights.  The water from the upper orifice brings
out the lightest blue, which is called azure of the first fire;
the  heavier particles  fall more speedily; and the azure
brought out by the water of the three cocks, forms the dif-
ferent degrees of fineness, known under the names of azure
of the first,  second and  third fire.   Smalt is much used
in the preparation  of  various cloths.  The azures, when
 mixed with  starch,  form the  blues commonly used by
washing  women.   Glass  is generally colored blue  by this
article, and also porcelain.
                          Kk 
258
DISCOURSE Villi
FIFTEENTH  METAL.
                      NICKEL.

  ABOUT 1750 this metal was first discovered. Generally
it is found pure in the metallic state;  sometimes it is com-
bined with oxigen.   Its ores have  a coppery red  color,
covered more  or less with  a green powder.   The most
ore is that called Kupfernickle, in which the metal is united
to sulphur, forming a sulphuret of nickel: and also some
times with arsenic,  cobalt, alumine, &c.

  To obtain the metal pure, the ores should first be roast-
ed to expel the sulphur and arsenic ; it is then changed  into
a green oxid.   This may be  reduced  to the metallic state
by  mixing it with charcoal and common salt, and exposing
it to the  strongest heat of a  furnace.  The  metal  then
melts, and is  found in  the form of a button in the vessel.

   Nickel,  when pure, is of a pale flesh color.  When fresh
broken  it has  considerable lustre.   Its texture is compact,
and can be a little flattened by the  hammer,  as cast iron.
Its specific gravity is 7.380.   It requires a very intense
 heat for fusion.  It unites  to other metals, forming alloys
 of  no value.  Its attraction for iron is considerable, and but
a small quantity renders it magnetic.  It readily unites when
heated  in  open  vessels, to oxigen, forming a green oxid.
 The oxid unites to  the acids, forming compounds of no im-
 portance.   Its oxides are used to give a  hyacinth color to
 glass. 
  DISCOURSE Vni.              259

SIXTEENTH METAL.
                   MOLYBDENA.

  THIS metal is found but in small quantities.  It has been
found in Sweden, Germany, near the Alps, and in the island
of Lemis, about Scotland.  It is only found in combination
with sulphur, forming the ore called  sulphuret of molybdena,
which resembles so strikingly plumbago or black lead, that
they were long considered as varieties of the same species.

  To obtain the metal pure is very difficult.   The method
recommended is as follows :  Heat the ore for the sublima-
tion of the  sulphur, then powder the remaining part; mix
it with oil and expose it to an intense heat in a retort.  By
this means the metal may be obtained in the state of a pow-
der, brittle  under the finger, and possessing some lustre.
Its specific  gravity is about 7.000.   It is  one of the most
infusible metals.  It has a very strong attraction for oxigen,
and unites  to it in such quantities as to form an acid, called
the molybdic acid.  This, and no other preparation of the me-
tal is found of use.
SEVENTEENTH  METAL,
                   TUNGSTEN.

  THIS metal has only been found in small quantities,  in
France,  Spain, Britain,  Sweden and Germany.  Hitherto 
260
DISCOURSE  VIII.
it has only been found united to oxigen, forming an oxid,
and also an acid combined with lime.   The first ore is called
wolfram, and the other tungstate of lime.

   To obtain the metal in a state of purity,  its ores are to
be intensely heated with charcoal and potash,  but it is very
doubtful if the metal has been procured free from mixture.
The metal which chemists have been able to obtain from the
ores of tungsten, is of a steel grey color  It is very heavy.  Its
specific gravity being 17.06.   It is one of the hardest metals,
but is very brittle, and is as infusible as platina.  It com-
bines with sulphur,  copper,  iron, lead, &c. forming com-
pounds which have not been examined with  any care.  It
has a strong attraction for oxigen, and unites  with such
quantities as to be converted into an acid,  called the tung-
stic acid.   Neither this or its combinations have been found
of service.   It is, however,  supposed that it may become
useful in the arts of dyeing, as the color it  gives to other
substances cannot be destroyed by the oxi-muriatic acid, the
destroyer of all vegetable dyes.
EIGHTEENTH METAL.
                     URANIUM.

  THIS metal was discovered by Klaproth in 1789.   It
exists combined with  sulphur and a portion of iron,  lead
and silex, in the mineral termed pechblende.   Combined
with the carbonic acid, it forms the chalcolite, or green mi-
ea.   The ores are of a dark color, inclining to an iron grey. 
DISCOURSE VIII,              261
and possessing a little lustre.  They are found in the mines
of Saxony and France.

  To obtain the metal, the pechblende is first freed from sul-
phur by heat, and the oxid which remains is to be dissolved
in  nitric acid, and then precipitated by  an alkali.   The
yellow oxid falls down, which must be mixed with oil and
exposed to  a strong heat.

  Uranium appears as if it was composed of small metallic
globules, connected slightly together.   It is of  a deep  grey
color.   It  is very porous and soft,  has but little lustre, its
specific  gravity  is  6.440.   It is  more  difficult  to  be
melted  than  manganese.   It has been combined  but  with
few metals, and  has not been found of any value,




               NINETEENTH METAL.
                    TITANIUM.

  THIS  metal has  been but lately discovered.  It  exists
in a state of combination, in but  small quantities.   It has
been found in the ore named menachanite, combined with
oxigen and  iron ;   and also in  the red schorl of Hungary,
which is  of a brownish red color.

  It is difficult to obtain the metal pure.  For the purpose,
it is advised to melt one part of the oxid of Titanium, with
six of potash, which is  then to be dissolved in water.  A 
262
DISCOURSE VIII.
white precipitate will appear, which is to be mixed with rM
and charcoal, and exposed to a strong heat in a retort for seve-
ral hours.  The metal will then be had, of a reddish yellow
color and very brittle.  Its specific gravity is about 4.2.  In
a very intense heat it is volatilized.   It has been  applied to
no use hitherto, in a free or combined state.
TWENTIETH  METAL.
                    TELLURIUM.

  THIS metal has been discovered since 1796. It is found
in a state of combination with oxigen,  gold,  silver, copper
and sulphur.  It  exists but  in small quantities;  and has
been found  only  in  the mountains of Transylvania.  The
ores containing it are named as follows :

          1  Native Tellurium,
          2  Graphie ore,
          3  White ore,
          4  Foliated ore.

  When the metal is purified,its specific gravity is 6.110. It
is as fusible  as tin, and very volatile. When burnt, it smells
like raddishes  It has been united to several other metals,
but has not been found of use. 
    DISCOURSE VIII.              263

TWENTY-FIRST METAL.
                     CHROME.

  THIS is also a  new metal,  and is  found but  in  small
quantities,  in  the red lead ore  of Siberia,  in the emerald of
Peru, and it has also been found in a state of  combination
in the department of the Var in France, forming the ore
called the chromate of iron.

  This metal gives  a very bright  color to the substances
containing it.  It has a remarkably strong attraction for ox-
igen,  with which it unites, forming the chromic acid, which
is of a beautiful ruby red color.  This acid combines with
other substances,  forming compounds distinguished by the
brilliancy  of their  color.   By heating the acid with char-
coal,  it may be decomposed and the metal had pure,  in the
form of small masses of  a white color iuclining to yellow.
It has not been much examined; but from what is known,
it may be useful, it is probable to painters and enamellers.
TWENTY-SECOND METAL,
                  COLUMBIUM.

  THIS metal was only discovered in 1802 by Mr. Hatchett,
who received the mineral  containing it from  a  mine in
Massachusetts.  Nothing is known  concerning  this metal, 
■264
DISCOURSE  VIII.
 excepting that it unites to oxigen in sufficient quantities to
 form an acid called the columbic acid.

   Besides the twenty-two metals we have considered, there
 is another called tantalium which has been found in a small
 quantity in  Finland.   It has been procured from the mine-
 rals called tantalite and yttro tantalite.   Nothing is known
 of it of consequence; and it is likely tha£ it, as well as seve-
 ral of the last metals we have named, will hereafter be shewn
 to be compounds.  It will readily be perceived that the me-
 tals existing in greatest quantities, and most  useful, are a-
 mong those first described, and that iron, manganese, gold,
 silver, lead, mercury  and copper, are  found in the propor-
 tion to the other metallic bodies, as silex,  alumine and lime,
 are to the other earths.

   Upon the whole, however, it must  appear, from a survey
of what has been stated, that this globe of ours is composed
 of forty-six substances, which are to be, considered as ele-
 ments : To wit;

 4 Unconflnable bodies.

                  1  Heat or caloric.
                  2  Light.
                  3  Electricity.
                  4  Galvanism,

 1  Substance remarkable for causing acidity and  combustion.

                  1 Oxigen.
5 Carriedforward'. 
DISCOURSE VIII.
263
 5 Brought forward.
8 Substances remarkable for the compounds they form with oxigen.

                 1 Nitrogen,
                 2 Hidrogen,
                 3 Carbon,
                 4 Phosphorus,
                 5 Sulphur,
                 6 Muriatic acid or its base,
                 7 Fluoric acid or its base,
                 8 Boracic acid or its base>

2  Substances called alkalies.

                 1 Potash,
                 2 Soda.
9 Earths.
22 Metals.
1  Silex,
2  Alumine,
3  Lime,
4  Magnesia,
5  Barytes,
6  Strontites,
7  Zircone,
8  Glucine,
9  Yttria.
1 Mercury,
2 Platina,
46 Carried forward. 
266
DISCOURSE VIII.
46 Brought forward.
               5 Gold,
               4 Silver,
               5 Copper,
               6 Iron,
               7  Tin,
               8 Lead,
                9 Zinc,
               10 Bismuth,
               11 Antimony,
               12 Arsenic,
               13 Manganese,
               14 Cobalt,
               15 Nickel,
               16 Molybdena,
               17  Tungsten,
               18  Uranium,
               19  Titanium,
               20 Tellurium,
                21 Chrome,
               22 Columbium.
46 Elements.

  On taking a survey of what has been advanced concern-
ing these elementary bodies, we must be forcibly struck
with  the importance of oxigen, and the propriety of naming
the compounds, as is done in the new nomenclature. With-
out oxigen the number of compounds would be very much
diminished. The following, it may not be amiss to recapitu-
late.

   Oxigen unites  to most of the elements in different pro-
portions ;  and according to the quantity  of the oxigen  is
the nature of the compound formed. When it unites but  in 
DISCOURSE VIII.              26?
small quantities,  it forms compounds, distinguised by the
term oxid.  Hence we have, the

        Oxid of Nitrogen air,
         Do. of Carbon
         Do. of Sulphur
         Do. of Mercury
         Do. of Platina
         Do of Gold
         Do. of Silver
         Do. of Copper
         Do. of Iron
         Do. of Tin
         Do. of Lead
         Do. of Zinc
         Do. of Bismuth
         Do. of Antimony
         Do. of Arsenic
         Do. of Manganese
         Do. of Cobalt
         Do. of Nickel
         Do. of Molybdena
         Do. of Tungsten
         Do. of Uranium
         Do. of Titanium
         Do. of Chrome, and
         Do. of Columbium.


  But besides the above twenty-five oxids, we have several
others.   It is found that oxigen unites, in some cases, to the
same metal, in different  proportions; so as to change very
much the nature of the oxid.   In consequence of this, these
oxids are distinguished  from each other by their color.— 
268
DISCOURSE VIII.
Hence, we have the  black and the red  oxid of  iron; the
grey and the red oxid of tin, and so on.

   When several substances are saturated, with oxigen, their
properties are still more changed ; and  they are converted
into the compounds called acids, the properties of which we
considered when treating of oxigen. In consequence of this
we have 12 acids ; which are named according to the names
of their bases, or the substances uniting to oxigen, to wit:
1 Nitric	acid,
2 Carbonic	do.
3 Phosphoric	do.
4 Sulphuric	do.
5 Mariatic	do.
6 Fluoric	do.
7 Boracic	do.
8 Arsenic '	do*
9 Molybdic	do-
10 Tungstic	do-
11 Chromic	do.
12 Columbia	do,
  On further examination we find that the strength of these
acids is found to differ considerably. This arises from their
not being fully combined with oxigen:  yet they still possess
the properties of acids. Now to distinguish these acids from
the above, they  are named on the same principle, but the
termination of the name is made to vary from ic to ous. In
consequence  of this we have the three following acids, to
wit:
            1 Nitrous    acid,
            2 Phosphorus do.
            3 Sulphureous do. 
DISCOURSE VIII.
269
  Besides these acids, we have one more formed by the ad-
dition of oxigen to  the  muriatic apd, called oxi-muriatic
acid : making in the whole 16 acids, formed by the union of
oxigen with simple  substances.

  These various  acids are most remarkable  for uniting to
the akalies, earths, and metallic oxids, forming compounds,
called neutral salts;  of course,  the number of neutral salts
must appear very great.  However, some of the  acids do
not unite to some of the other bodies. To distinguish  these
salts from each other, names have been we find, very judi-
ciously selected from  the names of the acids, and those of
the bodies to which they unite.  The termination of the
name of the acid  is only a little varied.  When the acid is
perfect, and its name ends in ic, this is only changed into
ate; and when it ends in ous, this is changed into ite.   Now,
for example, the nitric acid, unites to potash; forming  a
neutral  salt,  which should be  called nitrate of potash: and
the same with the rest of the bodies ;  so that we have the
nitrate of  soda, of ammonia,  of lime, of mercury, &c. &c.
When the phosphoric, sulphuric, or  any other acids are
used, we have the phosphate, sulphate, carbonate, muriate, &c.
of potash,  of soda,  of ammonia, of lime, and so  on,  of the
the rest of the bodies  capable of uniting to the acids.

   When  the weaker acids are  used,  then the names are
changed.   The name of the acid as above ends in ous, and
this being changed to  ite, we have the names of nitrite,
and sulphite.  The compounds these form  are  therefore
called,

             Nitrite of Soda,
               Do. of Potash,
               Do. of Ammonia,
               Do. of Lime, 
270              DISCOURSE VIII.

And so on, with the phosphorus and sulphureous acids, with
the other bodies to which they unite.   But these  neutral
salts as well as most of those formed by the stronger acjds,
are found of no manner of use.

   But the above are  not the only kind of combinations.—
Many of the elements unite to each other forming  com-
pounds, without the aid of oxigen.  These compounds are
named, however, on the same principles.

   Carbon, sulphur and phosphorus,  particularly, are found
to unite with several other elements.  In this case,  when
the compounds are formed of carbon and other bodies, they
are called carburets.   Hence we have the carburet of iron, or
steel, and perhaps some other compounds.  When sulphur"
is used, the compounds  are called sulphurets:  Hence we
have the

             Sulphuret of potash, or liver of  sulphur,
             ---------of soda,
             ---------of lime,
             ---------of iron,
             ---------of copper,

and so on with the rest.   When the bodies  are united to
phosphorus, then  they are called phosphurets.  Hence we
have the phosphuret oj lime, of iron,  and so on  with the
 rest.

   The last combinations we have  to  notice,  are called
 alloys.  These are formed as is known already, by the unjgn
 of the metals with each other.                    f

   From the above short sketch, the advantages of the new
 nomenclature must appear very evident.   How could any 
                 DISCOURSE VIII.              271
one know the  constituents of  one hundredth part of
the many compounds which may be formed,  unless  the
name  give him some idea of the constituents ?  Indeed it
seems astonishing, that this method of naming these com-*
pou»ds  had not been earlier adopted.  It is founded on
principles which  are put in practice every day by the
youngest minds.  We constantly hear persons in speaking
of objects, give some idea of their composition.   Hence
we hear of a stone, of a brick, of a wooden, of a mud, and
of a straw house;  which are names just as remarkable, and
designed for precisely the  same purpose as the  sulphate,
muriate, nitrate and carbonate of  soda, or of any other sub-
stance.
 
DISCOURSE  IX.
   HAVING now given some idea of all the  elementary
 substances  which have been found in nature,  and having
 only glanced at some  of  the remarkable compounds met
 with in the mineral kingdom,  it will be  proper  here to
 dwell more particularly on the most important of them,
 by which  their qualities will be better  understood, and
 more correct  notions of the relative  importance of each
elementary substance will be formed.   And first, concern-
ing the waters which contain bodies in solution.  All these
may be classed under the head of


               MINERAL WATERS.
  WHILE considering water, it was stated that its power
of dissolving many substances was very remarkable; and that
when it had been  united to such in sufficient quantities as 
DISCOURSE IX.               273
 changed its sensible properties, it Was termed mineral  wa-
 ter.   The  properties of mineral waters depend on the par-
 ticular substance held in solution in the water ;  and the
 water is generally  designated by the name  of the mineral
 held in solution.

   But few waters more forcibly claim our attention  than
 those of the ocean, which every one knows contain great
 quantities  of saline substances, .particularly common salt.
 Indeed,  if  the sea were not impregnated with these saline
 bodies, the putrefaction of  the  immense  mass  of animal
 and vegetable matter which it contains, would shortly prove
 fatal to all living animals.

   The absolute quantity of sea water cannot be ascertained,
 as the mean depth of  the sea is  unknown.   According to
 the calculations of  Mr. de la Place,  it must be at least four
 leagues.   Even on the supposition that its  mean depth is
 not greater  than the fourth of a mile, its solid contents (al-
 lowing its surface to be three fourths of that of the super-
 ficies of the earth) would be 32,058,939 cubic  miles.

   Sea water has a very disagreeable  bitter taste, at least
 when taken from the surface, or near the shore;  but when
 brought up from great depths, it is only saline.   Hence  we
 learn,  that this bitterness is owing to the animal  and vege-
table bodies with which it is mixed  near the surface.   Its
specific gravity varies from  1.0269 to 1.0285.  It does not
freeze till cooled down to 28°

  By a number of experiments made by different chemists,
it has been ascertained that sea water holds in solution mu-
riate of soda, or common salt, sulphate of magnesia  and
sulphate  of lime besides the animal and vegetable bodies
   r                      Mm 
274
DISCOURSE IX.
with which it is occasionally contaminated.   The average
quantity of saline ingredients  is one  twenty-eighth.   It
was found  that water taken  up from  60 fathoms,  near
the Canaries,  contained about  one twenty-fourth.   One
hundred parts of this when analyzed was found to contain

               30.911 common salt,
               6.222 muriate of  magnesia,
               1.000 sulph^ of lime or plaster of Paris.

   Mr. Lavoisier found 10,000 parts of sea water, taken up
 on the west of the Dieppe,  to contain the following salts :

               1375 common salt,
                 256 muriate of  lime and magnesia,
                 156 muriate of magnesia,
                  87 lime,
                  S4 sulphate of soda and magnesia.

                19i8

  or almost one fifth of saline contents; but  this proportion
  is undoubtedly excessive.

    The common ocean is found to contain most salt about
  the equator, and some degrees towards the south of it.—
  The  quantity is less in nothern latitudes. The proportion al-
  so at different times is found to vary.   In the  Baltic, when
  an east wind prevails, only -rg-j- of the water is saline;  but
  this  proportion  is  doubled by  a  westerly  storm:  The
  Euxine  and  Caspian  seas, are  stated  to  contain   less
  salt  than the ocean; but  it is  probable that the Mediter-
  ranean is as salt as the Atlantic.

     The water of the Dead sea, differs exceedingly from sea
  water.   Its specific gravity is 1.2430, and it is saturated 
DISCOURSE  IX.
275
with salt,  containing no less than 44.4 per cent, of saline
matter : according  to  the analysis of Lavoisier, it is com-
posed of

            55  :  60 water,
            38  :  15 muriate of lime and magnesia,
             6:23 common salt,

            100 000

   Some remarkable cases have occurred,  in which the use
of sea water as a medicine, in doses of half a  pint a day,
proved of great service to  valetudinarians.   Bathing in this
water, has also  been found  beneficial.   The salts it con-
tains,  serve  to stimulate the  skin,  and thereby prove
strengthening to the whole system.
   BUT the appellation of mineral ivaters, is generally con-
fined to such  as  are  obtained  from springs, impregnated
with  substances, giving them some peculiar smell, taste,
color,  &c.  Many  of these springs attracted the attention
of mankind in the earliest ages ; and were resorted to by
those who  labored  under diseases.   But it has only been
since  the  middle of the 17th century, that attempts were
made to discover the ingredients of which these  waters
were composed, or to  discover the substances to which
they owe their properties.

   The substances found in mineral waters, are so numer-
ous, and some of them exist in such small quantities, that
it  will be  proper to dwell only on those which are most
remarkable.  These are the waters which contain airs,  tha
sulphuric acid,  and several neutral salts. 
276
DISCOURSE  IX.
  The different aerial fluids, ought to be first separated and
examined.   For this purpose a retort ought to be filled two
thirds with the water, and connected properly with a pneu-
matic tub filled with mercury.  The water should be made
to boil for a quarter of an hour, and the airs will pass over
into the jar.   When the apparatus is cool,  the quantity of
air expelled from the water will be seen, and allowances
should be made  for the air of  the retort.


   The only airs found in water are, atmospheric, oxigen,
nitrogen, carbonic acid, sulphurated  hidrogen,  and sul-
phureous acid airs.  The last two never exist in the water
together.  Having procured  the airs,  they should then be
 examined by chemical tests.  The quantity of oxigen may
 be determined on by burning phosphorus in it.   The quan-
tity of carbonic acid will be known,  by agitating it over
 lime water.   The presence of the sulphureous acid  may be
 known, by its being partially soluble in water, to which  it
 gives the properties of an acid.   Or if potash be added to
 the water, the  acid is more readily absorbed, and a sulphite
 of potash is  formed.  If sulphurated hidrogen  be present,
 it will burn in contact with  oxigen, and the products will
 be water and sulphuric acid, as may be noticed.   The re-
 maining air, it may safely be concluded, is nitrogen air.


    Atmospheric air is contained in  by  far the greater num-
  ber of mineral waters; its proportion  does not exceed one
  twenty-eighth  of the bulk of the water.


    Oxigen air was first detected in waters by Scheele.   Its
  quantity is usually inconsiderable ;  and it does not  exist  in
  them when sulphurated hidrogen air is present. 
DISCOURSE  IX.               277
  Nitrogen air was first discovered in Buxton water by Dr.
Pearson of England ;  it has since been detected in those of
Harrogate, and in those of Limington Priars.

  Carbonic acid was  first discovered in Pyrmont water by
Dr. Brownrigg.   It is  the most common ingredient in mi-
neral waters,  100 parts of it generally containing from 6
to 40 parts of this air.  It gives to them a  sparkling ap-
pearance like Champaigne wine.   They are taken as tonic
medicines.

   Sulphureous acid has been observed  in several of the hot
mineral waters in Italy near volcanoes.   Some of the waters
of this country contain it,  and  they are drank  for their
strengthening virtues.

   Sulphurated hidrogen air,  constitutes the most conspicu-
ous  ingredient in these waters which  are distinguished by
 the  name of hepatic or sulphureous.   They have a disagree-
 able smell, by which they are characterized.

   The presence of sulphuric acid may be readily detected
 in water, by  adding barytes  water.  The barytes unites to
 the  acid forming an insoluble compound, which should be
 separated.  One hundred grains of this compound contain
 23.5 of real sulphuric acid.

   The neutral salts commonly met with, are as follows :

    Sulphate of soda, or Glauber's salts.   This is not uncom-
 mon, especially in those  mineral waters which are distin-
 guished  by the term saline.   They possess a purgative pre*.
 perty when taken in large quantities.  The quantity of  this
  salt may be ascertained by evaporating the water. 
278
DISCOURSE IX.
   Sulphate  of lime,  or  plaster of Paris, is found in small
 quantities very generally in water.

   Sulphate of magnesia, or Epsom salt,  is almost constantly
 an ingredient  in such waters as have purgative powers. It
 was detected in Epsom water in  1610.

   Sulphate  of alumine,  or  alum, is occasionally met with.
 It may be detected by adding carbonate  of  lime, or magne-
 sia.  These  various sulphates may all be precipitated from the
 waters containing them, by  adding pure  ardent  spirit for
 which the water has a stronger affinity than it has  for these
 compounds.

   Nitre has been occasionally met with.  It may be detect-
 ed by partly evaporating the water and then on wetting and
 drying the paper it burns in a manner which  indicates  the
 presence of  nitre.  Dr. Woodhouse found it in considerable
 quantities in the pump waters of Philadelphia.

   Muriate of soda,  or common salt, is  so  very common in
 mineral waters,  that scarcely a spring  is found without it.

   Sulphate of iron, is also  frequently met  with in mineral
 waters, and also the carbonate of iron.   The  waters con-
 taining  iron may readily be  known by adding the prussic
 acid to them which renders them of a blue appearance, or
 by adding a decoction of galls, which renders them black.
 When the carbonic acid is united to iron,  on heating the
 water, the acid escapes and the iron falls to the bottom in
 the state of an Oxid.  The water containing iron (called cha-
 lybeate waters) are very  generally drank as a tonic medicine.
 They may be formed at any time, as must readily appear,
by art;  nothing  more being necessary than to add  the iron 
DISCOURSE IX.
279
in the state of an oxid,  to the water which has the acid to
be dissolved in it.
  For the particular means of detecting the exact quanti-
ties of substances in mineral waters, I must refer to a trea-
tise on this subject by Mr. Kirwan.   And Dr. Saunders has
published an exact account of the  virtues and constituents
of the most celebrated springs.   I  shall therefore conclude
this subject with the following statement, which will lessen
the trouble of analyzing water, as the compounds in the
first columns can never exist in  considerable quantities  in
water with those in the second.

           Salts                 incompatible with

„  ,  ,       r  „*T  „  ..   C nitrates of  lime and magnesia,
Sulphates  of tne alkalies, ]     .     , ,   &
Sulphate of lime,
  muriates of do. &c.

f alkalies,
■t carbonate of magnesia,
£ muriate of  barytes.
                         f alkalies,
                         j muriate of  barytes,
Alum (sulphate of alu.)  <j nitrate, mu. and car. of lime,
                         (^carbonate of magnesia.
Sulphate of magnesia,



Sulphate of iron,



Muriate of barytes,
 alkalies,
 muriate of barytes,
 nitrate and muriate of lime.

" alkalies,
 muriate of  barytes,
 earthy carbonates.

" sulphates,
 alkaline carbonates,
 earthy carbonates. 
280                DISCOURSE  IX.
          Salts                 incompatible with

                        0 sulphates,  except of lime,
Muriate of lime,        1 alkaline carbonates,
                        (_ carbonate of magnesia.

AT  •  ,    r              C alkaline carbonates,
Muriate of magnesia,    1 „  ,.     ,  ,     '
              °         £ alkaline sulphates-.

                        f alkaline carbonates,
Nitrate of lime,         } carbonates of magnesia and alu.
                        (_ sulphates,  except of lime.
   WE now come to the consideration of that part of che-
 mistry, termed Mineralogy ; as it has for its object the
 description of the  solids  of the globe, all of which are
 known by the term minerals.  These  substances,  without
 doubt, must have at all  times attracted the attention  of
 mankind;  because from them alone are drawn the metals,
 stones, and other similar bodies of indispensable use.   But
 it is only very lately, that the method  of  ascertaining the
 component parts of these  substances was  discovered,  or
 that it was possible to describe them, so as to be intelligible
 to others.

   Mineralogy, as far as it  is a chemical science,  includes
 under it three different  topics; namely,  an account of the
 properties and constituents of minerals,  an account of the
 various combinations these bodies form,  and the art of an-
 alyzing them.

   The description of minerals occupy a very conspicuous
part of  the works on mineralogy; and to favor this purpose
mineralogists have invented  a  language of their own, by
which they can readily give an idea of the external charac- 
DISCOURSE  IX.
281
ters of bodies.   But as it is not  consistent  with the nature
of this undertaking to enter so minutely into the considera-
tion of such particulars, we must refer to the works express-
ly written on the subject by Werner, Kirwan and  others.
Our attention will chiefly be confined to some remarkable
substances, which have a strong claim for consideration.

   In detecting the chemical properties of minerals the blow
pipe will be  of singular use, as it enables  us in a few mi-
nutes to determine many points which by the usual pro-
cesses would occupy a great  deal of time.   The blow pipe
is merely a tube, ending in a cavity as small as a  fine wire,
through which air is forced and made to play upon the flame
of a candle, by means of  which the flame is concentrated
and directed against small particles of the mineral  to be ex-
amined, either placed upon a bit of charcoal, or in a spoon
of silver or platina.   The air is either forced into the blow
pipe by the lungs of the experimenter,  or by means of bel-
lows attached to the  blow pipe.  By thus exposing a very
small portion of a mineral  to the concentrated flame, we see
the effect of heat upon it, and have an opportunity of trying
the action  of other bodies on it, at a very high temperature,
as of borax, soda, &c.  The properties which these experi-
ments bring into view, enable us, in many cases, to ascertain
the  nature,  and  even the component parts of a mineral,
particularly such as are metallic.

   Mineralogists  have very  generally  divided the mineral
kingdom into four classes:

             1 Stones,
             2  Saks,
             3 Combustibles,
             4  Ores.
                          Nn 
«82
DISCOURSE IX.
  The first class comprehends all the minerals which are
dfcmposed chiefly of earths :  The second all  the  combina-
tions of acids and alkalies which occur in the mineral king-
dom : The third those minerals which are capable of com-
bustion,  and which consist chiefly of sulphur, carbon and
oil:  The fourth, the  mineral bodies which are  composed
chiefly of the metals.
OF STONES.
  THE great  class of stones are  arranged by the miner-
alogists under  the heads of the elementary earths;  each
stone being considered as belonging to that kind of which
it  is chiefly composed.  Hence, all the stones  are to  be
numbered under the following heads.

            1  Silicious,
            2 Aluminous,
            3 Calcareous,  (or of  the  nature of lime)
            4 Magnesian,
            5 Barytic,
            6 Strontitian,
            7 Jargonian,
            8 Glucinian,
            9 Yttrian.

   However, a little consideration  will be sufficient to dis-
cover that there is no foundation for these divisions. Most
stones are composed of two, three, and sometimes four  in-
gredients :  and in many cases, the proportion  of two or
more is nearly equal.  It is  not consistent with the plan of 
DISCOURSE IX.
283
this work, to enter into the consideration of the particular
stones met with in nature.   The means of analysing them,
and determining to which  species they belong, may be
understood from what was said while considering each ele-
mentary earth.

  Before this analysis  is commenced, the mineral should
be reduced to a very fine powder.  This is by no means an
easy task when the stone is extremely hard. It ought  to be
raised to a bright red heat in a crucible, and then instantly
thrown  into  cold  water.  This  sudden transition makes
it crack and break to pieces.  If these pieces be  not suffici-
ently small, the operation must be repeated on each,  till they
are reduced to the proper size.  These fragments are then
to be  beaten  to small pieces in a polished steel mortar $
when the examination may be commenced with.
OF SALTS.
  THE number of salts met with in the mineral kingdom,
is not numerous.   They are named according to the names
of the acids and bases to which they are united. The me-
thod of analysing them may be understood from what was
said concerning the particular acids and substances for which
they have the strongest affinity. 
28*
DISCOURSE IX.
OF COMBUSTIBLES.
  THE combustible  substances belonging to the mineral
kingdom, excluding the metals, are all included  under the
following heads.

            1  Sulphur,
            2  Diamond,
            3  Bitumen,
            4  Pit Coal,
            5  Amber,
            6  Plumbago.
I. SULPHUR.
  SULPHUR  is frequently found in many parts of the
world, particulary about volcanoes, as  Hecla,  Etna, Vesu-
vius, the Lipari Islands, &c.  It is either in the  state of
powder or crystallized.  It maybe distinguished by its color,
smell, combustion, &c.  It may be separated from the sub-
stances with which it is blended, by means of heat,  as it
readily melts and may be made to sublime.
II. DIAMOND.
  OF  this enough was stated while considering it under
the head of carbon. 
DISCOURSE  IX.
285
III. BITUMEN.
  BY bitumen is understood,  by mineralogists in general,
an oil which is found in different parts of the earth, in va-
rious states of consistence.  These different states form dif-
ferent species, which have been arranged  as follows.
NAPTHA.
  THIS is found sometimes on  the surface  of the water
of  springs,  and  sometimes  issuing  from  certain spots.
It is fluid and trsnsparent;  of a white  or yellow color;
strong, but not disagreeable smell; feels greasy ; burns very
readily with a white flame and leaves scarcely  any thing be-
hind.  It is  not  soluble in alcohol.  When exposed to the
air,  it becomes yellow, and then brown.  Its  consistence
increases, and finally it passes into

                    PETROLEUM.

  THIS substance is found in Persia, and likewise in many
countries in Europe, particularly, Italy, France, Switzerland,
Germany, Sweden, England,  and Scotland.   It is not so
fluid or  transparent as  water.  Its color is yellow, either
pale or with a shade  of red or green ; reddish brown and
reddish black.  Its smell is less pleasant than that of Naptha.
When burned, it yields a soot, and leaves  a  little coal be-
hind.  By exposure to the air, it becomes like tar, and is
then called 
286
DISCOURSE IX.
                  MINERAL TAR.

  THIS substance is found in many parts of Asia, America,,
and Europe. Its consistence is thick; of a black, brownish-
black, or reddish color ; smell sometimes strong, but often
faint.  When burned, it emits a disagreeable smell.  By ex-
posure to air it passess into

        MINERAL PITCH AND  MALTHA.

  THIS has a strong resemblance to common pitch.  In
warm weather it is soft, and is then called adhesive  mineral
pitch.  When the weather is cold, it is brittle ; and when
broken, has a glassy lustre. In this state it is called maltha.
Color, black, dark brown or reddish. In a high heat it burns
and  leaves a quantity of grey ashes.   When it  is further
hardened, it passes into

                      ASPHALT.

   ASPHALT is found abundantly  in many parts of Eu-
rope, Asia, and America,  especially in the island of Trini-
dad.  Its color is black, or brownish black. It feels smooth
but  not  greasy.  Does not stain the fingers; and has no
smell unless rubbed or heated.  When heated, it melts and
burns almost entirely away.  This article is manufactured
in France, and is used for  greasing the wheels of carriages.
               ELASTIC BITUMEN.


  THIS  substance was  found about the year 1786, in a
mine  in  England.   Its color  is  either yellow, reddish, or 
                   DISCOURSE IX.               287
blackish brown.  In  appearance, it has a strong resemblance
to elastic gum, or Indian rubber: hence its name.   Its con-
sistence varies.   Sometimes it is so soft as to adhere to the
fingers;  sometimes it is as hard as asphalt.  When soft, it
is elastic ; when hard it is brittle.  It is insoluble in alcohol,
oil of turpentine :   but it is soluble in oil of olives.  When
distilled, an oil comes over,  and the residuum is carbon.
There is a variety  of it,  strikingly like common cork
when  fresh  cut;  but in a  few  days after being  expo-
sed to the air, it become* of a pale reddish brown.   This
substance seems  to be  the elastic bitumen, altered  in  its
texture by water.
IV. PIT COAL.
  THE substances belonging to  this head,  are composed
chiefly of bitumen, and carbon,  existing in the  state of an
oxid or charcoal.
JET.
  THIS substance is found in France, Spain, Germany,
England, and other countries.  It is found in detached kid-
ney form masses of various siz*es, from an inch to 7 or 8
feet in length,

  Its color is full black ; it has considerable lustre  when
broken; it has no odour unless heated.  It molts in a strong 
288
DISCOURSE IX.
heat,  burns of a greenish flame,  and leaves an earthy resi-
duum.  By friction it becomes electric ; and when distilled
it yields a peculiar acid.

  This mineral is formed into  buttons, beads,  and other
trinkets,  in France, where its manufacture  is  chiefly con-
fined.



                   CANAL COAL.


   THIS mineral is found in Lancashire, and in different
 parts of  Scotland,  where it is known by the  name of  par-
 rot coal.   Its color is  black;  its structure sometimes flaty;
 it is brittle, and does not stain the fingers.   It kindles easily,
 and burns with a bright white flame like a candle, which
 lasts  but a short time.  It is susceptible of a good polish,
 and is frequently wrought into trinkets.  A specimen of  it
 when analyzed was found to contain

               75 : 20 charcoal,
               21 : 68 maltha,
                 3 : 10. alumine and silex.
99 : 93.
COMMON COAL.
  THIS very valuable combustible is found in great abun-
dance in many parts. Its color is black, more or less, perfect, 
DISCOURSE  1%.               289
Fts structure, more or less, slaty.  It usually stains the fingers.
It takes fire more slowly, and burns longer than the last spe-
cies.  It cakes more or less during  combustion.  Its com-
bustion  in the  common  way is, however,  very imperfect.
A considerable  quantity of the carbon is carried off in the
forrn of smoke, or falls  to the bottom of the grates, in
which  it is burnt.  This  inconvenience may be readily a-
voided if  the coal be  previously reduced to a fine powder,
and then  wetted up with one third or one half of common
clay, and then made into small cakes and dried.  These
cakes burn with great readiness, and throw out much heat,
as the combustible matter being in a state of division, more
readily unites to the oxigen of  the  air, forming fixed air,
which escapes  without  smoke.  It has been ascertained
by the experience of many that it is  of great advantage
to  have  coal mixed  as above  with clay ;   and that these
advantages  are far greater than  the  trouble  of making
the mixture.

   Of this species of coal, there are several varieties found
in mines of  various countries.  They are distinguished by
 the names of caking coal, rock coal, &c.  When analyzed,
they are  usually found to contain from 50 to  80 parts in
the hundred of charcoal.  The bitumen maltha,  is found
in them generally  in small quantities ; also, sulphur,  and
 from one to six parts of earths.

   In some species of this coal, the bitumen maltha is found
 in considerable quantities.  In consequence of this it has
 been proposed to separate it by means of heat,  and apply
 it in cases where pitch made of common tar cannot be pro-
 cured.    At one time the expectations in  favor of its pro-
 ving of  value were considerable;  but these have lessened
 very much, in consequence of its application, particularly 
290               DISCOURSE IX.
to the bottom of  ship?,  proving of no service after a iew
months.

   The  quantity of sulphur found  is also considerable in
 some instances.  This coal emits a sulphureous smell while
 burning, which  is so disagreeable,  that the  value of the
 ooal is much lessened.  In general the purity or excellence
 of the coal may  be judged of by its containing least  sul-
 phur, and greatest quantities of charcoal,  which is carbon
 oxided,  in which state it burns readily.

   This species of coal, when reduced to a fine powder,  is
 a most excellent manure.   A number  have tried it some
 years since ;  but have not derived all the benefit it is capa-
 ble of affording, in consequence of not reducing it to a pow-
 der sufficiently  fine.  From  experiments which I have
 made, in which I took  such  care to destroy the cohesion of
 the coal, so as to have it in the state of the finest flour, it ap-
 pears that  the coal is the very best  manure which is used.
 Indeed if its cohesion be  sufficiently destroyed,  it cannot be
 otherwise :  for the carbon it contains, is the chief constitu-
 ent of plants, and they must unite to it while growing.

    Immense mines of this coal are met with in this country.
 Near Richmond, in  Virginia, it is found in great quantities,
 and of excellent quality.   And on the banks of the Poto-
 mac,  some hundred miles  above the city of Washington,
 inexhaustible mines of it, of equal value, are met with.   In
 faking a view of the extent and importance of these mines,
 ©n the Potomac, it is impossible  ^o. feel otherwise than
 forcibly struck with  the  providence of  the Creator !  We
 perceive the certainty with which the seat of the federal
 government has  been the favored spot of a benevolent God,
 as well as a beloved Washington ! 
                  DISCOURSE IX.               291

                     V.  AMBER.



  THIS substance, called electrum by the ancients, is found
in different  countries ; but  most abundantly  in Prussia;
either on the sea shore, or  under ground at the depth of
120  feet.   It is met with in lumps of different sizes.

  It has a yellow color, considerable  transparency, and be-
comes electric by friction.   If a piece of it be affixed to the
point of a knife and then kindled, it burns to the end with-
out melting.

  By  distillation it yields an acid, called  the  succinic acid.
This  acid exists in a solid state; is  soluble  in twenty-four
parts of cold and two of boiling water.  It is slightly  solu-
ble in alcohol.
VI.  PLUMBAGO.
  OF this coal we also treated while  considering carbon.
It differs from commom coal in containing more carbon and
iron.   It is called also black lead.
  THE  composition  of the various substances abounding
with coal may be  readily ascertained.   When the coal is
burnt, the ashes should be examined, by which a knowledge
of the earths contained in the coal may be acquired.   To
ascertain the quantity of carbon, a  given quantity of the 
292
DISCOURSE IX.
coal  should be heated in a retort,  connected with a pneu-
matic tub ; then the nitric acid,  or common nitre, should
be added to  it,  while an air comes over.   The oxigen of
the nitric acid unites to the carbon, forming carbonic acid,
which escapes in the form of air : and in proportion to the
quantity  of this  air is the quantity of carbon contained in
the mineral experimented  upon.    By these means, the
quantity  of carbon in any soil may be ascertained.

   By deducting  the weight of the earths, and that of the
carbon which united to the oxigen, forming carbonic acid,
an idea  of the  quantity of bitumen in  the coal may be
formed.
METALLIC ORES.
   THIS class comprehends all the mineral bodies, com-
posed either entirely of metals, or of  which metals  consti-
tute the most considerable and important part.  It is from
the minerals belonging to this class that all metals are ex-
tracted ;  for  this  reason they have  obtained  the name
of ores.

   The various ores are arranged  under 22 heads,  which
bear the  names  of the metals most remarkable in them.
The method of  analyzing  them may  be understood from
what was said concerning each metal.  For more particular
accounts than I have  given,  I must  refer to treatises ex-
pressly written on the subject.   Mr. Kirwan's is  gene-
rally read. 
DISCOURSE  X.
   THE  attention of the chemist is early attracted by the
great variety of compounds obtained from matter organized,
or in other words, the products formed by vegetable and
animal parts.  It is well known that these products vary in
their qualities almost in an  infinite degree ; scarcely any
two of them are found possessed of precisely the same pro-
perties.  This  must excite very  much our astonishment,
when  sensible that  all these  innumerable compounds are
wonderfully formed, by the union of not 50 different sub-
stances.  Our surprise must be still more excited, when it is
considered, that but a small part of these few elements en-
ter into the composition of animal and vegetable parts.  By
means of heat, all the variety of compounds may be redu-
ced to  the elementary state ; and it will be found that all ve-
getable parts are chiefly composed of carbon, oxigen,  and
hidrogen, and all animal parts of the same elements with 
294
DISCOURSE  X.
nitrogen,  phosphorus, and  lime.   Sulphur, the  alkalies,
iron,  gold, manganese, and silex, are  also discovered in
their composition,  but only  in small  quantities.  Perhaps,
latent heat, light,  and electricity,  have  much  greater in-
fluence than the last named elements.

  As no advantages rusult from that decomposition of ve-
getable and animal parts by fire, by which they are restored
to the  elementry state, we  will not enter particularly into
the consideration of the  means which have been  pursued
for the purpose.  However, there is another kind of decom-
position which these substances undergo, by which they are
converted to certain states, in which they possess particular
general properties.   When changed into these  states, they
are called proximate principles.   We will first consider the
composition of vegetable bodies.

   Although every plant  has qualities different  from other
plants ; and although different parts of the same plant have
different properties, yet all these compounds may easily be
reduced to a few states, in which they  are alike.   These are
called the proximate principles.   The proximate principles
of vegetables, or the states to which they may all be reduced,
do not exceed sixteen.  When reduced to these states they
are called as follows:

            1 Wood, or ligneous fibre,
            2 Acids,
            3 Tannin,
            4 Oils,
            5 Gluten,
            6 Fecula,
            7 Indigo,
            8 Sugar,
            9 Gum., 
DISCOURSE X.
295
          10  Resin,
          11  Extract,
          12  Elastic gum,
          13  Camphor,
          14  Wax,
          15  Bitter principle,
          16  Narcotic principle.

  These will be treated of in the order in which they are
named.
                      WOOD ;

                          OR
                 LIGNEOUS FIBRE.


  THIS forms chiefly the solid parts of vegetables, parti-
cularly of trees.   It consists of a number of  small fibres
longitudinally  arranged, and it supports and acts  as a re-
servoir for the fluids of the vegetable.   It may be exhibited
pure, if shavings of wood be  repeatedly boiled in water
and ardent spirit.   It will be  found insoluble, of  a white
color, and combustible.   It contains a little oxigen and hi-
drogen, with  which however it parts,  if heated in a close
vessel, and  there remains behind the  carbon,  of which it
was  formed, which retains the shape of the original mass.
Carbon is therefore its chief  constituent.   This woody
matter  exists  in  greatest  quantities in black ash, common
oak, guaiacum,  hickory, &c.   It  is very remarkable for
resisting putrefaction.  For  years, and almost centuries,  it
sometimes remains  without decaying.   The  time in which
w©od resists decomposition,  depends very much on its state 
296                 DISCOURSE X.
of purity.  The substances or juices of the tree with which
the wood is blended, tend very much to hasten its decay.
Hence, by exposing logs to heat, which evaporates the fluid
parts, their duration is protracted.  On this is  founded  the
practice of burning or charring posts introduced in the earth.
The advantages derived  from the evaporation of such flu-
ids, are clearly shewn by the longer time which logs remain
that have been sawed through, than those  not  opened.
Judge Peters of Philadelphia has published a most valuable
paper on this subject, in which he clearly shews the impro-
priety of painting green wood ; as the paints prevent the ex-
trication of the volatile parts within.  In a conversation I
had with the venerable  and hospitable Mr. Henderson of
Dumfries, Virginia, he  stated that the advantages derived
from having timber from trees sawed  through, or split open
through the middle, were very surprising. Fifty years ago this
wealthy gentleman had a house built in Colchester, of logs
divided longitudinally through the heart; and they retain
their original firmness at this day;  while those built in the
neighborhood without this division  of the timber, have long
since decayed.   It has also been found that logs last longer
after they remain  some time under water.  No doubt but
the water acts  as  a preservative by dissolving and carrying
off parts of the wood disposed  to decay.   The common
notion is that it carries  off  an acid.   It appears to me, as
the  solvent power of water is much increased by heat,
that  in  parts  where  it is a great  object to  have  timbers
to remain  long,  considerable good might  be derived by
boiling the logs, in a  large  contrivance  for the  purpose,
before using them. 
DISCOURSE X.
297
II. ACIDS.
   IN various states of combination  in  a great variety  of
 plants, we find juices remarkable  for  exciting  the  sen-
 sation of sourness.  This arises from the acids they contain.
 These  acids when particularly examined, are found to  be
 but seven in number, and diffused in different states of com-
 bination.   They are called native vegetable acids, and are
 named, the

               Citric,
               Malic,
               Oxalic,
               Gallic,
               Benzoic,
              Tartareous,  and
               Acetic acids.

   These acids have for their bases, combinations of hidro-
gen and carbon, and owe their acidity to the oxigen they con-
tain. In consequence of this, they may frequently be formed,
and  converted  the  one into the  other by art.    They all
unite to the alkalies, earths, and oxids, forming compounds
which are of  very little known value,  and consequently our
remarks concerning the whole will be but few.   The co
pounds are to be named as heretofore,
PP 
!3«               DISCOURSE  X.

                   CITRIC ACID;
                           OR
                ACID OF LEMONS.
  THIS exists in the juice of lemons in the largestquantities.
It is also found in oranges, unripe grapes, cranberries, bil-
berries and a variety of other sour fruits.  It may be had m a
state of purity by the following process.  To 100 parts of
boiling lemon juice, add about four parts of chalk : a preci-
pitate will appear consisting of the citric acid and lime (citrate
of lime) which must be separated and washed in water.—
Then add  to it, about  20 parts of sulphuric acid, diluted
with six times its weight of water, and boil the whole for
an hour, agitating it during the whole time. The sulphuric
acid unites to the lime, and the citric  acid remains in the
 water ; and if evaporated, it crystallizes.   To be had pure,
 it must be dissolved and crystallized several times.  This
 acid may long be preserved pure.   It has a most delightful
 taste, when diluted with  water ; and hence it is used for
 punch. In a high heat it is decomposed and converted into
 carbonic acid ;  and carbonated hidrogen  air, and a little
 charcoal remains.
  MALIC  ACID;
         OR
ACID  OF APPLES.
  THIS  acid is found in the juice of unripe apples;  and
in those of barberries,  elderberries, gooseberries, plumbs, 
DISCOURSE  X.               599
and the common house leek.   To prepare it, take the sour
juice of apples; saturate it with potash, and add the sugar
of lead, while a precipitate appears.   This is malate of lead;
to which sulphuric acid should be added till the liquid is
sour,  without any mixture of sweetness.  The malic acid
will remain in  the water, while the sulphuric is united to
the lead.  This acid can only be had in  a fluid state.  Its
taste is an unpleasant sour; and it undergoes a decomposi-
tion when exposed to the air.
OXALIC ACID.
   THIS acid is prepared only by art.  In order to procure
it, boil in a retort one part of white sugar, with four of ni-
tric acid.  When the fluid acquires a brown color, add two
parts more of the acid, and  continue the heat while the
fumes arise;  when the mixture cools the acid will crystal-
lize.  This acid contains more oxigen than  any other vege-
table acid.   It is  remarkable  for its  strong  attraction for
lime;  which being superior to any other  acid, it is used to
detect  the presence of lime  in all its combinations:  In  a
high heat it  is decomposed into carbonic acid,  and carbon-
ated hidrogen air.
GALLIC ACID.
  THIS acid exists in nut galls; in the husks  of nuts;
in oak bark;  the persimmon tree; and in all those vegeta- 
300
DISCOURSE  X.
bles called astringents.  The acid may be obtained pure by
exposing powdered nut galls in a retort to a moderate heat.
The acid  by this means sublimes, and  a part condenses  in
small white crystals in the necks of the retort.

   This acid is sour and astringent, when dissolved in wa-
ter : it strongly reddens blue vegetable colors. It sublimes
in a gentle heat, but is decomposed in a higher temperature.
It has  a strong tendency to unite with metallic oxides. With
the red oxid of iron, it is remarkable for producing a deep
black  precipitate, which is the basis  of black ink  and  dyes.
Hence it is a  good  test,  by which the  presence of iron
 ma.y always be detected in any fluid.

   A good ink may be  prepared  by  digesting a strong infu-
 sion of galls over  the  red  oxid  of  iron;  to which,  when
 black, a little gum arabic should be added.  When the nut
 galls  cannot be procured, the unripe juice of persimmons,
 or a  decoction of oak bark will answer.  The best  ink, it is
 Stated, is thus made  : take two quarts of water;  one ounce
 of rasped logwood, and two ounces  of gum arabic, and boil
 them till half the  water is evaporated.  Then let the  liquid
 be strained, and add to it three ounces of nut galls,  1 dram
 cloves, and one ounce of copperas (sulphate of iron): This
 should be stirred repeatedly, and preserved for use in stopt
 vessel,. Writing with this and common inks maybe effaced,
 by wetting the paper with the  oxi-muriatic acid  in water.
 It may however be restored, by putting the paper in a weak
 solution of the sulphuret of ammonia ;  and this will also re-
 store the color of old writing.  If  indigo and  the oxid  of
 manganese be added to inks, they  cannot be destroyed by
 the above acid.  A  little  loaf sugar is sometimes  added to
 give inks a shining appearance. 
DISCOURSE  X.
301
BENZOIC ACID.
  THIS acid exists in considerable quantities in the resin
called  benzoin ; in the balsams, in  liquid storax,  in glue,
silk wool, sponge, mushrooms, &c.  It may be  obtained
pure by exposing  benzoin to a gentle heat,  in a bason co-
vered with blotting paper.   The acid sublimes and adheres
to the paper.   This acid when pure is void of odour.  Its
taste is irritating, and it is not very soluble in cold water.
It unites to other bodies forming benzoates, which have not
been examined.
TARTAREOUS  ACID.
  THIS acid exists in the juices of grapes and many vege-
tables,  most commonly in combination  with potash and
lime.   It is obtained chiefly from grapes,  in which it exists
in combination with potash.  The common cream of  tartar
of the shops is obtained from grapes, and is composed of
this acid and potash.  The acid may be  had in  a state of
purity,  by taking two pounds of cream of tartar—dissolve
them in water, and add  chalk as long as a precipitate ap-
pears.  This precipitate is the tartrite  of lime, which is to
be put in a vessel with 9 ounces of sulphuric acid and 5 of
water.  After remaining 12 hours, with occasional stirring,
the tartareous acid is set at liberty, and dissolved in the wa-
ter.   The solution may  be evaporated and crystals of the
acid will appear.   This acid is exceedingly sour, is not al-. 
JJ02
DISCOURSE X.
tered by the  air,  and is  very soluble  in water.  It  has a
strong tendency to  unite to potash;  and  in  combination
with this alkali, it forms


               CREAM OF TARTAR;

                          or.

      ACIDULOUS TARTRITE OF POTASH.


  THIS compound is obtained in great quantities from va-
rious wines while fermenting.  It is deposited  on the inner
sides of casks in various quantities.  The Hungarian wines
afford smallest quantities  ; the wines of France yield more,
but the Rhenish wines afford most.  When taken from the
sides of casks after they are opened,  it is  called crude tar-
tar,  and is red  when obtained from red wines.  To purify
the tartar,  it is dissolved  in hot water,  and  suffered to crys-
tallize after cooling.  These crystals are again dissolved and
crystallized,  and are then sold under the name of cream of
tartar. This compound has  an acid taste in consequence of
being fully saturated with potash.  It  is not very soluble in
cold water.   But if a little  potash be added to saturate the
excess of acid, it then becomes a pure tartrite of potash, and
is much more  soluble in water.   TI12 compound, called
cream of tartar, should therefore be termed acidulous tar-
trite of potash.  In  some places this salt is used to season
food, to make punch,  and  more generally, as a medicine,
in doses of near an ounce. 
DISCOURSE  X.               303

ACETIC ACID,
        OR
   VINEGAR.
  THIS acid exists in small quantities in cream of tartar,
and in some other vegetable products.  But it was obtained
chiefly by the  acetous fermentation of vegetable  substances;
and is the acid which gives the sourness to vinegar. Vinegar
is formed very generally, by the fermentation of wine, cyder,
beer, or any fluid which has undergone  that fermentation
called vinous, by which a substance termed spirit, possessed
of an intoxicating quality is formed.

   But it should be observed that this spirit, when in a pure
state, or only diluted with water, will not undergo this ace-
tous fermentation.  Besides the presence of the  spirit, there
must be  some extractive or mucilaginous matter present*
Hence Mr. Chaptal long exposed pure old wine  to the open
air at a proper temperature, but it  was not  rendered sour.
On adding, however, vine leaves to the same wine,  and on
adding other  extractive matter to mixtures of spirit  and
water,  they readily fermented.   When such kind of matter
is present in sufficient quantities  to cause the process to
commence, then the strength of the products is in proportion
generally to the quantity of  spirit in the fluid.

   For this acetous fermentation to take place in such fluids,
 they should be placed in a warm situation, and the air should
 be allowed to  have  free access.   When this  is  the case,
 the fermentation soon commences ; the fluid appears mud-
 dy ;  its  surface becomes covered  with  a muddy pellicle ;
 the  fluid loses its taste and odour; it becomes sour; a
 quantity of mucus matter  is separated, and forms a kind 
304
DISCOURSE X.
of skin, which sinking down  is vulgarly oiled mother of
vinegar;  oxigen is absorbed from the surrounding air;  and
the sourness  increases till the process is ended; so  that
good vinegar is formed.   Vinegar when fully fermented, is
clear and nearly colorless; it ha-, a pleasant odour and taste,
and possesses  all the properties of acids.   When distilled
the acetic acid  to which it owes its properties, rises in the
vessel and is condensed, constituting pure acetic acid.   The
quantity of this acid is in proportion to the  strength  of
the vinegar.

   Acetic  acid is very volatile ; its fumes are too strong to
be agreeable; it  acts as  a  caustic  on animal matter; and
it unites to the alkalies,  earths and metallic oxids, forming
compounds called acetates, most of which have not been ex-
amined.   The most useful are the  two named elsewhere;
to wit, verdigris, or acetate of copper, and sugar of lead,  or
acetate of lead.

   The acetic acid, under some circumstances, parts with a
 portion of its oxigen, and it then constitutes the acid called

                   ACETOUS ACID.

   This is a colorless fluid, less active than the acetic acid,
 and contains  less oxigen.  Its smell is suffocating.  It
 unites to the common bases of  the acids,  and forms com-
 pounds which have not  been  much examined.  They are
 called acetites.
  BESIDES the above seven acids, there are several of a
similar kind, which are formed during the decomposition
of some vegetable substances.   Such, are the acids called 
DISCOURSE X.
305
pyro-mucous, pyro-ligneous, pyro-tartareous, the succinic, sube-
ric  and camphoric acids.  The first three are found to be
the acetic acid, disguised with fetid oil.
SUCCINIC ACID.
  THIS is obtained by the distillation of a bituminous sub-
stance, of a yellow color, called amber, which is found in
some places.  It exists in a  solid form and has a strong
acid taste.   It is not much known.
SUBERIC AND CAMPHORIC ACIDS.
  THE first is obtained by distilling nitric  acid over cork,
and the second by distilling the nitric acid over camphor.
The acids have not  been much examined.   It is probable
that these and many more, which might be formed by vari-
ous combinations, are not worthy of attention.
III. TANNIN.
  THIS is one of the constituents of vegetables, and was^
until lately,  confounded with the gallic acid.  It is a sub-
                         Qq 
:506               DISCOURSE X.
stance of great importance,  as it is only by it, that we-are
enabled to tan leather : hence its  name.   However, it  is
not  u;et  with in great  quantities in the vegetable king-
dom.  Its most essential qualities  are as follows: It ha3 an
astringent taste; is soluble  in water and  ardent spirit:  it
unites  to animal  jelly,  forming  an  insoluble compound:
with the salts of iron it forms a deep blue or black color.
It may be obtained in a tolerable state of  purity by adding
powdered nutgalls to hot water;  stirring the mixture for
some time,  and then pouring off and evaporating the de-
coction,  by a slow fire.  The tannin  will then  remain  in
the form of  a  dark mass.   If small  quantities  of animal
jelly, dissolved in much water, be added to the decoction
containing the tannin, the  two unite together, forming an
insoluble compound, by which the quantity of tannin pre-
sent may be  judged  of.   However,  if  too much jelly be
added,  this compound will be dissolved by the jelly.

   The largest  quantities of tannin are  contained in the
 Bombay catechu, and in nutgalls; but  as these articles can-
 not be  had  in sufficient quantities for the purpose of tan-
 ning leather, it is usually  procured  from other vegetable
 substances;  and particularly the  inner bark  of trees.  Of
 the several  trees containing it,  the  largest quantities are
 found in the barks of the Leicester, or Huntington willow,
 of the common oak, smooth oak,  and of  the Spanish ches-
 nut.  The barks of these trees are taken off in the spring,
 and then by mechanical contrivances are reduced to powder,
 in which state, they are  put in  vessels  containing  water
 with the hides of animals which are to be tanned.

   The larfe and thick hides receive  their color from the
          O
 infusion of bark ;  after this part of the process is ended, it is
 common among tanners to  put the hides  into water slightly
 impregnated with sulphuric acid, or with the acid evolved 
DISCOURSE  X.               307
during- the fermentation of barley and rye.  This renders
them harder and fits  them for  forming sole leather.  The
tanners also put their small skins, designed for fine leather,
in water, to which pigeon's dung which has not fermented,
is added. This infusion is called the grainer, and it is stated
that it renders the  leather  thinner, softer, and more proper
of course for making upper leather.  What real advantage
is derived from these mixtures is not exactly ascertained.
But it is certain that the processes of common tanners may
be very much  shortened.   And instead of requiring from
six months to two  years to make leather, it can no  doubt be
done  in a few weeks or days.

   It was formerly supposed that the  tanning of leather de-
pended  on the power of barks, to constringe together the
fibres of the hides  of animals.   But this supposition is not
correct.   The new qualities of skins acquired by tanning,
depend  on the chemical union of the tannin  of the  barks
with the  animal gelatine,  or  jelly of the hide  ; (of which
jelly great quantities exist  in hides, as will appear by boiling
them.)  In consequence of having ascertained  this truth,
leather can now be tanned in a lesser  number of days,  than
formerly required weeks;  and perhaps in a lesser number
of hours, without any increase of expense or labor.

  The  process for tanning leather, which Mr. Seguin of
Paris has practised  with  great  success, is the following.
Instead of shaving the hair from skins,  they are to be freed
of it by means of  lime;  as the lime not only removes the
hair,  but destroys  the outer covering of the skin, which
only  serves to impede the  union  between   the  tannin
and jelly.  To effect  this,  some slaked lime  should be
thrown in a pit of  water,  and well  stirred:  the  hides
should be kept in this lime water, which is repeatedly  to
be agitated  for seven or  eight days, when the hair  fnay 
308
DISCOURSE  X.
be removed with facility.   This being done, the hides  are,
as tanners term it, to be raised, ox swelled.  For this,they are
to be introduced in water, one  thousandth part ox which
is sulphuric  acid, and kept in it about  two days.  They
now acquire  a yellow color, even in their interior,  as may
be seen by cutting them.   This  being done, they are ready
for tanning.  A method stated  to be superior to this  for
bringing them  to this state, is one by which the hair may
be removed and the hide raised in two days.  This is done
by plunging the hides in old tar water, to which  is added
five parts  of sulphuric  to 1,000 of water,  and  allow-
ing them to remain in it for two days, at which  time the
hair may  readily be removed, and the hide will be found
raised.  But it  is actually stated,  that although the practice
of raising hides be  so common,  it is  in reality of no service
to them.

   The hides being deprived of their hair  and swelled or
not, as it may  please  the operator,  he should  thus  pro-
ceed,  instead   of  laying  the hides in a  pit  with water
and powdered  bark, he  should prepare a strong  solution
of tannin in  water.   This can be done  by having a num-
ber of  tubs  filled with  the powdered  bark: on  these a
quantity of water,  (the better if warmed) is  to be poured,
and as it is drawn off from the first, it is to be added to the
second, then to the third, &c.   Water should constantly
be poured on the first,  until it comes off clear,  so that no-
thing may be lost.  The solution is to be kept in casks for
use, and it is particularly in the  use of this solution that the
present superiority of tanning leather consists. So soon as the
hides are taken  from the water and sulphuric acid,  they are
to be  placed in a weak solution of tannin for  two or three
hours; they are then to be taken  out, and introduced in the
strongest solution of tan, in such a manner, that their sides
may be kept apart about an inch; this can be done by sus- 
DISCOURSE  X.
309
 pending them  by one edge.  The time in which the hides
 should remain in this solution, depends on their thickness :
 from five to twenty days,  however, completes the process,
 which may be determined on, by cutting the hide, as when
 properly tanned  no white streak will appear in its middle.
 When taken out of this solution they should be dried with
 the  usual precaution,  so as to prevent an unequal con-
 traction.

  It should  be  observed that leather is tanned, or that the
 union between  tannin and jelly  is  much more  speedy  in
 summer than winter : This is in consequence of the heat's
favoring  the combination.  Upon reflecting on this, I was
led  to make an experiment of the following kind, which al-
though  imperfectly done,  from many circumstances, may
serve clearly to shew, that the tanning of leather may be
considerably quickened by means of heat.  In a very strong
solution  of tannin, I introduced a bit of hide,  and kept the
whole in an oven, the temperature of which was from i 30°
to 150° for thirty six hours.   On examining the leather it
appeared to me completely tanned,  so that I have not the
least  doubt but that the process might be surprisingly short-
ened, by means of artificial heat.  Tanners will therefore,
I think, find it to  their  interest to change, very materially,
their manner of operating, as well  as their places for the
process.   A small room, lined with a mortar of clay and
charcoal,  appears the  best  place, to have the hides intro-
duced in the solution of tannin.   Through this room, and
around the vessels  containing the  hides, small tin pipes
 should be arranged, so as to be connected with a small ket-
tle  that  may  be kept constantly boiling over  a little fire.
The  steam passing through would keep up a regular tem-
perature,  and  in all  probability complete the  process  of
fanning in 20 or 40 hours.   I sincerely wish this may be 
310
DISCOURSE X.
attended to by those whose circumstances will allow of maki
ing decisive and fair experiments.

   In  order to avoid the trouble of bringing bark to cities
where leather  is manufactured, it has  been proposed  to
prepare the decoction or solution  of tannin  in the forests,
and convey it to the  manufactories in casks.   This would
certainly be  an improvement.  Professor Woodhouse  of
Philadelphia, who  unlike most men, early commenced his
career of usefulness, ascertained that very great quantities
of tannin were contained in the  unripe juice of the per-
simmon tree,  so that at some future day he supposes it will
be an object to cultivate the persimmon tree, to yield tannin
for the manufactories.  The plant vulgarly called shoemake,
but more properly  named sumach,  has been  found to con-
tain immense quantities of tannin.   It grows very rapidly,
and it might be of great service to cultivate it as Well as
the persimmon tree, for the purpose of preparing decoc-
tions or solutions of tannin.
IV.  OILS.
   OILS exist in considerable quantities in  a variety  of
plants,  particularly in the seeds.   The qualities of oils are
so well  known, that it is useless to dwell on them.   Those
obtained from vegetables are divided into  two kinds,  the
one called  expressed or fixed oils, the other essential, vola-
tile or distilled oils. 
DISCOURSE X.
311
EXPRESSED OILS.
  THESE are generally obtained by strong pressure on the
seeds of plants.  They are thick, mild and inodorous when
pure ; but more commonly they are blended with the mu-
cilage of  the  particular plant, which  gives them odour,
color and taste.  The name of the oil depends on that of
the  plant from which it is obtained, and  there are a great
variety.   I shall only  notice three, which are in common
use, called olive, castor  and linseed oils.




                    OLIVE OIL.
  THIS is obtained from the fruit  of the  olive tree, by
mashing it under a  kind of millstone.  The past* formed
by this  is conveyed  under a plate, on which  a  large screw
is turned so as to produce a very  great pressure.  The first
oil is called virgin oil.   The paste is then moistened with
hot water and again pressed, when an  oil less pure is ob-
tained,  as it is mixed  with a mucilaginous matter,  which
has a strong tendency to putrefy, and render the oil rancid.
Most  of this oil of olives  of commerce is obtained from
Turkey : it  is used in  making soap,  and to season food
very generally.   Fifteen parts  of it  are  composed  of 12
parts carbon  and 3  hidrogen. 
312                DISCOURSE X-

                   LINSEED OIL.



  THIS oil is extracted from the seed of the plant linum,
commonly called flaxseed.  As the seed contains much mu-
cilage, it is roasted, or heated, before  it is put under  the
press.   This serves  to give the oil  a disagreeable flavor,  but
at the same time, it deprives it of the property of becoming
rancid,  and renders it one of  the most drying oils.  Hence
it is employed to form paints.
CASTOR  OIL.
  THIS is prepared as the above oil, from the seed of the
plant called ricinus communis, which should be kept warm
while under pressure.  It is prepared in considerable quan-
tities by some of the American farmers ;  and no doubt but
they will find it to their interest to cultivate the plant yield-
ing it much more generally.   In doses of about  an ounce it
is an excellent purgative.   Oil of  almonds, and indeed all
the expressed oils may be had by the above means ; it only
being necessary to subject  them to a proper mechanical
force.

  These oils combine with oxigen rapidly, so as to produce
inflammation if heated ; or  slowly at a low temperature,
so as to produce rancidity.  If exposed to the open air, they
slowly absorb oxigen;  this oxigen,  when it unites to the
mucilaginous part of  the oil, renders it rancid, and if the
oil be confined in a bottle  of oxigen air,  the rancidity is 
DISCOURSE X.                313
much more readily produced.   From this it must  appear
that the tendency of oils to become rancid, may be prevent-
ed, by depriving them of their mucilage ;  and this is actu-
ally done with great advantage in the preservation of olive
oil.  The mucilage is soluble in water, and  if the oils con-
taining it be well washed in warm  water,  they part  with
their mucilage,  and the oil can  afterwards be poured from
the surface  and  preserved  for years,  without danger of
rancidity.

   The  oil itself also  unites to oxigen, and becomes either
hard, or of a very drying nature.   On this is grounded the
art of painting with oils.   The  substances used to  give  a
color to bodies, depends on the whim of the operator.  This
substance  is  to be reduced  to  a very fine powder, and  is
then to be well rubbed up with the oil; commonly  linseed
oil is used.   The oil with the powder in it is to be thinly
and  regularly brushed over the body to be  painted.  The
oil then in part evaporates,  and  in part  abstracts  oxigen
from the air, and thereby becomes solid, so as to form a
coat or covering, which retains the coloring matter.  To
hasten the evaporation, the paint is frequently mixed with
some volatile substance,  as  spirit of wine and turpentine.
To hasten the union  with oxigen, it is common for  good
painters to boil their oils over  the metallic oxids, particu-
larly  those of lead  and copper.  In this case,  the oxids
part with their oxigen, which  unites to  the oil, and they
abstract a portion of the mucilage from the oil,  by which
the value of the paint is increased.
Rr 
314                DISCOURSE  X.

                 ESSENTIAL  OILS.
  OF the essential oils there is a great variety.  They are
named according to the plant yielding  them.  They are
characterized by a strong smell;  are soluble in ardent spirit,
and possess an acid and penetrating taste.  It is with diffi-
culty  that they can  be combined with the  alkalies,  to
form soap.

  The  essential  oil is sometimes distributed  through the
whole plant; sometimes in the bark, as in cinnamon.  Balm,
mint, and sage,  contain it in the leaves and stems.   All the
resinous trees contain it in their young branches ;  rosemary
and thyme contain it  in their leaves  and buds ;  lavender,
the rose,  camomile, lemon and  orange trees   in their
flowers ;  many fruits contain it in their whole substance, as
pepper, juniper, &c. oranges and lemons contain it in their
peelings, and anise and fennel contain it in their seed.  It
is to this oil  that the plants  generally owe their odour.

   In order to extract the oils, when they are contained in a
disengaged state in the receptacles of plants, they are sub-
mitted to pressure.  In this manner the oil or essences of le-
mons,  oranges, burgamot,  &c  are obtained;  but gene-
rally essential  oils are procured  by the  distillation  of the
substances contained  in it.  For this purpose,  the plants
containing the  oil, are put in a common  still,  of a small
size,  and sufficient water is added to cover them.   Fire is
applied and the oil rises, and is condensed in the condens-
ing worm of the still,  from whence it runs, and is received
and retained in stopped vessels for use.   When much wa-
ter comes over, and it retains some of the oil of the plant, 
DISCOURSE  X.               315
it is called the distilled water of the plant;  and when in-
stead of water, ardent spirit is used, then it is termed spirit
f the plant.

   The distilled oils are not so much employed in medicine
now as  formerly.  Many  of them are used chiefly as per-
fumes.   That obtained from the  distillation of turpentine,
and  commonly called  f-pirit of turpentine, is  prepared in
large quantities for the arts.   It is frequently used to adul-
terate the more valuable oils.  The fraud may be detected
by allowing  a drop to evaporate from the hand ; when  the
oils  are  adulterated with  fixed oils, it  may be known by
putting  a drop on white paper, which in that case  gives it
a greasy appearance.

   Essential oils are decomposed in a strong heat. If burnt,
more water  is formed during the process than when fixed
oils are burnt.  Hence they must contain more hidrogen,
to which they owe their volatility.   When allowed to be in
contact  with oxigen in a  low heat, many of them absorb
it, and are converted into solids of a resinous nature.



                    V. GLUTEN.
  THIS substance may be obtained by working or kneading
a quantity of dough, made of wheat flower, in water.  The
substance  which remains in the hand is gluten.   It has
been called a vegeto-animal substance,  in  consequence of
its strong tendency to putrefy, during which time it emits
ammonia, which shows  that it  contains  nitrogen.  It  is
elastic,  ductile, and seemingly fibrous in its texture.  It is 
316
DISCOURSE  X.
insoluble in water, and is  insipid; dried gently it is ren-
dered hard  and nearly transparent, and cracks with a noise
It is, while soft, frequently  used as a glue to cement pieces
of wood together which are not exposed to a moist air.   h
exists in a variety of vegetables, particularly in their seed -,
it is very nutritious to animals, and is composed of hidrogen,
carbon, oxigen and nitrogen.
VI.  FECULA.
  FECULA constitutes the  chief part of all the nourish-
ing grains and roots.   Barley consists almost ent.rely of it,
and great quantities are contained in  wheat, rye, oats, sago,
salep, potatoes, and innumerable other vegetable substances.
It is to this article that they owe much of their nourishing
qualities.   Fecula may be extracted from the  substances
containing it, in  a state of  purity,  by reducing  them  to
powder, and agitating them in  water.  The water, while
turbid,  is to be poured off, and  the fecula being suspended
in it,  gradually  falls to the bottom.   From this it may be
taken,  washed and dried.   It appears in the form of a light,
white, insipid, inodorous powder, insoluble  in cold, and
soluble in hot water, with which it forms a paste.

  When fecula is obtained in a  state of purity,  it consti-
tutes the article  commonly sold by the  term starch, which
is used in making pastes, hair powder,  &c.   Starch may
be extracted  from wheat, rye, potatoes,  or any substance
containing it, by allowing them to continue for sometime in 
DISCOURSE X.
317
 the water,  until  they part with it.   It  is also obtained
 from the husks of  corn and wheat.  The water suspends
 the finer parts of  it, and is to be poured off in that state.
•On standing  for sometime, the  starch is deposited,  but
 generally is of a yellow color.  To be freed of this, it is to
 remain in the water, until  the water turns sour; then it is
 to be taken out,  and  dried  and exposed  to the sun.

   The substances containing large quantities of fecula and
 gluten are used to make bread.   It is on the two, that the
 art of making it  depends; and it is to the two that bread
 owes its nourishing qualities.  The art of making fermented
 or loaf bread,  is of  great  importance, and is of very anci-
 ent date.  The substance  best  adapted for making it, is
 wheat flour.   Of this,  three parts  should be  mixed with
 two of  water, so as to form a  paste, which must be well
 kneaded with  a  small quantity of yest.  This is then to
 be allowed  to  rest  in a place, the temperature  of which
 being from 70° to 80°.  In two or three hours the dough
 begins to change:  carbonic acid  is formed, which not pas-
 sing through the  paste, causes it to rise, or swell in all di-
 rections.  This is  called* the panary fermentation.   After
 four or  six  hours,  the  dough  is  then to  be  made  in
 loaves, and baked  in ovens, the heat of which the bakers
 judge of, by letting  fall a little flour, which when the heat
 is not too  high,  turns black,  without burning.   The heat
 of  the oven dilates  the  carbonic acid,  which  causes the
 loaves  to rise still more until the crust is formed,  which
 prevents any further alteration in size: then the particles of
 dough,  having exercised the affinities peculiar to them in a
 high heat, or having baked, the bread is withdrawn from the
 oven. Generally durincr  the  baking,  the  h'^d Irr-s. n«*
 fifth of  its weight,  from the evaporation  of water; and
 this evaporation will continue sometime  afterwards, un-
 less the  bread  be  included in wet cloths.   After baking, 
318
DISCOURSE  X.
the proximate principles of vegetables,  gluten and fecula,
cannot be distinguished in the bread.

  The excellence of wheat bread over all others,  appears
to depend on  the happy combination of the fecula and glu-
ten in wheat.  However, very good bread may be made,
by exercising a little art, from other vegetable substances.
Rye flour makes a tolerable good bread alone.   It  may be
much improved by combining with it a little barley flour,
as this last contains more fecula than the rye,  and less glu-
ten, of  which the rye has too much.  Potatoes also make
a very good bread, provided they are freed of a little mu-
cilage, of which they contain too much.   For this purpose,
the potatoes are to be rasped, or reduced to  small  pieces,
and then washed  in water.   The water dissolves the muci-
lage,  and is to  be poured off, and the potatoe flour dried.
Potatoes previously boiled  and mashed with a rolling pin,
are then to be mixed with an equal quantity of this potatoe
powder and baked. The bread formed  will be found very
agreeable.  Perhaps it would be as well to add barley flour
to the potatoe dough as the potatoe powder.
VII. INDIGO.
  THE valuable stuff dye, called  indigo, bears a faint re-
semblance  to  starch, and  has therefore been sometimes
classed with it; but its properties are sufficiently remarkable
to distinguish it from all other substances, and  its import-
ance entitles it to  a distinguished place among vegetable
principles.   It is  commonly  procured by the  following
process: 
DISCOURSE  X.
3191
   The plant which  yields it, is the indigo-ferra tinctoria,  a
shrub which is cultivated for that purpose,  in  Mexico and
the West India islands.   When the plant has  reached ma-
turity, which  requires about six months,  it is  cut  down
and placed in wooden vessels of a large size, and  covered
with  water.   In this  situation, when the temperature is
about  80°, a  kind  of putrefaction or fermentation com-
mences, and goes on rapidly.   The water soon has a  green
appearance;  a smell resembling  the  volatile alkali  is ex-
haled, and bubbles  of carbonic  acid are emitted.  When
the fermentation  has continued sufficiently long, which is
judged of by the  paleness of the leaves, and which requires
from  six to twenty-four hours, the liquid is poured off into
large  flat vessels, where  it  is constantly  agitated till blue
flakes begin to make their appearance ; a little lime water is
now poured in, which causes the blue flakes to fall to  the
bottom.  The  yellow liquid is decanted off,  and the blue
sediment  poured into linen bags.  When the water has
drained from it sufficiently, it is formed into  small lumps,
and dried in the shade, in which state it is  exported  and
sold under the name of indigo.

   Unless  the fermentation take place,  the plant does  not
yield  indigo; and it is stated that the contact of air is  ne-
cessary also.   The  separation of carbonic acid shows that
chemical  changes are wrought; and the use of the lime
water seems to unite to the acid,  which prevents the  preci-
pitation of the indigo.

   Indigo  is yielded by several plants.   Dr. Roxburg first-
drew the attention of manufacturers to the merium-tinctori-
um, a tree very common in Indostan,  from  the leaves of
which indigo may be extracted  in abundance by a short
process.  The leaves are kept in a copper full of water,
supported at the temperature of 160°, till they assume a 
320
DISCOURSE  X.
yellowish hue, and the liquid acquires  a  deep green color.
The liquid is then drawn off, agitated in  the usual manner,
and the indigo is precipitated as above,  with lime water.

  Indigo may be obtained from a plant, growing wild in
many places, called  woad.  When arrived at maturity,  it
is cut down, washed and hastily dried  in the  sun, ground
in a mill, pkced in heaps,  and allowed to ferment for  a
fortnight.   It  is  then well mixed, and made into balls,
which are exposed to the wind and sun  until they putrefy
and  emit the volatile alkali.  The woad then  falls to  a
powder, and is  sold as a dye stuff.

  Indigo is  a fine  light friable substance,  of a deep blue
color.   The lightest is the best; but it is always mixed with
foreign substances,  and the purest of commerce seldom
contains more than 50 per cent, pure indigo.  It has neither
taste  or  smell.   It  is neither changed  by water  or air.
When heated it emits a blueish red smoke, and burns away
with a faint white flame.   The  alkaline  solutions act upon
indigo when it is precipitated from a state of  solution,  and
render it of a green  color.

   The action of the acids upon indigo has been  examined
with most attention, and they certainly produce most re-
markable effects.  Concentrated  sulphuric acid dissolves it
readily.  Eight parts  of sulphuric acid,  when mixed with
one of indigo,  dissolves the indigo in twenty-four hours.
The solution of indigo is well known by the name of  liquid
blue.   While concentrated  it is  black,  but when  diluted
with water  it assumes  a fine deep blue  color,  and a drop of
it will color several quarts of water.

   From experiments which have been made, it is ascertained
that all those substances which have a very strong  attraction 
DISCOURSE  X.
321
 for oxigen, give a green color to indigo, and at last destroy
 it.  Hence it is extremely probable, that indigo owes its blue
 color to oxigen, and that it becomes green by parting with
 its oxigen.  It is only when green,  that indigo is in a state
 capable of being held in solution by lime, alkalies, &c. in
 which state it is applied as a dye to cloth.  The cloth, when
 dipped in  the  solution  of it,  combines  with it,  and the
 blue color  is  acquired by  exposure to the atmosphere;  or
 dipping it in  oxi-muriatic acid,  by which  it   unites  to
 oxigen, and soon acquires  a blue color.   Sulphureous acid,
 the vegetable acids, and sulphate of iron, (copperas) give
 the liquid blue a green color, by abstracting oxigen.

  By  the decomposition of indigo  by means of heat, it
appears to be  composed  of oxigen, carbon, hidrogen and
nitrogen.
StSSiSSS
s« 
DISCOURSE  XI,
     VIII. SUGAR;

            OR

SACHARINE MATTER.
  SUGAR, which at present forms so important an article
of our food, seems to have been known at a very early pe-
riod to the inhabitants of India and China:  but it was only
during the crusades that it was brought from the east, and
distributed in considerable quantities in the northern parts
of Europe.  At first it was used only as a medicine.

  Sugar, or sacharine matter, exists in a great number of
vegetables.  It is  afforded in largest quantities by the sugar
cane, and by the maple and birch trees.  The roots of se-
veral plants, particularly the beet and parsnip,  contain it in
lesser quantities,  as well as the fruit of many plants, as
grapes,  persimmons, cherries, sweet apples, and indeed all
the variety of  vegetable substances which excite the sense
of sweetness in the mouth. 
DISCOURSE  XI.
323
  The sugar of commerce  is usually procured from the
juices of the sugar cane, for which purpose it is cultivated
in the East and West Indies.  The method of making it is
exceedingly simple,  and does not require an expensive ap-
paratus.   About  the end  of May,  they plant the  cane
under favorable circumstances, attend to its  growth, and in
January or February following they  are cut down, at which
time they are about ten feet high, and one inch in diameter,
and have not flowered.  The canes  are now passed through
the rollers  of a mill, which press the juice out in vessels
prepared for its reception.   Three quarts of this juice ge-
nerally contain one pound of sugar.  To extract the sugar
the juice is then conveyed to pots properly adapted for the
purpose, and boiled  in lime water till its consistence is  in-
creased.   During  its boiling, such impurities as arise  on
the surface are skimmed off.   A quantity of blood, towards
the last of the process,  is added by some manufacturers to
free it from some of its impurities.   The blood acts entirely
mechanically; it  is  diffused through the mass, and when
heat is applied it coagulates,  and carries with it many imr
purities.  The lime acts by neutralizing the oxalic and other
acids.   The sugar, after  repeated  solution in water, and
evaporation, is poured into moulds, where it  crystallizes,
and in that state is sold in commerce.   Its  purity  depends
on the care taken in these processes ; and as this varies,  we
have  the  sugar either  black, brown, refined  and white.
Such parts as are found not disposed to crystallize readily,
are sold under the name of molasses.

   In the West India islands the raising of  sugar is much
more expensive, which arises from the nature of the soil,
and  from the price of labor.  It is obtained from the culti-
vation of the cane altogether there also.   But in this coun-
try, the farmers procure sugar in several parts for their own
use, from the sap of the sugar maple tree, which abounds in 
324
DISCOURSE  XI.
the woods.  It reaches maturity in about twenty years, and
is then from two to three feet  in diameter.   In February,
March and April, the tree is bored with an augur on the
south side, to  the depth of about three  fourths of an inch,
in an ascending direction, and then it is made  two inches
deep.  A wooden spout is introduced in the hole, through
which the juice flows for five or six weeks.  When it ceases
to flow from  the south, an orifice is opened on the north
side, when more sap is obtained.   This  process improves
the trees.  Each of them generally yields from twenty to
thirty gallons  of sap, from which are made  from five to six
pounds of sugar.  The sap should not  be kept longer than
twenty-five hours after it runs from the tree.   It is usually
put in kettles  ; to each fifteen gallons of which a spoon full
of lime, the white  of an egg, and some new milk is added,
when the evaporation is  carried on as above, and also the
 subsequent purification.

   In  Europe considerable quantities of sugar have been
 obtained from the beet: and for this purpose it is cultivated in
 soma parts.   The method of extracting sugar from it, is to
 free the beet  of its heart, and  then boil it and press out the
 juice, or press out the juice without boiling it, as some ad-
 vise.  This juice is then to be strained in woolen cloths, and
 evaporated as the  other juices which  yield sugar.  It is
 stated that some beets have yielded one sixteenth  of  their
 weight of sugar.   This sugar is not at present much used,
 as it is found to contain something which gives it a  disa-
 greeable, nauseous taste:  when freed of  this,  it will be as
 voluble as any, and  no doubt  but that  in time the beet will
 be  cultivated for the purpose, at least in countries whose
 commerce is destroyed by war.

    The properties of sugar are well known.   It is very so-
 luble in water, particularly when the water  is hot.  In this 
DISCOURSE  XI.
325
state it unites to any quantity, and forms  syrup.  To ardent
spirit it  also  unites, but not in such considerable quanti-
ties ; when heated, it does not combine with moi e than one
fourth its weight.   It is one of the most nutritious substan-
ces known.   In a high heat, without the contact of  air, it
melts, and if allowed to crystallize, it forms  candy.   A  va-
riety of  vegetable substances, when boiled in the syrup,  are
enabled to resist putrefaction;  and on this is founded  the
art of making conserve.  When sugar is exposed to  a high
heat it burns, and carbonic acid and water are formed.  Ac-
cording to Lavoisier, it is composed of 8 parts hidrogen, 2S
carbon and 64  oxigen.

   Honey is also a species of  sugar, blended with a muci-
lage, to which  it owes its peculiar taste.  It is extracted by
bees, from  a variety of  flowers in which it lies exposed to
the air.   It generally retains the peculiar flavor of the plant
from which it is taken.  The purest kinds are obtained from
northern countries.   In  its nature, it seems more nearly al-
lied to molasses than to common sugar ;  and  like molasses,
is used in some families, not only as an article of diet,  but
to preserve vegetables, as apples, peaches and  quinces.

   It seems  that sugar is frequently formed in animal parts,
as in the kidnies of men, during the disease called diabetes;
and also during the action of heat on some vegetables.  Some
apples  frequently become sweet while baking ;  and  fecula,
during  its conversion to malt,  also acquires  a  sweet taste
 from the formation of sugar.   No doubt but that sugar will
 always be formed, when its constituents are  present in due
 proportion, and those circumstances are created, which are
 necessary for their action on each other.  What these neces-
 sary circumstances are, cannot now be determined, and per-
 haps never will. 
326
DISCOURSE  XI.
  Sugar is remarkable for  a change which under certain
circumstances it undergoes, termed, the vinous fermentation,
by which a liquor is  produced of an  intoxicating quality,
called, commonly, ardent spirit, when distilled ;  and by the
chemists, alcohol.  For this fermentation  of sacharine mat-
ter, or spontaneous motion, as some call it, there must  be a
certain degree of fluidity and heat.   The products are found
to vary, in some measure, with the qualities of  the articles
employed.   On  this  is  founded the difference  between
wines, beer,  cyder, perry, and indeed all the other products
of fermentation, which possess an  intoxicating property,
which they owe to  the same substance; namely,  ardent
spirit or  alcohol.

   If a quantity of sugar be  added to ten times its weight of
water,  or if  any sweet vegetable juice be taken  in its stead,
and  placed in a situation  the temperature of which conti-
nues from 65° to 85°; it  first assumes a turbid appearance;
bubbles of  air arise and  escape with  a hissing  noise;  a
froth appears on the surface; heat  is given out; the sweet-
ness is gradually lost, and in three  or four days a particular
pungent  taste is acquired; the fluid deposits a sediment
and becomes again clear and transparent; it has now acqui-
red  a brisk lively appearance, and a vinous odour.  When
drank, it exhilirates the  spirits; when poured  out  of the
vessels containing it,  a froth appears, arising from the es-
cape of carbonic acid air;  when distilled, it yields the sub-
stance called ardent spirit in common language; and when
exposed to the air,  it is capable of being converted into
vinegar, or the acetic  acid, as before observed.

   During this process, the  sugar is constantly diminishing,
and is finally completely decomposed : one part of  it sepa-
rates in the form of  carbonic acid;  and the remaining  part,
a little  carbon and  much  hidrogen, chemically combine 
DISCOURSE  XL
327
together and form alcohol; the intoxicating, or spirituous
liquor.  The process seems somewhat analogous to  com-
bustion, as is evident from the evolution of heat,  and for-
mation of carbonic acid.
WINE.
  THIS product of fermentation, is obtained under circum-
stances like the above, from the expressed juice of the grape.
The grapes are put into a  vessel, when the temperature is
about 50° after they are bruised and much agitated.  Then
fermentation is excited, and the before mentioned appear-
ances take place.  When the fermentation ceases, the wine
is drawn off from  the  lees into casks, where it undergoes
a second,  though insensible  fermentation, which more in-
timately developes its  principles,  and  it  is this  change
which causes the difference  between the old and the new
wines of the same kind. -

  The  properties  of  wine  differ very much  from each
other,  these depending on  the nature  of the particular
grape,  and the manner in which the process is conducted.
These differences are known by all who  drink wines.  All
the various wines contain more or less of the following in-
gredients,  not to mention water, which  constitutes a very
great proportion of every wine.

   1. An acid.  All wines give a red color to paper stained
blue, and of course contain an acid.  The malic, citric and
tartareous acids are very generally met with in them. Such
as have the  property of frothing, owe it to carbonic acid. 
328
DISCOURSE XI.
These wines are usually weak,  their fermentation proceeds
slowly, and they are put up in close bottles before it is over.
Hence they retain the last  portion of carbonic acid which
were evolved.

   2.  Alcohol.  All wines  contain more or less of this intox-
icating spirit,  and in proportion  to the  quantity  is  the
strength  of the wine.  From one fourth to one fourteenth
of the wines is usually alcohol;  and it can only be  sepa-
rated by  distillation.   It is then called brandy.   The quan-
tity  depends on the quantity of sugar in the grape juice.

   3. Extractive matter.  This exists in all new wines ;  and
it is to this that they owe their  power of undergoing the
acetous fermentation.  The quantity of it diminishes  with
the  age  of the wine, as it is gradually  precipitated from
the  wine while at rest.

   4. Oil.  Every  wine is distinguished by a peculiar flavor
and odour, which probably depends upon the presence of
a volatile oil,  so  small  in  quantity  that it cannot be de-
tected.

   5. The  coloring  matter, is derived from  the  husk of the
grape,  and  is not dissolved till the alcohol  is developed.
This matter is analagous  to the other coloring matter of
plants.   It may be precipitated if the wine be exposed to the
heat of the sun.   It is sometimes lost  by age,  and it  may
readily be destroyed  by a  little  lime water.   Perhaps the
husk of grapes would answer well for coloring all spirituous
 drinks.

   Before dismissing  the subject of wines it may be remark-
 ed,  that the sweet  taste of the sweet wines arises from a
 quantity of sugar they contain,  which was not fermented. 
DISCOURSE  XI.
329
In some instances  a  little sugar is added.   In others the
adulteration is  greater, and the entire qualities of the wine
are altered, or imitated by innumerable arts.  The red wines
are frequently  adulterated with sugar  of lead and alum.
The first article may be detected by adding a little sulphu-
ric acid, which unites to the lead, forming an insoluble com-
pound.   By adding the sugar of lead to the wine containing
alum, the same compound will be formed.

  By processes similar to the above, the juices of gooseber-
ries, apples, pears, persimmons, cherries,  &c. may be made
into drinks equally pleasant,  in the opinion of good judges.
They are  generally improved by  evaporating part of their
water,  by boiling  before fermentation.   The same advan-
tage will be derived by adding a little sugar to them, and it
is  much to be wished that more attention was paid to  the
preparation of these drinks, as it would supersede the use of
imported articles of the kind.
PORTER;
    or
  BEER.
  PORTER is made of the first quality in London,  by
Mr. Biley, in the following manner: Barley is first reduced
to malt by  being steeped in warm  water for five or six
days;  it is then drawn off, and the barley is spread upon
the floor, about six inches thick, when it begins to germi-
nate,  which  is allowed to continue until the sprout is two
thirds  or three fourths of the length of the grain.   When 
330
DISCOURSE  XI.
this is accomplished, the grain is spread thinner, and turned
over twice 3 day for several days; it is then transferred to
the kiln, heated with wood,  and dried  till  it acquires a
brown color;  it is then called brown malt.  From this malt
porter is brewed in the following manner:

   A  quantity of malt,  freed from its  germ, is  coarsely
ground and put into a vessel  called  the mash tub.   Water
heated from 160°  to 180°, is poured on it, and the whole is
stirred intimately together, either by machinery or the hand,
so that the soluble part may be extracted.   When this ope-
ration is  over, the  liquor called  the extract, is drawn off.
Another infusion is then made by means of water of a higher
temperature,  which  of course  is weaker than the former,
and these are either mixt  or kept  separate.   Both have a
sweet taste ; they contain the sacharine, the extractive, and
the  glutinous parts of the grain.   The  infusion thus ob-
tained is called wort.  It  is then boiled with hops, to give it
a certain  aromatic bitterness,  and to render it less  liable to
spoil in keeping.  It is then cooled as expeditiously as pos-
sible in very  large shallow vessels, called coolers,  in which
it measures only one or two inches  deep.   As soon as it is
cooled  it is put  in  the fermenting  tub,  with a little yest,
(which is nothing more than  the  same article fermenting)
and the whole is suffered  to ferment.  When the fermenta-
tion has advanced to a due  degree, and the yest ceases to
rise, the  beer is divided  into smaller casks to facilitate the
separation of  the  yest; and lasdy, it is conveyed into bar-
rels, and  kept in  cool places, with the precaution  of sup-
plying the loss it  suffers by evaporation.   Eight bushels of
malt and ten pounds of hops  produce,  upon an  average,
one hundred gallons of London  porter.

   The grains  of rye, Oats, corn, and many other vegetable
matters,  which either contain  sugar,  or the ingredients 
DISCOURSE  XI.
331
 which may be converted  into sugar, are  frequently em-
 ployed for making beer. , Their strength is increased, by
 adding molasses or sugar.   They should all be kept in tight
 vessels, after properly fermented, to prevent their becoming
 dead, to use a common phrase, or to keep them  from part-
 ing with their carbonic acid or fixed air and spirit.

   When honey is blended with  water,  and allowed to fer-
 ment as above, it retains a peculiar flavor, and the drink is
 called mead.

   But whatever be the peculiar nature of these various fer-
 mented drinks, they all contain what is called ardent spirit;
 and  it is to  this that they owe their intoxicating quality.
 They all yield it when subjected to distillation in the usual
 way.   This spirit  is formed  by a change in the  chemical
combination of the constituents of sugar.  This chemical
change arises  from  a certain state, created by water and
heat,  in which those affinities of the substances peculiar to
that  state are  exercised,  in  proportion  to the quantity of
 the substances present.  The yest quickens or promotes this
change, as the same fermentation is going on in it, by which
the particular state for the  chemical change is communi-
cated to the rest of the  mass.
ARDENT SPIRIT,  ALCOHOL;
                OR
      SPIRIT OF WINE.
  AS before observed,  when the fluids which have under-
gone the vinous fermentation  are  distilled,  there comes 
332
DISCOURSE  XI.
over a substance called commonly ardent spirit: by the che-
mists the term alcohol is applied to it when in a state of pu-
rity.   To obtain it pure, it is necessary to subject it to re-
peated distillation; when this is done,  it is found colorless,
possessed of  a penetrating odour,  and  an  intoxicating
quality when  drank  in but small  quantities.   It is capable
of being  inflamed  without  a wick,  and  burns without
smoke.  The  products  obtained by  its combustion  are
water and carbonic acid,  which shews that like essential
oils, it is composed, of carbon and hidrogen.   It is very vol-
atile  and consequently  evaporates  spontaneously  at  com-
mon  temperatures.   It  boils at  176°.  It  combines with
water,  sugar,  resins, the  alkalies,  essential oils,  cam-
phor, &c.  It resists the putrefaction of several vegetable
and animal substances, when they are immersed in it.

  The ardent spirits in common  use, are very far from
being pure.   They all retain the  particular qualities of the
vegetable substance from  which  they are procured,  as
well as a considerable quantity of water, from which, they
can only be freed by frequent and cautious distillation.—
The flavor,  it is  well known, of the grape, apple, peach
and persimmon, exists in the brandy, which  is formed from
each  of them ; of the rye, in  whiskey; of the juniperberry ,
in gin; of  the cane,  (or  molasses) in rum, &c.   The
strength depends  on the quantity  of alcohol  in them.   The
parts which first  come over during distillation, are always
purest or strongest.   In order to judge of the degree  of
purity or strength of the spirit, several methods have been
proposed.  They are all however  fallaciou ,  excepting that,
by which the specific gravity is ascertained.  When the liquor
is perfectly pure,  as  in  spirit of  wine repeatedly  distilled,
the specific gravity is 0.800; but  it is seldom found so pure.
The specific gravity of the alcohol of  commerce, is seldom
less than 0.8371; it  is scarcely necessary to remark,  that 
                   DISCOURSE  XI.                333
the increase of specific gravity is always proportionate to
the impurity of the spirit.  When it is not convenient to
weigh the spirit with proper caution to ascertain its specific
gravity, an idea may be judged of it by using a phial, which
when empty, sinks into pure water to a certain height.   On
filling it  with  the spirit, and introducing it in water,  the
degree to  which it sinks, will indicate the specific gravity of
the spirit.  In measuring spirit,  it should always be recol-
lected that it is  much expanded by heat.

  There have been many attempts made to purify  or  in-
crease the agreeable  qualities of the  spirituous liquors in
common  use, by  making additions  to  the  usual  mode of
procuring them.   It  seems  in  some instances  to  be an
improvement to the spirit, to  let it  pass through  pounded
charcoal,  or to distil it with this substance.   In  some in-
stances, the spirit is mixed with an alkali, then on  distilling
it, a  little nitric  or  sulphuric  acid is  added,  by  which
means a little ether is  formed, which is supposed to  in-
crease the good qualities of the liquor.   These liquors may
be colored, by burnt sugar,  the  husks  of grapes, or  any
coloring matter not injurious to life.
ETHER.
  ALCOHOL unites to the oxigen of acids under certain
circumstances, and forms the very odorous, volatile, pungent
and inflammable fluid, called ether.  The qualities of  this
ether are  somewhat  influenced  by  the  particular acid
which is added to the alcohol.   This  has given rise to  the 
334
DISCOURSE  XI.
differences in  the names of the ether, which are called ac-
cording to the acid employed, as the sulphuric, nitric, acetic,
muriatic and phosphoric ether.
SULPHURIC ETHER.
  TO prepare this ether, any quantity of  sulphuric acid is
graduslly mingled with an equal weight of alcohol in a re-
tort, connected by a tube to a receiver, which is kept cool.
Heat is  applied to the retort,  and a colorless fluid rises and
condenses in the receiver.  When the distilled fluid amounts
to about half the quantity of spirit employed, or when the
ne^k of the retort becomes obscured with white fumes, the
distillation is to be stopped.   A thick black liquid remains
in die retort.  The distilled liquor, which is the ether, im-
pure from the admixture of water and sulphureous acid, is
t • be mixed  with a  little potash,  and again subjected to
c filiation by a gentle heat, when it comes over in a state
o  purity.
NITRIC ETHER.
  THIS may be prepared in the  following manner : Two
parts of alcohol are poured in a strong glass bottle provided
with a ground stopper, and placed in a cold mixture, where
the temperature is below the freezing point.  One part and
a half of nitric acid,  also made cold,  is  to  be cautiously 
DISCOURSE  XI.               335
added  drop by drop,  and at intervals sufficiently  long.
When  the mixture is completed,  the glass is for some time
left in  the cold,  and well stopped.   After  this, the ether
is  found swimming on the surface, from which it is to be
carefully taken off; and to have it more pure, it may be
cautiously distilled upon a little potash.
       ACETIC  AND PHOSPHORIC ETHER

   MAY be obtained by distilling equal parts of the strong-
est acids of these  kinds with alcohol, and proceeding as in
the first instance.   No  good method of obtaining muriatic
ether  is known, as the  methods recommended do not fur-
nish a fluid possessed of all the properties of ether.

   It is onlv the sulphuric and nitric ethers which are fre-
quently nude.  They are chiefly used as a medicine  in re-
peated doses of two or three tea spoons full in low  fevers,
particularly of the nervous kind.   They are also employed
to dissolve a few  substances in the arts.
IX. GUM.
  HAVING now considered sugar and the modifications to
which it is subject, we proceed to the consideration  of the
next vegetable principle,  which is gum, or mucilage. This
is  found in all young plants, and often exudes spontane-
ously from certain trees,  as  the cherry, peach and plumb
trees.  The gum arable of the shops is obtained  from the 
336                DISCOURSE XI.
 tree called the mimosa nilotica; large quantities of gum exist
 in the seeds of some plants, as quince, water mellon,  and
flax seed, from which it may be extracted by hot water ; as
also  from the bark of the elm,  from marshmallows,  &c.
Gum,  when dried, is void of odour and taste  ; is not fu-
sible or  volatile, is  very  soluble in water, but not  in al-
cohol.   With  water it forms an adhesive paste.  It is very
nutritious to animals, and  is consequently used  as an article
of diet in some places.  More generally it is employed in
the arts.   When subjected to a high heat, it yields products
showing  it to be  composed of oxigen, hidrogen, carbon,
nitrogen  and lime.
X. RESIN.
   THIS is a substance also met with in considerable quan-
tities in vegetables, particularly in the wood, bark and roots
of trees.  It maybe extracted from them, by infusing them
in ardent spirit,  which is afterwards to  be evaporated; but
a number  of trees suffer it to exude through them as gum,
from whence it is collected in a tolerable state of purity.


  The properties of pure resins are as follows: They pos-
sess a small degree of transparency, and a color generally
inclining to yellow.   When exposed to heat, they melt,
and if in contact with oxigen air they burn, emitting at the
same time much smoke. They are insoluble in water, but are
very soluble in alcohol and oils, particularly in the oil of tur-
pentine; and when in  solution, they are used for varnishes. 
DISCOURSE XI.
337
   The  resins obtained from plants are  almost universally
 mixed with other substances to which they owe their taste
 and odour; though  when pure,  as in copal and sandarach,
 they  are  nearly  insipid and inodorous.   Their effects on
 animals are considerable,  and many of the vegetable reme-
 dies  owe  their activity to the resin they contain,  as aloes,
 scammony, &c.   However, as those substances which con-
 tain most resinous matter possess nearly the same properties,
 it would be useless to dwell on each of them.  The most
 distinguished  of  the   resins, are  rosin, copal,  sandarach,
 mastich,  elemi,   dragons blood,  and the several  turpentines
 and balsams.

   Rosin is obtained from different speties of fir, as  the
pinus abies, sylvestris,  larix  and balsamea.   It  is  well
 known, that a resinous juice exudes from the pinus sylves-
tris,  or common  scotch  fir,  which  hardens into tears.
These tears constitute the substance called thus, or common
 frankincense.  When a portion of bark is stript from these
 trees, a liquid juice flows out, which gradually hardens.—
 The juice has obtained different names according to the plant
from which it comes.   The pinus sylvestris yields common
 turpentine;  the larix, Venice  turpentine;  the balsamea,
 balsam of  canady,  &c.   All these juices, which are com-
 monly distinguished by the name of turpentine,  are compo-
 sed of two ingredients; namely, oil of turpentine and rosin.
The  oil is separated by distillation in common stills; great
 care  being taken not to have the  heat too strong, and to
 keep the condensing tube very cool.  When  the oil is  dis-
 tilled, the rosin  remains  behind.   When  the distillation
 is  continued  to dryness, the  residuum  is  known  by
 the name of common  rosin;  but when water  is mixed
 with  it,  while  yet fluid, and well  agitated,  the mass
 is  called yellow  rosin.   The yellow rosin made by melting
                          Uu 
338
DISCOURSE  XI.
and agitating this substance in water, is preferred for most
purposes because it is more ductile, owing probably to its
containing a little oil.

   Common tar may be considered as somewhat allied to
turpentine.   It is obtained by burning the pine trees, par-
ticularly the roots, in a place covered in  great measure with
earth ;  so that the combustion is very slow, and in conse-
quence  of this, the  resin  melts,  acquires a  black  color
from the combustion, and runs out at orifices, made in  de-
pressed parts for the purpose.  From  this it is taken and
put in barrels and sold for the numerous purposes of com-
merce.   The tar when boiled, parts with its oil, to which
it owes its fluidity, and is  then converted into pitch.  Per-
haps it  would  be of some advantage at  ship yards where
 much pitch is made, to have contrivances for the purpose,
by which all the oil might be saved during the conversion
 of the tar into  pitch.   Tar is also  used in the  healing  art.
 When mixed with fat, it  forms an excellent ointment for
 the disease called the scalled head.  Water digested on it
 for sometime, (called tar water J has been drank by patients
 laboring under debility with advantage.
OF VARNISHES.
  RESINOUS substances form the base of all varnishes.  A
coat of varnish ought to resist the action of the air and
water, and not change such  colors as are underneath; it
should be easily spread over  the whole surfaces of bodies,
without leaving cavities or pores;  and it should not crack
                          X x 
DISCOURSE XI.
339
 sr scale  off.   Resins are the only substances possessed of
 these properties.

   To form a varnish, resins must be most intimately blend-
 ed,  or rather must be dissolved in some fluid, so that they
 may be properly applied to the surfaces of bodies.   They
 are  usually dissolved  in expressed  and essential oils,  and
 alcohol, forming the kindsof  varnish, called the oily; essen-
 tial, and spirituous varnish.

   Before the oily varnish is made, the oil should be boiled
 over litharge, or any of the metallic  oxids; by which,  they
 unire to oxigen, and acquire a strongertendencytoevaporate
 and become hard.   The evaporation is usually quickened
 by the addition of a little oil of turpentine.

   The essential varnish is usually formed by dissolving the
 resin in the oil  of turpentine.

   The spirituous varnish is formed by dissolving the resin
 in ardent spirit.  This varnish is subject to cracking  when
 applied,  to prevent which,   a  little oil of  turpentine is
 added, which also increases its lustre,  The best kinds are
 made of the resins called copal,  sandarach and mastich.

  The copal varnish is deemed by far the most valuable: the
copal is obtained from a tree growing in the North and South
 America.  It  is a beautiful transparent resinous like sub-
 stance, with a slight  tinge  of brown.  When heated,  it
 melts  like other resins;  but  it differs  from  them  in  not
 being  soluble  in oils  of turpentine and alcohol, without
 particular management;  nor  does it unite with the fixed
 oils as readily as the other resins.   When it is kept melted
 till a sour smelling aromatic odour has ceased to rise from
 it,  and then mixed with an equal  quantity of linseed oil 
340
DISCOURSE  XI.
 which has been deprived of all color, by exposure to the
 sun,  it unites to the oil, and forms a varnish which  must
 be dried in the sun.  If it be desired to dissolve the  copal
 in oil of  turpentine or alcohol, it is necessary that the heat
 should be above the boiling point, which can be made so,
 by heating the articles in  a strong covered vessel.  Or in-
 stead of  this,  it has been proposed to dissolve the copal  in
 the steam of  these  solvents,  by causing  them  to  boil  in
 closed vessels, while the copal is suspended just over them,
 where it melts and is dissolved.  It forms  a  colorless var-
 nish, which maybe applied without injuring  the colors un-
 derneath.

   To increase the lustre  of varnishes after the solvent  of
the resin is evaporated or dried, they are rubbed with pound-
ed pummice  stone and water;  then  they are rubbed dry
with an oiled  rag.  The surface is  cleaned  of  all  oil, by
rubbing it with soft linen rags, with a little starch powder,
and then with  the clean palm of the hand.
BALSAMS.
   SUCH  resins as  spontaneously issue from  their plants,
 owe their fluidity to an ethereal oil which is combined with
 them, as  also their fragrant  smell.   While they  retain
 this oil,  some of them are called balsams; and all the bal-
 sams  of  the shops may be considered as resins dissolved in
 an  oil.   These most generally met with, are  the balsams
of Capaiva,  of Peru and of Tolu.   These like most  of
the resins  are procured by making  incisions in  trees, and
Collecting the juices  in proper vessels, where they are cp- 
DISCOURSE XL
341
vered to prevent the evaporation of this oil.   These are oc-
casionally used in medicine as a stimulant to the kidnies,  m
small and repeated doses of from ten to thirty drops.

  There is a chemical combination of  certain proportion of
resin with gum, forming  compounds called  gum-resins.
These compounds possess the property of dissolving equally
well in ardent  spirit and water.   The most remarkable  of
these are the substances of  the shops, called gum, galba-
num, gum myrrh,  opium, gum asafoetida,  &c.  They ex-
ert more action on animals than  any pure resins or gums :
and  when dissolved in spirit constitute the tinctures of the
shops,  as the tincture of aloes,  tincture of opium or laudV
num, &c.
XI. EXTRACT.
   EXTRACT exists abundantly in the juices of all plants.
It is soluble in water, ardent spirit, and in diluted acids.
It may be obtained from plants by macerating them in water,
and then evaporating  it by a moderate  fire.   When  the
temperature is at  the boiling point, and the extract is in
contact with the air,  it unites to oxigen, forming an  insi-
pid substance no longer soluble in water ; in which respect
it differs from  gum-resins.   Many of the  medicines owe
their virtues to this extractive matter, from which it is ob-
tained by infusing them in water: of this  kind are the ex-
tracts of Peruvian bark, of opium, of liquorice, &c.  They
should  be covered from the air, while making,  to prevent
the absorption of oxigen,  which destroys their virtues. 
342               DISCOURSE XI.

                12. ELASTIC  GUM;

                          OR

                  CAOUTCHOUC.
  THIS is a part of some plants remarkable for its elasti-
city when dried.   It is  principally obtained by puncturing
certain  trees of  South  America,   called  the caoutchouc,
and xhejatropha elastica. It exists also in the misletoe, in gum
mastich, and in various plants.  It is first thick and milky,
and becomes hard on exposure to air.   It can be stretched to
a considerable extent without breaking, and when the force
is withdrawn it immediately contracts.  The blackish color
of the caoutchouc or Indian rubber of commerce, is owing
to the method of  drying it.    It is soluble in ether and vo-
latile oils.   It is  softened but not dissolved by water.   It
is insoluble in ardent spirit, and it loses its elasticity by heat.
It is chiefly  employed in the arts for making bottles, cathe-
ters, &c. for which  purpose it is previouly dissolved in e-
ther, and then  applied  to the  skeletons of the  vessels,
when the ether evaporates.  Its elements are carbon, hidro-
gen, oxigen, and nitrogen, as  will appear by the products'
it yields when subjected  to a  strong heat.
13. CAMPHOR.
   THIS is a substance which  exists in  a great variety of
plants.   It is  found in large quantities in the laurus cam,-
phora,  which grows in China, Japan, Sumatra, &c.   And 
DISCOURSE  XI.
343
it is also  obtained from the roots of zedoary, from thyme,
rosemary, sage,  and from many other of the odorous plants
which contain essential  oil after they are allowed to dry.
Most of  the essential oils deposit camphor, when they pass
to the state  of resin, by the absorption  of oxigen.   But
the camphor of the shops  is chiefly obtained from the East
Indies, where it is extracted by distillation from the roots,
and in want of these from the other parts of the laurus cam-
phora.  These are put with water in an iron still, without
a long worm attached to it (in which state it  is called an a-
lembic.J  In  the  head of the still cords of rice straw are
arranged regularly across it, and the head is then placed on
the  still  and fire  applied.  Part of the camphor sublimes
and  attaches itself to the straw  within the head ;  while
another portion is carried into the  receiver with the water.
The camphor is then brought to Europe, and has hitherto
been purified  chiefly in  Holland, by subliming it in large
glass vessels, with one ounce  of lime.   Professor Wood-
house has written an excellent paper on the purification of
camphor in the Medical Museum, published by  the very
useful and respectable Dr. J. R. Coxe of Philadelphia.

   Camphor when purified,  is a white concrete substance
of a strong  smell and taste; very volatile, soluble in ar-
dent spirit, and resembling  in some of its  properties  the
essential oils.   It  burns  readily,  leaving  nothing behind.
The products formed are carbonic acid and water,  which
shew that it is composed of hidrogen and carbon*  When
 the nitric acid is distilled from it, an  acid is formed called
 the camphoric acid, which has a bitter as well as sour taste.

   Camphor is one of the best remedies used in the healing
 art.   It is given in doses of 5 or 10 grains 5 or 6 times
 a-day in nervous fevers with  great advantage.   Rubbed up
 with water and sugar, or mucilage, it forms a  julep much" 
344
DISCOURSE XI.
used in the  above cases.   Dissolved in ardent spirit, it is
applied to parts affected with  chronic rheumatism,  with
^reat advantage.
XIV. WAX.
  THE obvious qualities of wax are well known.   It  is
obtained from the vessels holding the honey of bees.   The
bees procure it from the flowers, leaves, and other parts of
vegetables.   When exposed to heat it melts, and if in con-
tact with oxigen it burns very readily.   With the alkalies it
forms  soap.  It is insoluble in water or ardent spirit, but
is soluble in essential and expressed oils.  It bears the same
relation to the expressed oils that camphor does to the essen-
tial.   It appears to owe its solidity to oxigen,  and has con-
sequently been considered as an oxid of expressed oil.  When
distilled an oil is obtained from it.

  The wax,  when obtained  from  the bee hives, is of  a
yellow color.   In  order to bleach, or render it white, it  is
usual to expose it to the open air and sun for some time.  A
more expeditious  method of bleaching it, is to expose  it
to the action of the oxi-muriatic acid air.

  Wax is the basis of  most of the  plasters  used by physi-
cians.  It is used also to give a gloss to good house furni-
ture. 
DISCOURSE XI.
34.5
XV. BITTER PRINCIPLE.
   MANY vegetable substances  have a very bitter taste,
 such as quassia wood, gentian, and  columbo roots ;  leaves
 of  the hop, Peruvian bark, camomile flowers,  and coffee.
 These owe their power of exciting the sense of bitterness,
 to a particular substance called the bitter principle.   No che-
 mical examination of this, has hitherto been published, nor
 are we  acquainted  with the means  of separating it from
 other bodies, or ascertaining its presence except by the taste.
 It may, however, be procured tolerably pure, by digesting
 water over  quassia wood split fine,  until it becomes of a
 yellow cast  and very brittle; this is then to be evaporated
 by a slow fire; and a substance will remain in the vessel of
 a brown color, intensely bitter, and very soluble in ardent
 spirit and water.


  It is the bitter principle of plants,  which  is supposed to
give them the power of strengthening the animal system,
or in other words, giving tone to the  body.  As it is solu-
ble  in water and ardent spirit, it is most  generally given to
increase the tone of the system, either in water,  forming an
infusion,  or in ardent  spirit, forming a tincture.   They
act as a strong artificial stimulusvto the system, and their use
should be avoided by all who are in good health,
Xx 
;Hy6
DISCOURSE XI.
XVI. NARCOTIC  PRINCIPLE.
  THIS principle has never been obtained  pure.  Its ex-
istence is only known by its powerful effects on  animals,
inducing sleep, disease and death, in small doses: hence it is
called, also, soporific or stupifying matter of plants.  It exists
in brgest quantities in fox-glove, opium, leaves of the cherry
laurel, of the deadly night shade,  of the thorn apple  (da-
tura stammonium,) of the common black henbane,  of the
 wild rosemary, of tobacco,  in  lettuce, &c.   It appears
 soluble partly in water,  and partly in ardent spirit.


   Besides  the  fifteen substances just  considered,  as  the
 proximate principles of  plants, others have been named by
 different authors, as the acrid principle, coloring matter, subery
 or  common  cork, which  is  found in  the barks of trees;
 sarcocall  or common  liquorice,  and one or two  others.—
 Perhaps some  of  them, as well as others that one would
 notice while examining  the  products  of  the  vegetable
 kingdom, may  possess properties a  little  different from
 the substances  we  have considered.    But  this  should
 riot lead persons to form  an  endless list of the proximate
 principles of plants; to avoid  which, such bodies should be
 classed among those they most resemble. 
DISCOURSE XI.               347
PUTREFACTION OF  VEGETABLES.
   THE various substances forming vegetables, finally un-
 dergo changes by which they are converted into elements,
 or  into compounds  of a  different  kind.   This is usually
 called putrefaction.  The  tendency  to it differs in different
 plants, and this tendency in the same plants varies with the
 circumstances in which it  is placed.   It  takes place gene-
 rally more speedily in the presence  of atmospheric air im-
 pregnated with moisture and warm seasons; and when the
 quantity of vegetable matter present is considerable.  The
 bulk of the mass gradually lessens, and becomes soft;  car-
 bonic acid, and other disagreeable airs are extricated; heat
 is generaly made sensible,  and the greater part of  the mass
 is carried off.   The  remainder consists chiefly of carbon,
lime,  potash, soda, or any other fixed body which may not
have been converted into air: this gradually becomes blend-
 ed  with the earth, and serves for  the growth of other
plants.


  The  substances formed during  the putrefaction of the
 plants, must at once  appear to depend on two causes;  one
is the particular substance present in the vegetable, and the
other  is the particular state ox circumstances created for their
affinities to be exercised.  Hence carbonated hidrogen, car-
 bonic acid, nitrogen, amrrtoniacal, and many other airs, are
 occasionally thrown off from vegetable putrefying matter. 
J4S
DISCOURSE XI.
  Before dismissing this subject, it may be of use to sub-
join the following statement, which contains a general view
of the most striking properties of  the proximate principles
constituting vegetable substances*

   1.  Wood or ligneous fibre.  Tasteless,  insoluble;  resists
putrefaction; leaves much  charcoal  when heated in  a
close  vessel.

   2.  Acids. Possessed of all the general properties of acids;
easily decomposed by heat.   Six different kinds,  the citric^
malic, oxalic, gallic, benzoic, tartarfeous and acetic.

   3. Tannin. Soluble in water and ardent spirit; precipi-
tated by gelatine, or animal jelly.  Taste astringent;  unites
to the jelly of hides, forming leather.

   4. Oils. Two kinds : volatile or essential, obtained chie f-
 ly by distillation : expressed or fixed, obtained by pressure
 on seed.   Of each kind, several varieties,  named according
 to the name of the plant from which it is obtained.   All of
 them unite to the alkalies, forming soap.   They are com-
 bustible.

   5. Gluten. Soluble when extracted from the plants.  Co-
 agulated by the heat of boiling water.   Readily putrefies,
 emitting ammonia.

   6. Fecula or  starch.   Insoluble in  spirit or cold water.
 Forms a  paste with hot water.  Taste insipid.   Exists in
 many of the nutritive seeds and roots of plants.   When in
 a state of combination, as in wheat, undergoes the panary
fermentation, by which it may be made into loaf bread. 
DISCOURSE XI.
349
   7. Indigo.   Obtained by fermentation ; color blue.  In-
soluble in alcohol and water.   Soluble in sulphuric ncid,
forming the liquid blue, much used in dyeing.

   8* Sugar.  Taste sweet.  Soluble in  water and alcohol.
Obtained  from many plants.  Is susceptible of undergoing
a  change when  combined with more than one fourth its
we;ght  of water, by  which  it is converted into vinous li-
quids,  which  on distillation yield alcohol or ardent spirit;
which unites to the acids, forming ether.

   9.  Gum. Soluble in water,  in which state it is called, mu-
cilage.   Insoluble in alcohol.  Taste  insipid.   Very nutri-
tious, and abounds in many plants.

   10.  Resin.  Insoluble in water;  soluble in alcohol, ether
and oils,  in which state it forms a varnish.  With  the oils
from trees they constitute turpentines and balsams.

   11.  Extract.  Soluble in water and alcohol; insoluble in
ether ;  unites to oxigen when heated, by which  it loses its
power to act on animals.

   12.  Elastic gum. Very elastic; insoluble in water and al-
cohol; soluble in ether.

   13. Camphor.  Strong odour ;  may be sublimed by heat ;
insoluble in  water.   Soluble  in alcohol and  oils.  May be
converted to an acid :  burns with a clear flame.

   14. Wax. Insoluble in water.  Soluble in alcohol, ether
 and oils.  Burns very readily, and is very fusible.

   15.  Bitter principle. Soluble in water and alcohol; Very
 bitter ;  acts as a tonic on animals when swallowed. 
350
DISCOURSE  XL
   16. Narcotic principle.   Sparingly soluble  in hot watar
and  alcohol.    In large  quantities is  a deadly poison to
animals.

   All of which substances, either alone or in combination,
as they exist in plants,  finally undergo a putrefaction or de-
composition, by which they  are either converted to the ele-
mentary state  or into other compounds less complicated. 
DISCOURSE XII.
  WE have seen the different substances, which are con-
tained in plants.   We have now to examine the manner in
which these substances are produced,  and the  circumstan-
ces  favoring their production.   We have stated that they
were chiefly composed of  carbon, hidrogen, oxigen, and ni-
trogen, with but small portions of heat, light, and occasion-
ally of five or six other elementary bodies.   It must readily
appear that those elements are not applied for the growth of
plants in  a pure state.   To determine in what states of
combination they are afforded for  the formation of vege-
table bodies, must be an  object of  considerable importance
to the agriculturist.

  Natural historians have long since observed, that  all
plants arise from seeds, situated in  the soil or earth, under
particular circumstances.  When  situated in die earth, 
352
DISCOURSE  XII.
where their elements exist they vegetate; their structure, and
their  qualities  become  materially altered;  each particular
seed assumes the particular form for which it was intended,
or rather which seems stamped on it by nature.  The roots,
extend considerably, they absorb the food for the  plint,
which is conveyed in vessels to the various parts, where it
acquires the necessary properties.   In the  first state, into
which it is changed, it is commonly called sap.   This sap
is afterwards changed into innumerable different states,  to
suit the purposes of  the respective parts of each plant.

  The food being applied to the roots of plants, we must
inquire  by what means it unites to the seeds,  and then cir-
culates through them in the state of  sap.

   To explain  this,  philosophers have been at great pains,
and have offered a variety of conjectures more calculated to
shew their ingenuity than to account for  the phenomena.
They have, however, at length  made satisfactory explana-
tions.   Having ascertained that the seeds and roots of plants
were porous, and that  porous  bodies  absorbed moisture ;
and having clearly shewn that vegetable bodies contain ves-
sels,  which possess  the  power of contracting and dilating,
or in  another word irritability.  It now appears very obvious
and certain that the roots,  by  virtue of their orifices or
pores, attract the fluid  substances around them, and con-
vey them to the vessels   possessed of a contracting  power,
at  which time these small vessels contract  and propel the
juices or circulate the sap through them.   This simple ex-
planation has not been very long made.  The whole circu-
lation of the juices  was attributed to this porous, or,  as it is
called by philosophers,  capillary attraction.  The discovery
that vegetables possess  irritability, led  to the rejection  of
this supposition.  That  it is in  consequence of this irrita-
bility of  the vessels that the fluids are circulated in them has 
DISCOURSE  XII.
353
been rendered unquestionable,  by Professor Barton of Phi-
ladelphia, who has much raised abroad the character of his
country, as the seat of science.  This  celebrated naturalist
found,  that plants growing in water vegetated with much
greater  vigor, provided a little of that  powerful stimulus,
camphor, was thrown in the  water.    From some experi-
ments which I  have instituted, I am led to  believe that a
little ardent spirit will produce the  same effect.

  The next and not less important inquiry, which presents
itself for our consideration,  is the means by which the food
of plants is assimilated, or changed  into a substance of the
same nature as  that of the plant;  or, in other words, the
means by which the matter entering the plants is converted
into sap, and this sap into the  various compounds found  in
plants.

  To account for these important changes wrought in the
vessels of plants,  philosophers have advanced but two the-
ories which have a claim for the least attention.  The first
which prevailed was :  that the  various substances found in
vegetables,  previously existed in a formed state in the food,
that the vessels of the plants served merely to filter, strain,
or  separate these fluids, and  that when the sap  passed
through any part, it left  that particular substance behind
which  was necessary for the part, and which could not
pass through the strainer or vessels.  This  is called the me-
chanical theory of secretion.   It surprises  us  in  nothing
more than that it should have ever  been seriously believed
by  any  one.  For it realy seems difficult to have credulity
enough to  believe that so  many thousands of substances
could exist  in the sap of plants without one's being able to
 detect the  presence  of any of  them.
Yy 
354
DISCOURSE XII.
  The next theory advanced to explain the mystery  was :
that  in consequence of the  irritability  of the vessel  of
plants, these vessels when the sap was conveyed to  them
contracted and  dilated, or in other  words so  acted as not
only to cause the sap to pass through them, but to change
its state from that of sap to sugar, gum,  resin, wood, &c.
And thus it is stated, that by a peculiar action of the vessels
on the sap of  plants, are all the changes wrought which
we notice in the vegetable kingdom.

  This theory  early struck me as being incorrect.   How
the simple action of tubes could cause not only the circula-
tion of a fluid through them,  but  its conversion into  innu-
merable states I really could not conceive.  It appeared to
me,  that the true theory,  characterized by simplicity, re-
mained to be revealed.

  In the course of  my pursuits I frequently  noticed, that
the affinities or laws of the same compound, were changed
by change of circumstances.  Throughout these discourses
I have endeavored to impress the same on others. Indeed,
no one can doubt it who  has mind enough to form  a dis-
tinct idea.  No one will say, that the particles constituting
bread, exercise the same affinities in a heated oven,  when
they are  converted into charcoal, as they do  when left  at
a common temperature.   We must attribute  the difference
in all such cases, to a difference in the affinities of the mat-
ter  exercised ;  and we must attribute this different exer-
cise of affinities to a difference in the circumstance,  state,
or, condition in  which the bodies are placed. This we must
do, although we cannot say on what the particular state de-
pends.  And although we know not, in what one state dif-
fered! from another. 
DISCOURSE  XII.
3-55
  In the course of  this work I have stated, and it will be
believed  by  all who examine, that not only heat, light,
electricity and  galvanism, create states in which the affini-
ties of the particles of matter are variously exercised,  but
that other bodies have sometimes great influence in creating
states for the exercise of the affinities of  matter of a  dif-
ferent kind.  Hence you may put two compounds together
of a particular  kind, and no action will ensue unless water
be added, which, when done, new affinities are exercised,
and the water  remains unchanged.   A number of  similar
facts might be mentioned.  The observation before made
may be  here repeated, namely,  that although we  cannot
say in what, a state for  the exercise  of the  affinities of
matter consists, yet  it no doubt depends  on a mechanism,
or mechanical arrangement of matter which cannot be de-
scribed.   A variation in the mechanism of a body, would
naturally lead us to suspect that there would be a variation
in those  affinities of a compound which were exercised in
the first state.

  Aware of  these considerations, or principles, the changes
occurring in vegetable juices can  no longer be mysterious.
Throughout every part of every plant there  are pores, or
vessels: and in almost every  part, there is a difference in
the mechanism or arrangement of these vessels.   Inasmuch
therefore, as we find a difference in this mechanism, should
we be led to expect  a difference  in  the affinities  of the
matter exercised.  Accordingly we find that the compounds
existing in the  different parts of plants, do  vary as much
as their mechanism or organization.

  The theory then to explain the  formation of vegetable
substances, seems very simple.  A seed is placed in a soil;
it attracts substances from the earth;  these substances con-
stituting its food enter the pores or vessels of the seed; in 
356
DISCOURSE XII.
these pores, or in  this state their affinities are exercised, in
consequence  of which  they are converted  into sap; the
different parts of the plant have a different mechanism, in
consequence of  which this sap  assumes in one part, pro-
perties different from those in another;  in one  part, its af-
finities  are exercised" whereby it is  converted  into fibrous
vessels possessed of irritability or a contractile power;  in
another it is converted into  mucilage; in another into sugar;
in another into resin; in another into an acid; and so on
of every juice found in plants.  And thus a particle  of
matter may have its  affinities exercised, and then itself  be
an  agent creating states  in  which the same affinities of
other matter ar>e exercised.

   It should not from this be supposed, that all the  parts of
a plant are composed of the same elements; although they
are all formed from the sap, and  on the same principles, viz.
by the exercise of affinities regulated by a  mechanism,  or
state created by some intervening body.  This would be in-
correct, as we find on analyzing some parts, their elements
differ in proportions very considerably.   If we can conceive
of the  different exercise  of  the  affinities  of  particles  of
matter in different states,  we can conceive  that when the
sap  passes through certain vessels,  most  of one or two of
its elements  may  go unchanged,  while its other elements
are altered: for example, we can conceive of the hidrogen
and carbon of the sap uniting in one part to form oil; and
the remaining constituents of the sap passing unchanged for
other purposes; in another part, the oxigen is  retained in a
small quantity,  so as to form a sugar with the hidrogen and
carbon* in another part the oxigen  is retained in such quanti-
ties as  to form an acid;  and so of all the rest  of vegetable
substances. 
DISCOURSE  XII.
357
  No doubt, light has considerable influence in creating
states for the exercise of the affinities of the sap in the up-
per parts of the plant.  In the ripening of fruit, its influ-
ence  is remarked by every one.   This ripening of fruit,
by which acid and acrid juices are converted into such as
are sweet and  mild, tends very much to establish the ex-
planation of vegetation, which  I  have ventured to offer.
The conversion of sour fruit when baked into a  sweet mass
has the  same  tendency.  In  each  of these  cases,  the
charges must unquestionably arise from the different exer-
cise of chemical laws in different states.   Surely in an ap-
ple, a water mellon  or a strawberry,  there are no little
vessels which can make sugar by a peculiar action.

  Having given the  above explanation of vegetable growth
and secretion (which from the obscurity of the subject will
I fear appear obscure  to  some) I shall make  mention of
some of the most remarkable functions of the  upper parts
of  plants, and will then proceed to the consideration of the
soils most favoring vegetation.

  It  is known  that after the  seeds  of  plants  sprout,
that a part rises out of the earth, on which is formed seed
for the future propagation of the same plant.  On this part
we almost universally meet with leaves.   These leaves are
found to act as important a part towards the upper  part of
the plant,  as the  roots do to the lower part.   Hence the
plants soon decay if  deprived of the one or of the other.
Nor is this surprising,  for a  number of experiments have
very decidedly  shewn,  that they are instrumental not only
in preparing nourishment but in receiving  it from the at-
mosphere for the support of  the whole.  They are to the
plants what the lungs are to animals. 
358
DISCOURSE XII.
   The sap is no sooner conveyed to the leaves by the con-
traction of the vessels,  than a considerable part is transpired,
or thrown off by evaporation. The quantity thus transpired,
bears a very  great proportion  to the moisture  imbibed.
Mr. Woodward found that a sprig of mint in 77 days, ab-
sorbed 2558 grains of water, and  yet its weight was only
increased  15 grains. Another branch absorbed  14190 grains,
and had its weight only increased 128 grains.  Dr. Hales
found that a cabbage transpired daily a quantityof water equal
to half its  weight, and that a sun flower three feet high trans-
pired in a day  lib. 14oz.  He shewed  that the quantity
of  perspiration in  the  same plant was proportionate to the
surface of the leaves, and that when the leaves were taken
off,  the transpiration ceased.  He found too that the trans-
piration was nearly confined to the day, that very little took
place at night, or in cold and wet  weather,  and that the
sun much promoted it.  On collecting and examining the
matter transpired,  he found it to be  nothing more than wa-
ter with a little of  the odour of the plant.

  The leaves  appear to  have particular organs adapted for
throwing  off part of the sap by transpiration,  and these ap-
pear to be on the upper surfaces of the leaves, as the trans-
piration is almost entirely stopt when the upper surfaces are
varnished  over.  Gradually the leaves become unfit for this
process, and then they drop off in the fall of the year.

  The first great  change then Which takes place upon the
sap after it  arrives at  die  leaves, is  the evaporation of  a
great part of  it, and consequently what remains of it must
be changed in its proportions.

  Further changes are also wrought.  Pr. Priestly  made
the important  discovery, that the leaves had the power of
decomposing  carbonic acid, of uniting to its carbon  and of 
                   DISCOURSE XII.               359
leaving the oxigen in a state of purity.   When this oxigen
or vital air was first observed to escape from plants,  it was
supposed that plants had  the capacity to give out vital air,
which supplied  the place of  that  consumed by  animals.
But this  was a mistake, and has been proved to be  so, by
the indefatigable chemist, Dr. Woodhouse of Philadelphia.
He found that plants immersed  in pure  water,  which had
been  distilled, did not give out oxigen ; but when pump
water  was used, or any  water which  contained  carbonic
acid,  then oxigen  air was formed  in consequence  of the
plants depriving the air of its  carbon.   Moreover,  it has
been shown that plants do not vegetate unless carbonic acid
be present.   If  they be put in air deprived of all this acid,
they vegetate for  a short while, in consequence  of their
parting with  a  little of their carbon to unite to  the  sur-
rounding oxigen  to form the  carbonic acid, which then
serves to nourish them.   But  if quicklime be around them,
which absorbs  the acid as fast  as  it forms, they  do not
vegetate.

  Plants in all probability acquire most of their carbon by
decomposing  carbonic  acid.  This decomposition  chiefly
goes on during the day, when the action of the sun has
great influence.   The green color of the leaves depend en-
tirely on their  vegetating in the light.    For as  observed
while  considering  light, this color  will  be  entirely  lost in
all  plants, if they be  included  in boxes, or in  any thing
which will prevent the contact of light.

  The sap besides losing water when brought to  the leaves,
uniting to carbon, and being acted on by the light, undergoes
other changes.   During the night they absorb oxigen as has
been  stated very evident by Dr. Ingenhousz ; who also as-
certained that they grew very well in oxigen air,  and  that
they emitted carbonic  acid which  afterwards  served  for 
SCO
DISCOURSE XII.
nourishment.  They also absorb  moisture from the atmos-
phere.   The  great effects which  dew, slight showers of
rain,  and even wetting the leaves of plants, have in increas-
ing the vigor  of plants, has been long observed.   That
they  imbibe moisture,  was made nearly certain  by Dr.
Hales, who found that the plants increase considerably in
weight when  the  atmosphere is moist.   Mr. Bonnet put
this beyond all doubt, by discovering that the leaves conti-
nue to live for weeks when one of  their surfaces  is applied
to water ; and that they not only vegetate themselves, but
imbibe enough water to support the  vegetation of a whole
branch, and the leaves belonging to  it.   The absorption
chiefly takes-place at the under side opposite to that on which
the transpiration goes on.

   It must  appear, that the perspiration,  the  absorption of
carbon, oxigen and moisture, and the action of  light pro-
duces  very important  changes on vegetables.  We  will
now consider  the  nourishment received  by other parts of
the plant, namely  the roots.

  It has  long been known that the roots of plants perform
most  important  offices,  and indeed  it was  supposed for-
merly that it  was only by  the roots, that  nourishment
was  received.   This nourishment  must  be  the elements
before named, which are found in vegetables when decom-
posed.  But these elements are not  afforded  in the simple
or uncombined state.   We shall examine the state in which
the food is absorbed.

  In the first place, it is certain that plants will not vege-
tate without water, for whenever  they are deprived of it
they wither and die.   Hence the well known use of  rains
and dews.   Water then is at least an essential part of the
food of plants.   Many plants grow in pure water, and in 
DISCOURSE XII.
361
Consequence of this Van Helmont,  Boyle and others have
maintained  that  it was the sole food of  plants.   But this
requires no further refutation than the fact, that elementary
substances are found in plants which are not found in water.
Moreover, in general it is only a certain proportion of water
which is  serviceable to plants,  and too much of it proves
as destructive as too little.   The greater  part  of them are
entirely destroyed when immersed in that fluid  beyond a
certain time.   Hence,  different soils are necessary for the
proper growth of different  plants.  Rice, for  instance, re-
quires a  very wet soil: when  it is sown on  the  ground
where wheat grows luxuriantly, it will not grow ;  and, on
the contrary, wheat will rot instead of vegetating in rice
fields.

   Almost all plants grow in  the earth,  and almost every
soil contains at least three or four of the elementary earths,
called alumine,  silex,  lime,  and magnesia.  The chief use
of these earths is to  administer, as it were, the  proper
quantity of food to the  plants; at least, they afford a kind of
bed in which the roots  attract those substances they require.
Moreover, they serve to collect food:  for, it is an unques-
tionable fact, that soils absorb,  at least when opened,  con-
siderable  quantities of  airs from the atmosphere.   They
generally  absorb ©xigen air and carbonic acid, each of
which proves useful to vegetables.  Hence the  advantage
of deeply ploughing land,  and leaving it at rest foj this ab-
sorption to take place.   The earths are  also useful in other
respects.  But few plants are met with which do not  con-
tain more or less of  them ; and it is reasonable to  suppose
that at least they form a small part of the food of the plant.

   Besides water and the earths, carbon is necessary for the
growth  of plants.   It forms a most important  part of
                          Z z 
362
DISCOURSE  XII.
nearly every vegetable.   From a  great  variety of experi*
m,ents, it has been ascertained that the quantity of carbon
in fertile soils is very great.   Generally it is to this that they
owe their dark color.   Fourcroy  and others, by various
examinations have found, that at least one sixteenth of good
soils consists of carbon.  It does  not,  however, exist  in
a state  of purity.   Large quantities  are  combined with
oxigen,  in  the  form  of  carbonic  acid,  which is also
united to some other substance.  The fertility of  soils
may  generally be  judged  of by the quantity  of carbon
they  contain.   To  judge  of  this  quantity,  the  soil
should be  inclosed in a retort, to which a  little nitre is
added, and exposed to a strong heat.  The air which  comes
over should be preserved by  means of the pneumatic appa-
ratus ;  and the quantity of  carbonic  acid will give an idea
of  the quantity of carbon.   It is scarcely necessary to  ob-
serve, that in this experiment the oxigen of the nitre unites
to  the carbon and  forms fixed  air.   Perhaps, nitric  acid
 would answer better than nitre.   The carbon, however, is
 of no use if it exist in that  solid state, as in diamond and
 pit coal, in  which the power  of the vegetables is not suf-
 ficient to destroy its cohesion.

    Many plants also require a portion  of nitrogen.   The
 state in which they unite  to  it is not known.    Perhaps,
 they take it from the water ; perhaps, they take it from the
 remains of dead  animals; or, perhaps, they take it from
 nitre.   All  these substances must exist in proper propor-
 tions,  otherwise the plants will not  thrive.  An excess or
 deficiency of either is injurious.

    But without heat plants will not vegetate in any mixture.
 Below the freezing point  none of  them increase in bulk.
 Every  plant seems to require a degree of  heat  pecu- 
DISCOURSE XII.
363
liar  to  itself, at which it  commences and continues to
grow.   Hence,  each seed has a particular season at which
it begins to germinate, and this season varies with the tem-
perature of the air.  Hence, the same seed sown at the
same time in different countries vegetate differently.

  Such being then the food  of plants, and such  the cir-
cumstances in which it is taken, we will proceed to consi-
der the  art of improving soils, by which is meant,  render-
ing them more capable of supporting vegetation.

   In the first place, it must appear very evident that great
attention should be paid to the nature of the plant  to be
cultivated.   Should it be one of the kind requiring  much
water ;  and should the country not be subject to frequent
showers, then a soil calculated for  the retention  of mois-
ture is to be chosen.  Such soils are those of the clay kind.
They contain great quantities of alumine; and while con-
 sidering this  elementary earth, it was observed that it was
 remarkable for the quantity of water it was capable  of re-
 taining.  These are called wet soils.  The soils containing
 much sand, or silicious earths,  are of an  opposite nature,
 and are consequently called dry soils.  The soils containing
 lime and magnesia,  are intermediate between these ex-
 tremes;  they render a sandy soil more retentive of moisture,
 and diminish the wetness of a clayey one.  By bringing,
 therefore,  together the proper proportions of these earths,
 we may form a soil of any degree of dryness or moisture we
 please   While, however, we are considering this, we must
 not lose sight of the power or strength of the roots, by which
 they are enabled to penetrate and spread about  in the earth.
 This power, in some instances, is so inconsiderable, that the
  roots  are  confined to a very small space.  In such cases,
  some light substance  is necessary, which so diminishes the
  solidity of the clay, that the roots  can grow  in any diree- 
364
DISCOURSE XII.
tion.   But the selection of a soil must, after all, be much
regulated by the quantity of rain which usually falls in the
place.   If but little rain falls, the soil, however retentive  of
moisture, must remain dry ; and if rain falls very frequent-
ly,  the soil must be  very open  if  it be not constantly wet.
In a rainy country the soil ought to be open, or contain a
large proportion of sand; and in dry situations, there ought
to be  great quantities of clay, which is retentive of mois-
ture.  Lands on a plain should also, under the same circum-
stances,   be  more  open, or contain more sand than those
on hills.

   But the chief means by which soils are generally improv-
 ed, depend on the  addition or mixture of certain articles,
 called manures.

   Concerning the  kinds and the  nature of manures, philo-
 sophers and farmers have long differed.   The first have dis-
 puted much,  and the practices of the second have not  less
 clashed.  These differences, however,  are now fast subsid-
 ing ;  and a few simple truths have been established, by which
 all apparent contradictions may be explained ;  and the art of
 improving land  may rapidly progress.

    The  art of improving land, so as to promote vegetation,
 may be considered  as depending on these causes.  The first,
 is the application of such substances as stimulate the vessels
 of the plant (or increase their action) so that they unite to
 parts of the soil with greater rapidity.   The second is the ap-
 plication of such substances to the earth, as convert the bo-
 dies in the earth, into that state in which they favor vegeta-
 tion : Such might  be called solvents.   And the third, is the
 application  of  such bodies to the earth, as enter into the
 composition of  the growing plants. 
                  DISCOURSE XII.               365
  Of  the  substances  which operate in the  first  way:
namely, by increasing the action of the parts of the plant,
there are but few known.  Heat, light, and electricity are
almost the only kind.  From Professor Barton's experi-
ments, camphor appears  to  operate  in  a  similar way.—
Diluted ardent  spirit will have,  I believe, a similar effect.
But  perhaps, it will never be an object to applv such sub-
stances to vegetables;  excepting heat, which is sometimes
applied, particularly by  means  of the hot-beds, formed by
putrefying manures.


  Of the substances acting in the second wayt  namely, by
decomposing bodies in the earth, so as to adapt them for
becoming food to the plants, there are also but few.  They
operate in such a manner, a6 to excite a  kind of putrefac-
tion  in the  compounds  containing  the  elements of  the
growing vegetables.   For example, a ' soil may contain
roots,  which not having putrefied, do not aid vegetation.
Now all substances which will  cause or hasten the putre-
faction of such bodies, are  to be ranked under this head.
The substances acting in this way,  are a small quantity of
common salt,  and  a small quantity of  the  plaster  of
Paris,  each  of which  in   small  proportions are found
to expedite putrefaction  very much.  In  some  instances
they no doubt operate  as manures, differently.  Besides
these,   it is universally known that heat,  moisture, and
air,   have  great  influence  in  hastening  putrefaction.
But the value of these is somewhat lessened, as they carry
off  a  part of  the matter after it has putrefied.  However
such kinds of substances must be of unquestionable value,
as the bodies contained in the  earth might as  well not be
 there, if they be not in a state in which they are capable of
 uniting to  the vegetables;  and thereby promoting  their
 growth. 
$66
DISCOURSE XII.
   But the most important manures operate in the third way :
namely, by imparting to the soil, the particular kind of mat-
ter best suited for entering into the compos'tion of growing
vegetables.  Of this kind the most remarkable are pit  and
charcoal, reduced to a fine powder;  the manure of animals,
as well as their putrid  bodies and pounded  bones ;  ashes;
putrid vegetables, particularly those of the saline kind, such
as tobacco, weeds,  &c.  lime, plaster of Paris, chalk, the
strong diluted acids, and, in fine, all substances containing
either hidrogen, oxigen, carbon, or  nitrogen,  in such a loose
state that the plant can attract and  unite to them.

   To the reflecting world it has long been a subject of asto-
nishment, that small quantities  of these various manures,
frequently tend, in a great degree,  to favor vegetation; so
that,  in some  instances,  one hundred pounds of a manure,
will produce an increase of vegetation in one year, equal to
10,000 weight.  But on examining the subject, we find less
cause for wonder.

   We know that for the growth of a plant, certain propor-
tions  of  certain  elements,  are  indispensably necessary.
Without any one of these constituents, the rest cannot per-
form  their part.  Suppose that for the formation of a cab-
bage it was necessary  that there should  be  five pounds of
water, two of carbon, and one ounce of nitrogen.  The wa-
ter and the carbon could be  of no service, unless the nitro-
gen were present.   Now on adding a little nitrogen,  the
plant  instantly united with it, and in consequence exercised
its power to combine with large portions of  water and car-
bon, so as to increase to a great bulk.   In this manner ma-
nures act.  They yield  to  the  vegetable that something
which the soil does not contain in abundance, and in conse-
quence of this the vegetable is enabled to combine with
large  quantities  of its other constituent parts, which exist 
DISCOURSE  XII.
367
either in the earth or in the surrounding atmosphere.  They
resemble animals in this respect.   It is well known that all
the food a man can swallow  is of no service to him unless
he can also have a few grains of vital air in his lungs.

   It may not be amiss to  make some remarks concerning a
few manures which claim particular attention, and first of

                      PIT COAL.
  WHEN considering this article in another place, I stated
that in a given bulk it contained a great quantity of carbon •,
a substance which enters  into the composition of almost
every vegetable, and which forms more than half the body
of half the products of the vegetable kingdom.  Now as car-
bon must enter into the composition of the domestic plants,
it must be of  service in improving soils.  But it has been
stated that before carbon can enter into plants, it must be in
a certain state, in which, according to some, it may be dis-
solved in water, to be applied to the roots of plants.  Hence
they have inferred, that as pit cOal is not  soluble in watef,
so  it  cannot be of  service to the roots of vegetables; and
this has been supported by a few experiments made by dif-
 ferent persons with the coal, by which it appeared to be of
 little or no use.   Being forcibly struck with the quantity of
 carbon in this coal, I thought it very surprising that it was
 not found to be a manure.   This led me to institute several
 experiments, relative to the subject, an account of which
 was  published in most  of the public prints some months
  since.   The  result of these experiments prove that coal  is
  one  of the most valuable manures, ever applied to land.
  While  conducting these experiments I was conscious that
  the cohesion of coal was  too strong to be overcome by the 
368
DISCOURSE XII.
powers of the plant.  This led me to provide against this*
by reducing the coal to a most impalpable powder, previous
to mixing it with the earth.  When this was done, the coal
accelerated die vegetation of wheat and corn with astonish-
ing facility.   However, from my experiments, I am unable
to say what quantity is necessary for an acre of land.   But
these experiments made it unquestionably appear

  111. That those who experimented with coal, did not  re-
duce it to a very fine powder.

  2d. That coal in the state of a coarse powder is no bet-
ter than common sand, as vegetables have not the power to
decompose it.

  3d. That coal reduced to a powder as fine as wheat flour,
will unite to plants and act as a most excellent manure  for
all plants requiring carbon for their growth.

  4th. That  great good would be  derived if mills  were
erected for reducing coal to the state of a fine dust,  as  the
coal could  be had very  cheap, from the  immense mines
found throughout the country, and the lands enriched at no
great expense.
CHARCOAL.
  AN eminent agriculturist, Mr. Young of England, ap-
pears to have been the first who found that common char-
coal was a good manure.   For it, however, to operate as a
manure, it must  be reduced to the state of a fine dust. 
DISCOURSE XII.
369
Like pit  coal, in the compact state, it is of no use.  Since
it is an excellent manure, it must appear very erroneous to
have it wasted by  fire, in many poor countries, unnecessa-
rily.  To avoid this, it would be of consequence to frve
wood converted in the new grounds into coal; then it might
at leisure be made into dust, and sprinkled on poor lands.
Now as peach trees grow well in poor  lands, and  as they
contain much carbon, would it not be advantageous to have
them planted in vacant ground, and then  after they ceased
to yield fruit, have them reduced to the state of charcoal
and sprinkled on the  earth, to prepare it for other uses.
LIME.
  THIS has, under many circumstances, been found an ex-
cellent manure.  It no doubt acts in three ways.   In one it
serves to absorb water and yield it for plants; in another to
unite itself to them; and in a third to absorb carbonic acid
from the air, and from the compound

                       CHALK;

                           OR

              CARBONATE OF LIME,
  THIS has  long been found to be a manure.   In all pro-
bability it acts by parting with its carbon  of its acid to the
plant;  or its oxigen.   Burnt bones act in the same way.

                         3  A 
370
DISCOURSE XII.
    PLASTER OF PARIS;

               OR

SULPHATE  OF LIME.
  IT has not been long since this compound was used as a
manure.   When reduced to a powder, three or four bushels
of it to the acre, appear to increase remarkably the fertility
of some soils.  In the first instance, it no doubt acts by has-
tening the putrefaction of the dead  vegetable matter.   In
the second instance, it probably is useful, by imparting to
the plants oxigen, which is contained in considerable quan-
tities in the sulphuric acid, which is one of its constituents.
On the same  principle it has been found  that a small quan-
tity of sulphuric acid is of remarkable utility to plants; also
saltpetre, and indeed all the substances containing oxigen
or carbon.  Hence  water,  impregnated  with oxi-muriatic
acid, is found to quicken vegetation, as well as when mixed
with carbonic acid.   Hence the water passing  through
dung heaps,  which is impregnated with coal and all the sa-
line  parts of  the mass, is  found to act as a powerful ma-
nure.  Hence sawdust, roots of plants, chips, sticks, straw,
&c.  on  ground are of no manner of service, until their co-
hesion is so completely destroyed, by putrefaction,  that the
powers of the living plants are sufficient to attract and com-
bine with them.

  However, in the application of manures, the agriculturist
should always have in view the making a due proportion  of
the constituents of his soil.  Too much of any  substance
will  proVe  injurious ; particularly too much of saline sub-
stances, as  salt, nitre, &c.  On calculating the advantages 
DISCOURSE Xfl.
371
derived from manure, he should also be aware, that much of
the future growth of plants depends on their early progress \
that considerable parts of the body of plants are derived
from the air, consequently that manures are the more valu-
able, as they enable vegetables to grow ;  to attract substan-
ces, water  and carbon particularly, from the atmosphere ;
which,  when the plants decay, are mingled with the soil,
whereby it becomes much improved. 
DISCOURSE  XIII.
   THE next important, and indeed the only remaining bo-
dies which  present themselves for  our consideration, are
those formed in the animal  kingdom.  Decomposition by
means of heat,  will shew that these substances are com-
posed chiefly of nitrogen,  hidrogen, oxigen, carbon, phos-
phorus and  lime,  with small  portions of iron,  potash,
soda, sulphur, latent heat and light, and in some instances
one  or two  other elementary bodies.  But such a kind of
decomposition being of no  use, we will  not take it into
consideration, and will proceed to treat, first, of a few re-
markable substances, found  in considerable quantities in
animals, which may be termed their proximate principles.
They are known by the following names:

     1. Gelatine, or animal jelly.
     2- Albumen,  or a substance like the white of eggs.
     3. Fibrina.
     4. Oils, or fat. 
DISCOURSE  XIII.               373
GELATINE.
  THIS is a substance which exists in many parts of ani-
mals.  It may be procured by the following means :

  Take a piece  of the fresh skin of an animal, such as an
ox;  separate the hair from it, and wash it in cold water
until the liquid ceases to be colored.  If the skin thus puri-
fied,  be put into a quantity of pure water, and boiled  for
some time, part of it will be dissolved.   Let the decoction
be slowly evaporated till  it is reduced to a small quantity,
and  then put it  aside to cool.   When cold, it will be found
to have assumed a solid form, and to resemble precisely the
substance known to all under the name of jelly.   This is the
substance called  in chemistry gelatine.  If the evaporation be
still  farther continued,  by exposing the jelly to dry air, it
becomes hard,  somewhat transparent, breaks with a glassy
fracture, and is, in short, the substance so much employed
in different arts,  under the name of glue.   Gelatine,  then,
is precisely the same substance as glue ;  only we must sup-
pose it free from those impurities with  which glue is al-
ways mixed.

  Gelatine is nearly colorless when  pure.  Its consistence
and hardness vary  considerably.  The best  kinds are  ve-
ry hard, brittle, and break with a glassy fracture.  Its taste
is insipid, and it has no smell.   When thrown into water it
swells, but  does not dissolve ; when  taken out it is soft;
and on drying recovers its appearance.   If in this state it be
put  into  warm water, it very soon dissolves and forms a
solution.  In this state it very soon putrefies; an acid makes 
374
DISCOURSE XIII.
its appearance; a fetid odour is exhaled, and afterwards aim
monia is found.

  The  acids dissolve gelatine, but the changes they  pro-
duce on it are not known.   It is insoluble in ardent spirit.
It is most remarkable for its combining with the vegetable
substance tannin, and forming with  it an insoluble  com-
pound,  of which mention was made while considering the
tanning of leather.   When a solution of tannin is added to
gelatine, a copious precipitate soon appears, of a  white
color, and somewhat resembling  vegetable gluten.   This
compound dries in the open air, and forms a brittle, resinous
like substance, not susceptible of putrefaction, and resem-
bles over tanned leather.  The precipitate is, however, solur
ble in a solution of gelatine.

   Gelatine, like all other constituents of animal bodies, is
susceptible  of numerous shades of variation in its proper-
ties,  and of  course  is divisible into a number of species.
Several of these have been long known and  manufactured
for different purposes, among which are the following.
COMMON GLUE.
  THIS has been  long manufactured  in  many countries,
and employed to connect pieces of wood together.   It  is
extracted by  water from animal substances, and differs in
its qualities according to the substances employed.  Bones,
muscles, tendons,  ligaments,  membranes  and  skins  all
yield  it; but  that  of the  best  quality is obtained  from
skins, and  those too of the oldest animals.   The paring* 
DISCOURSE  XIII.              375
of hides, pelts,  the hoofs  and  ears  of horses,  cows,
sheep, &c.  are  the  substances  from which it is usually
extracted.  They are first digested in lime water to clean
them,  then steeped in clean water, laid in a heap till the
water  runs  off, and then boiled in large metallic vessels
with pure water.  The impurities are skimmed off as they
rise;  and when the whole is  dissolved, a little alum or
finely powdered lime is thrown in.   The skimming having
been continued for some time, the whole is strained through
baskets and  allowed  to  settle.  The clear liquor is gently
poured back  into the kettle, boiled a second  time,  and
skimmed until reduced  to the  proper consistence.  It is
then poured info large frames,  where, on cooling, it  con-
cretes into a jelly.   It is in this state  cut by a  spade  into
square cakes, which are  again  cut with wire into  thin
slices and exposed to the air  to dry.   The best glue  is ex-
tremely hard and brittle, has a dark brown color, and no
black spots: when it is soluble  in cold water  it is a proof
that it wants strength.

   It  may not  be unnecessary to remark  that the  skins
which dissolve most readily in boiling water afford the most
glue ;  so that the most supple hides yield  the weakest glue,
which is very soon obtained from them by hot water.   The
skin of the eel  is very flexible,  and affords very readily  a
great proportion of gelatine or glue. The skin of the shark
also yields it readily and in abundance :  and the same is ob-
served of the skins of hares,  rabbits,  calves, and oxen.
The difficulty of obtaining  the glue,  and its goodness al-
ways increases with the toughness of the hides.  The  hide
of the rhinoceros, which is exceedingly strong and tough,
 far  surpasses  the rest in the difficulty of solution, and in
the  goodness of the glue.   When  skins are boiled   they
gradually swell  and  assume  the appearance of hornr  then
they dissolve slowly. 
376
DISCOURSE  XIII
SIZE.
  THIS substance differs from glue  in being colorless and
more transparent.   It is manufactured in the same way, but
with more  care.  Eel skins, vellum parchment, some kinds
of white leather, and the skins of horses, cats and rabbits,
are the substances from which it is usually procured.  It is
employed by paper makers to give  strength to paper, and
likewise by  linen manufacturers, gilders, polishers, &c.
ISINGLASS.
   THIS substance is like  size in transparency,  but it is
much finer, and  is  therefore employed as  an  article  of
food.  It is prepared from the  air, bladders  and sounds
of different kinds of fish,  which are found  in the mouths
of  large rivers.   The  bladder  is  taken  from  the fish,
Washed clean, the exterior membrane separated, cut length-
wise, formed  into  rolls, and then  dried in the open  air.
When good, it is of a white color, nearly transparent and
dry.  It  dissolves  in water with more difficulty than glue,
and it is soluble in ardent spirit.

   A coarse kind of isinglass is prepared from  sea wolves,
sharks, cuttle  fish, whales and all  fish without  scales.—
The head, tail,  fins,  &c. of these are boiled in water,
the liquid  skimmed and strained,   and  again  boiled  till 
DISCOURSE XIII.
377
of the proper  consistence.   It is then cast on flat boards
and cut.   This species is used for clarifying, for stiffening
silk, making sticking plaster, &c.



  GELATINE exists in great  abundance  in  animals.   It
forms a part  of their solids and  fluids.   Blood  and milk
contain it always.  It forms an  essential  part  of bones,
ligaments,  tendons,  muscles, hair, skin, &c.

  Its uses are very numerous.  In the state of jelly it con-
stitutes one of the  most nourishing  and palatable species
of food.  It is the basis of soups.   The  great variety of
purposes to which it is applied in the state  of  glue,  size
and isinglass are well known.
II. OF  ALBUMEN.
  THIS is a substance which exists nearly in a  state of
purity  in  the white of an egg, and in that part of blood
which  remains fluid after it  rests for  some time, and is
called the serum.  When heated  to 165°, it coagulates, or
in other words,  loses its  fluidity, and  then becomes of a
white appearance.  It is also coagulated when any of the
strong  acids or ardent spirit is mixed  with it.   This prop-
erty of assuming the solid state, (or coagulating) by the ex-
ercise of its affinities, in the state  created by the above heat,
is characteristic  of  albumen.
                           3B 
3TS
DISCOURSE XIII.
  When albumen is coagulated, it is insoluble  in water,
and its tendency to putrefy is lessened.  Some other of its
properties are also changed.

  Fluid albumen is soluble in water.   It appears as a glary
liquid, having little taste and no smell.  When  dried in
the  air, or by a slow heat, it becomes a brittle, transparent,
glassy like substance; which when spread thin upon plain
surfaces forms a varnish, and  is accordingly  employed by
book binders for that purpose.  When thus dried, it has a
considerable resemblance to  gum arabic, to which also  it is
similar.  The white of  an egg loses  about four fifths of its
weight in drying.  It continues after  this drying soluble in
water as before.   In this state, it resists putrefaction much
more than in the fluid state.   It unites to tannin like jelly,
forming  an insoluble compound.   Mixed  with  a small
quantity of lime, (particularly the white of an egg) it forms
an excellent lute, which is frequently used to connect to-
gether broken plates, &c.

  Like all other animal substances,  albumen is capable of
existing  in  various  states, both when solid or fluid.   It
forms an essential part of  bone and muscle ;  and the brain
may be considered as a species of it.   Nails, horns, hair,
cartilage,  &c. are  in great measure composed of it;  and
it forms the membranous parts of many shells, sponges, &c.
And, in short, it is one of the most important of the ani-
mal substances.

 • The property  which albumen has of being coagulated by
heat,  renders it  a  very useful substance for clarifying li-
quids.  The serum of blood, white of egg, or any liquid
containing it,  is mixed with  the liquid to be clarified while
cold,  and then the whole  is  heated.   The albumen coagu-
lates, and carries down  with it the floating particles  which 
DISCOURSE  XIJX
379
rendered the liquid opaque.   It is on this principle that the
whites of eggs are added to coffee.
III. FIBRINA.
  THIS is the name of a substance of great importance in
animal bodies.  It may be had in a  state of purity by the
following process :  take a quantity of blood,  newly drawn
from an animal, and on allowing it to rest for some time,  a
thick red clot gradually forms in it, which is generally cal-
led the  coagulum.   Separate the clot from the rest of the
blood, put it into  a linen cloth and wash it repeatedly in
water till it ceases  to give out any color or taste to the li-
quid ; the substance then remaining will be of a white ap-
pearance, and  is that  which chemists call fibrina.  It has
been long known to physicians under the name  of the fi-
brous part of the blood, or coagulating lymph.

   Fibrina is of a white color,  has no taste  or smell,  and is
insoluble in  water  and  ardent spirit.  When newly extract-
ed from blood, it is soft and very elastic, and strikingly re-
sembles the  gluten of vegetables.  It undergoes no change
though kept exposed to the air ; nor does it speedily alter
if kept under water.

   When exposed to heat, it contracts very suddenly, and
moves like a bit of horn, emitting at the same time a smell
like that  of burning  feathers.  In a strong heat it  melts,
and in an intense heat it is entirely decomposed.

   Fibrina exists only in the blood and muscles of animals;
but there are  great varieties of it, as must appear from the 
380               DISCOURSE XIII.
variety in the  muscles of fish, fowl, quadrupeds,  and o-
ther kinds of animals.
IV. OILS.
  THE oily, substances found in animals, in some respects
resemble those obtained from the  vegetable kingdom, and
called expressed  oils.   They differ very much in their con-
sistence from each other, being found in every intermediate
State from spermaceti,  which is perfectly solid, to train oil,
which is  completely liquid.   The most important  of  these
are the following.
1.  SPERMACETI.
   THIS substance is found in a fish called the spermaceti
whale,  and also from others.   At  first it is  mixed with
some liquid oil, which is separated by means of a woollen
bag.  The last portions of  this oil, are separated by means
of a solution of potash or soda in water;  and the sperma-
ceti  is then purified  by fusion.   Thus obtained, it is a
beautiful  white substance, usually  in  small  scales, very
brittle,  has scarcely any taste, and  but little  smell.  It is
distinguished from all other fatty bodies,  by its appearance
in the state of crystals.  In a heat of about 112° degrees it
melts.  When sufficiently heated, it may  be distilled over
without much alteration; but  when  distilled repeatedly, it
loses its solid form, and becomes a liquid oil.  It is soluble
i& boiling alcohol,  but separates again as the solution cools; 
DISCOURSE  XIII.
381
about 150 parts of ardent spirit are necessary for its solu-
tion.   Ether dissolves it cold, and very rapidly when hot;
when  cooling,  the whole  concretes  into a solid mass.
It is dissolved also  in the hot oil of turpentine; but is depo-
sited as the liquid cools.

  When long exposed to the air, spermaceti becomes yellow
and rancid.   In this case it may be purified, by breaking it
into small pieces, and exposing it to the combined action of
the sun and air for some time, by which it loses a great deal
of its  smell, and  acquires a firm consistence.   It should
then be reduced to powder, and a weak solution of  nitrous
acid should be poured on it; in an hour a froth is formed,
and the  acid  is decanted, and the substance repeatedly
washed,  then melted  in hot  water,  and when cool, it ap-
pears of  a beautiful straw color, and* has the  agreeable
smell of  the best spermaceti.

  This substance is very inflammable,  and is employed like
wax and tallow, for making candles.   It was  at one  time
much used as a medicine, particularly in breast complaints.
It is said, that if bits of  elastic gum be added to it while
melted, the gum is dissolved, and the compound  answers
remarkably well for luting vessels together.
2. FAT.
  THIS substance is found abundantly in different parts of
animals.  When pure, it possesses the properties of the thick
oils.  Its consistence  varies from tallow or suet,  which is
brittle, to hog's lard, which is soft.   To obtain fat pure, it 
382
DISCOURSE  XI11.
is  taken from  animals; cut  in  pieces;  well washed in
water, and  the membranous  parts and vessels separated.
It  is then melted in a shallow vessel along with water,  and
kept melted till the water is completely evaporated.  Thus
purified, it is white, tasteless, and nearly liquid.

   Different kinds  of it liquify  at  different  temperatures.
Hog's lard melts at 97° ; but, the fat extracted from meat
boiling, requires, according to Nicholson, a heat of  127° :
when heated to about 400° it begins to emit a white smoke,
which becomes more copious and more disagreeable as the
heat increases ; at  this  time  it  becomes black, owing  to
a  decomposition of a portion of it,  and the deposition  of
some charcoal.  If it be now cooled it becomes more brittle
and solid than the  firs.t.

   Fat is insoluble in water,  alcohol, and ether.  The strong
acids dissolve  and gradually decompose it.    With the al-
kalies it combines and forms soap, as was stated while con-
sidering the alkalies.

   On distilling fat there  is obtained  from  it  an acid  of
which we have spoken, called the sebacic acid.   This acid
exists in fat in such a state of  combination that its presence
cannot be detected.  It is stated  that the solidity of fat de-
pends on this acid.  When the fat is kept in a warm place, it
undergoes changes by which it becomes rancid.  This ran-
cidity is stated to arise from the disengagement of the se-
bacic acid; and this acid is also supposed to be  formed  in
consequence  of  the absorption of  oxigen from the air  by
the mucilage which most fat contains.   However, be this
correct  or not, the rancidity  may  be corrected by mixing
the fat well with  large quantities of hot water,  or  ardent
 spirit:  cold water  impregnated with carbonic acid and pow-
 dered charcoal are said 'to have  the same effect.  Marrow
 differs  very little in its nature from fat. 
DISCOURSE  XIII.
383
III. TRAIN OIL,
  THIS liquid is extracted from the blubber of .the whale,
and from other fish.  It forms a very important article of
commerce, being employed for combustion  in lamps, and
for other purposes.  It  is at first thick, but on standing, a
white mucilaginous matter is deposited and the  oil becomes
transparent.  It is then  of  a  reddish brown color, and has
a disagreeable smell.

  Various methods have been employed for  purifying train
oil.   The purification can be effected by agitating it with
a little sulphuric acid, and then adding a little water.  The
oil  when allowed to settle swims on the  surface,  of a
much lighter color than before,  the water appears milky,
and a turbid matter is observed swimming between the oil
and water.

   Spermaceti oil. This is the oil which is separated from sper-
maceti during its purification.  It is much purer than train
oil, and, therefore,  answers better for lamps.
IV. ANIMAL OIL OF  DIPPEL,
  THIS is an oil once of great celebrity  among  the an-
cients.  It is usually called as  above.   It is obtained by the
distillation of the soft  parts  of animals, and also from
horns.  The product of the  first distillation is to be mixed
with water,  and distilled with  a moderate heat again. 
384
DISCOURSE  XIII.
   This oil is colorless and transparent; its smell is strong
and rather  aromatic.   It is almost as light and volatile as
ether.  The  alkalies unite to it, forming soap; nitric acid
sets it on fire.  It was formerly used as a remedy for  fevers.
It contains a little ammonia, in consequence  of which, it
changes blue vegetables to a green.
   ALMOST the whole of the soft parts of  animal  bodies
consist of the substances we have described; namely, gela-
tine, albumen, fibrina and oil.   However, there have been
found several other substances,  which must  be considered,
although they have not been found  in  considerable quan-
tities.  The most remarkable are the following.
AMBERGRIS.
   THIS is a substance found floating  on the sea near the
 coasts of India, Africa and Brazil, usually in small pieces,
 but  sometimes in masses of 50  or  100 pounds weight.
 Various opinions have been entertained concerning its ori-
 gin.   Some have affirmed that it was the concrete juice, of
 a tree;  others thought it a bitumen; but it is now generally
 considered  as a concretion  formed in the stomach or intes-
 tines of the spermaceti whale.

   Ambergris when pure,  is a light soft substance which
 swims on water.   Its specific gravity is about 0.845.  Its
 color is ash grey, with brownish, yellow and white streaks.
It has an agreeable smell, which improves on keeping.  Its
taste is insipid.  It is insoluble  in water.  Both the fixed
and volatile oils, and also  ether and alcohol dissolves it.
* 
                  DISCOURSE XIII.               385
                       CASTOR.

  THIS substance is obtained from the beaver.   In the
groin of that animal, there are two bags,  a  large  and a
small one.   The large one contains the true castor.   When
first procured it is nearly  fluid;  but by exposure to the air,
it gradually hardens,  becomes darker colored, and assumes
a resinous  appearance.   Its taste  is bitter and acrid,  and
its odour strong and aromatic.   It is used as a perfume.


                       CIVET.

   THIS substance, like the last, is obtained from the groin
©f the  civet cat.   It  is squeezed out of the cavity where it
is  secreted  every other day.  It is employed as a perfume,
but has not hitherto engaged the attention of chemists.   Its
color is yellow.    Its consistence that of  butter;  and its
smell is so strong that it is only agreeable when reduced by
mixture with other bodies.


                         MUSK.

   THIS  substance is secreted in a kind of bag,  situated
about the navel of  a  quadruped,  called muschus maschifer.
Its color is brownish  red.   It feels greasy.  Its taste is bit-
ter.   Its smell aromatic and very strong.   It is  soluble in
ardent spirit, but it then loses its odour.   It is partially solu-
ble in water, and it then  retains its odour.   At a red heat
it  smells like urine.   It is chiefly used as  a perfume, and as
a  medicine.  In hysteric  and other nervous affections, it is
given in repeated doses of three or four grains.
« 
386               DISCOURSE XIII.

                       SUGAR.


  SACHARINE matter has frequently been found in the
fluids of animals ; not however in the state of common su-
gar.   This animal sugar, if it may be so called, is found in
milk, and in the urine of persons laboring under a disease
called diabetes.


                 SUGAR  OF MILK

  MAY be obtained by the following process :  Let fresh
whey be evaporated to the consistence  of honey,  and  then
allowed to cool.   It concretes into a solid mass.  Dissolve
this mass in water, clarify it with the white of eggs; strain
jt and then evaporate it to the consistence of a syrup.  On
cooling, it will deposit a number of  brilliant white crystals,
which are sugar of milk.

  When pure,  it has a white color, a sweet taste, and  no
smell.   Its specific gravity is 1.543.  At a temperature  of
55 it is  soluble in seven times  its weight of water; but it
is perfectly insoluble in ardent spirit.   When burnt it ex-
hibits the same appearances as common  sugar,  and by dis-
tillation the products of  each are found nearly the same.


                 SUGAR OF URINE

  MAY be obtained, by collecting considerable quantities of
the urine of persons laboring under the disease called di-
abetes,  and evaporating it to the consistence of honey,  as
above.    Mr.  Cruickshank extracted  from some diabetic
urine one  twelfth its  weight of a sweet tasted extract
like honey.  When heated with nitric acid,  it yielded the
* 
DISCOURSE  XIII.
387
same products that common sugar did.  But it could not
be made to crystallize, and when added to lime it  is de-
composed,  which is not the case with common sugar.

  Besides the substances above named, • several others have
been obtained from various animals,  particularly of the in-
sect  tribe,  which are  distinguished  by remarkable proper-
ties.   Cantharides, ox Spanish flies, are among the most im-
portant.   This insect,  when rubbed up and applied to the
body, is universally known to excite irritation and blisters.
This is the  property by which they are distinguished.—
When taken internally, they operate very violently in small
quantities, and appear to produce a particular determination
to the urinary organs.  However, in small  quantities, dis-
solved in ardent spirit, (forming the tincture of cantharides)
they form  an useful medicine.   There is a bug common  in
this  country, and which is found particularly about potatoe
Vines, very much like the Spanish fly in its effects on the
Dody.   It is substituted for the fly in many  parts, and from
the  cost of the  fly,  it  is hoped  that this  practice will
become general.   This bug can be collected in botdes, and
kept for use.

   The article of commerce sold by the term cochineal, is also
an insect obtained chiefly from Mexico and St. Domingo.
It is dried, and preserved for the use of dyers, as is univer-
sally known.  Lac, or gum lac, is also an animal substance,
collected by red winged ants in the East Indies.   It is used
in coloring sealing wax, and other  bodies.  But  it  is not
consistent with the plan of this work,  to enter into a parti-
cular detail of such substances.

   The following acids  have also been obtained from the
 animal kingdom.   As they are not of  much consequence,
 it will be useless to dwell on them, 
38«              DISCOURSE XIII.
1. PRUSSIC ACID.
   OF this we stated all that was of any consequence when
considering its combination with iron, forming the prussiate
of iron,  or Prussian blue.   The acid,  as before observed,
is  formed by the decomposition of animal parts with pot-
ash in a strong heat.  Its combination with other substan-
ces, forming prussiates, have not been attentively examined,
and it is difficult to form them.
2. LACTIC ACID.
  THIS acid exists in the whey of milk.   On evaporating
the whey, its taste will be perceptible.   With other bodies
it forms lactates, of no known importance.
3.  SEBACIC ACID.
  THIS acid is obtained by the distillation of hogs lard
with hot water.  The acid comes over.  When it unites to
jplher bodies, it forms compounds, called sebates.


                   4. URIC ACID.
  THIS acid is obtained from human urine : it also exists
in the calculi obtained from the  bladder, and from gouty 
                  DISCOURSE XIII.              389
concretions.  It is scarcely soluble in water :  it may readily
be decomposed by a strong heat.   It unites to other sub*
stances,  forming  urates,  which are of no known  value.
However,  it has been  ascertained, that the  calculi of the
urinary bladder are very generally composed of a little mu-
cilage with the urate of potash or soda.  The urate of soda
also  forms the concretions found in persons affected with
gout; these  were commonly called chalky concretions, in
consequence  of their  being mistaken for preparations of
lime.  It is to Drs. Wollaston and Pearson that we are in-
debted for this information.




                 B.  AMNIOTIC  ACID.
  THIS is  obtained by evaporating the fluid  which sur-
rounds the calf in the womb of the cow.   It has not been
much attended to, as well as several other acids, such as
the bombic acid, said to be obtained from the silk worm, and
the formic acid, said to be obtained from ants.
   THE various bodies which compose animal parts, have
been commonly arranged under the two heads of hard parts
and soft parts.  The hard parts of animals are principally
the following : bones, horns, nails, muscles,  skin, membranes,
tendons, ligaments, glands,  brain,  nerves, hair, feathers, and
silk ; of which we will treat in the order in which they are
named. 
3.9.0
DISCOURSE XIII
OF BONES.
   THE bones are the most solid parts of animals;  their
 texture varies  according to  the situation of the  bone.
 They are white, appear to be formed of plates, and cannot
 be softened by heat.   Their specific gravity differs in differ-
 ent parts.   That of adults' teeth is 2.2727: the specific
 gravity of children's  teeth is 2.0833.   It must have been
 always known that bones are combustible ; and that when
 sufficiently burnt, they leave behind them a white porous
 substance, which is  tasteless, absorbs water, and has the
 form of the original bone.

   The component parts of bone are chiefly four :  namely,
 the earthy salts, fat,  gelatine and cartilage.

   1. The earthy salts may be obtained, either by burning
 the bone till it becomes white, or by  steeping it in acids.
 In the first case,  the  salts  remain in the state of  a brittle
 white substance.   In  the second, they are dissolved by the
 acids,  and may be precipitated by adding an alkali.  These
 earthy salts are three in number: 1, the phosphate of lime,
 which constitutes by  far the greatest part of the whole :
 2, carbonate of lime,  or chalk: 3, sulphate of lime, which
 is found in much the  smallest quantities.

   2. The proportion  of fat contained in bones is not less
 various.   By  breaking the bones  in small pieces and boiling
them for some time in water, this fat will be found swim-
 ming on the liquid.   It is stated, that  by these means one
 fourth of the weight  of the bones will be  found to be fat.
 This is a much larger quantity of  fat than is commonly had 
DISCOURSE  XIII.              391
from them, and in all cases it must appear, that it would be
found of advantage to break the bones before boiling them.

   3. The  gelatine is separated from bones by the  same
means as  the fat, by breaking the bones in  pieces, and
boiling them long enough  in water.  The water dissolves
the gelatine; and when evaporated in part, it  is converted
into a jelly.  Hence the importance  of bones  in making
portable  soups and  glue,  the  base of which is gelatine.
About one tenth of the weight of bones is found to be ge-
latine.  It is stated  that pounded bones, long boiled, will
make as good soup as four times their weight  of flesh; or
if they be not pounded,  they should be  boiled in Papin's
digester.

   4. When bones are deprived of their fat and gelatine by
boiling them in water, and of their earthy salts by steeping
them in  diluted acids, there remains  a soft, white, elastic
substance,  possessing the figure of  the bones,  and known
by  the name of cartilage.   This  substance  is  found to be
nothing more than coagulated albumen; brittle and nearly
transparent when dried ; soluble in hot water, and is  con-
verted into jelly on cooling.

  This cartilaginous substance is  the  portion  of the bone
first formed.  Hence the softness of the bones of  young
animals.   The phosphate of lime is afterwards gradually
deposited,  and gives the bones the requisite firmness.  The
gelatine and fat, especially the first, give the bone the
requisite degree of toughness and strength ;  for when  they
are removed the bones become brittle.  The relative  pro-
portion of  phosphate of lime and cartilage differ in different
bones,  and in different animals.   The only part  of a bone
found destitute  of cartilage, is the enamel of  the teeth. 
392
DISCOURSE xnr.
However the teeth of adults is found generally composed
as follows:

            64 parts phosphate of lime,
             6  do.  carbonate of  lime,
            20  do.  cartilage,
            10  do.  loss.

           100

   The bones obtained from a great way beneath the earth,
are called fossil bones.  According to Dr. Hatchett's exam-
ination of  those procured from Gibraltar do not contain any
cartilage, or soft animal part.  Their cavities are filled with
the carbonate of lime.  Hence, they resemble bones which
are burnt.  Putrefaction does  not  destroy the cartilaginous
part  of bones: hence, Mr. Hachett found, on  examining
bones taken from a Saxon tomb, that they contained as much
cartilage as fresh bones.  Now, in consequence of this, it is
exceedingly probable, that the bones dug out of the earth,,
of particular shapes, are  not really the  bones of animals,
but are crystallizations of lime, or some of its preparations,
which were in some measure accidentally  formed.   This is
rendered still more probable from  the crystallizations fre-
quently found in caves, having very striking resemblances
to several of the preparations of art.  It  must appear very
evident that the  particles of matter coming together in the
earth would  there exercise  their affinities peculiar  to  the
state  in which they were placed; and we know that this
state may  be changed ten thousand ways by the  electric
fluid as it passes through; and, in fine,  by any substance.
At least, this supposition appears less objectionable  than
those that the earth  was once inhabited by  an uncommon
race  of animals ;  that all these animals died,  and that the
earth burst open, and received the bones"; or, that the sea 
DISCOURSE  XIII.
393
 inundated the land, and deposited the earth on those bones.
 All this, however, is only conjecture.

   Nearly allied to the bones of animals are the  shells,  or
 hard coverings of many of them; such  as those of fish,
 egg  shells,  &c   Shells,  like  bones,   consist  of  lime,
 united  to carbonic acid, whereas in bones it is  united to
 phosphoric acid.  The characteristic difference then between
 shells and bones, consists in this, that the chief ingredient
 of shells is chalk, or carbonate of lime; and the  chief in-
 gredient of bones is phosphate of lime.   These shells may
be decomposed by means of an intense heat,  and converted
 nearly in the state of pure lime, as  we daily see practised
 with oyster shells.

  The compositions of the  crusts of animals as  they are
called, is nearly the same as that of the shells: in some in-
stances, however,  they contain more of the phosphate of
lime.  All the inflexible,  or  hard parts  of  animals,  may
 with propriety be considered  as formed  chiefly of either
the carbonate or phosphate of lime; and they may all be
decomposed nearly by the same means.  Some  of  them
are used as medicines, as common chalk.
HORNS  AND SCALES.
  THESE hard parts of animals are distinguished from the
above, by a  considerable  degree  of elasticity; by being
softened by heat,  and by containing but a  small portion of
lime.   This set includes the substances  known under the
names of horn, nails and scales.
                         3 D 
394
DISCOURSE XUI.
  1  Horns, are bodies universally known to grow trom the
foreheads of oxen, sheep and various other animals. They
are  not  very hard, as  they may easily be cut  with  a knife,
or rasped with a file;  but they are too tough to be pounded
in a mortar.  When in  thin plates, they have a degree of
transparency, and in this  state have  been substitued for
glass in windows.  When  sufficiently heated, they become
Very soft and yielding,  so  that their shape may be altered
considerably, as  is well known: this  is  facilitated  when
dipped in hot water;  by this means combs are  made  from
CjWs'  horns in  many  country places.   When  strongly
he. ted  in   Papin's digester, it is  said they are converted
 into a gelatinous mass.

   The  quantity  of earthy matter which they contain, is
 very inconsiderable.   They consist chiefly of a membran-
 ous substance, which  possesses  the  properties of coagu-
 lated albumen, and probably they contain a httle gelatine.
 Hence  we see  the reason why ammonia  or the volatile al-
 kali is obtained,  when  these substances  are  submitted to
 Strong distillation.

   However, the horns  of  the hart and buck form excep-
 tions to the above statement.  They are  found to  differ in
 their composition from bone, only in containing  a  larger
 quantity of cartilage.

    2. The nails, which  cover the  extremeties of the fingers,
 are attached to the skin, and come off along with  it.  They
 are composed  of a membranous  substance,  which posses-
 ses the properties of  coagulated albumen.  Water softens,
 but does not  dissolve them.  They are  readily dissolved
 and decomposed by concentrated acids  and  alkalies: and
 they agree  very much in their composition with horns.   Of
 this kind,  are the talons and claws of inferior animals, and
 likewise their hoofs,  which do not differ from horn. 
DISCOURSE XIII.
395
   The substance called tortoise shell is very different from
 shells in its  composition, and approaches much nearer to
 the nature of nail.   When long kept in the nitric  acid, it
 softens and appears to be composed of membranes laid over
 each other,  and possessing the properties of coagulated al-
 bumen.

   3. The scales of animals are of two kinds : some of those
 of serpents, and other amphibious animals have a striking
 resemblance  to horn; and  also the horh-like  substances
 which cover certain  insects.  The other  kind,  called the
 scales of  fish, are found different in their  composition.
They contain a considerable  quantity of  the phosphate of
lime.
OF THE MUSCLES OF ANIMALS.
  THE muscular parts  of animals, are known in common
language by the texm flesh.   They constitute a considerable
portion of the food of men.  Flesh is composed of a great
number of  fibres  or threads, commonly of a reddish or
white  color, as  is well known.   It is scarcely  possible
to separate  it from all the  other  substances with which
it  is mixed.  A  quantity  of  fat adheres  to it  closely;
blood pervades the whole of it, and every fibre is  envel-
oped  in a particular thin membrane, called by  anatomists
cellular membrane.   Of  course, the  decomposition of the
flesh or muscle connot be supposed  to  exhibit an  accurate
view of the  composition of pure muscular fibre. 
396               DISCOURSE XIII.
  When a muscle is cut in small pieces, and well washed
in cold water,  it is converted into a white fibrous substance,
which retains the form of the original body.   This  water
when evaporated is found to contain some  alumine, and a
particular substance called extractive matter . If the muscle
after this be boiled for a sufficient time in hot water, an ad-
ditional portion of the same substance is separated from it,
with a  quantity of fat  and albumen.   The muscle thus
treated with water, is left in the state of grey fibres, inso-
luble in water, and brittle when dry.  This substance pos-
sesses all the properties of fibrina ;  and the water is found
to contain a number of salts.   According to  Thouvenel,
andFourcroy, the muscles contain the following substances :
 1. Fibrina. 2. Albumen.  3. Phosphate of soda.  4.  Ge-
latine.  5. Extractive matter. 6.. Phosphate  of  ammonia.
7. Phosphate  of  lime.  8. Carbonate of lime.

   The  two first of these substances, it is known,  are com-
posed of  great quantities of  nitrogen. Hence,  when nitric
acid is poured on  flesh, great quantities of nitrogen air are
extricated.

   The  muscles  of  different  animals differ  exceedingly
from each other in their appearance and properties, at  least
as articles of food, but little  is known concerning their
chemical  differences.

   When meat is boiled it is  obvious  that the  gelatine, the
 extractive, and a portion of the salts,  will  be separated,
 while  the coagulated albumen and fibrina  will remain in a
 solid state.  Hence the  flavor and  nourishing  nature  of
 soups.   When meat is roasted, and particularly when  its
 Surface is suddenly exposed to a strong heat, so as to coag-
 ulate the albumen and prevent the exit of  the juices, then
 its taste  and  odour is much exercised.   The heat acts ae 
DISCOURSE  XIII.
397
before observed, only by creating states in which the affinities
of the particles of the meat are differently exercised, so that
palatable combinations take place.

  Meat, it is well known has a remarkable tendency to un-
dergo changes within itself, called putrefaction. Many attempts
have been  made  to retard this progress ; and  several suc-
ceed in preventing it at least for a considerable time.

  The freezing temperature is a complete preservative from
putrefaction, as long as the animal bodies are exposed to it.
Hence, die  common practice of keeping meat in  snow in
the  frozen climates  of the north ;  and, also,  of  packing
fish up in it,  and sending them to market.

   It is well known that common salt prevents putrefaction
in large quantities ; but it is found to quicken it when the
 quantity is but small.  Several other salts, especially nitre,
 possess the same property.  The acids, particularly the car-
 bonic acid in the state of air or mixed with water,  syrup,
 ardent spirit,and many aromatic substances,such as camphor5,
 resins,  volatile oils,  bitumens, &c.  also act with consider-
 able  efficacy in  preventing flesh from putrefying.   Hence
 these last substances  are used in embalming the  dead  bodies
 of some persons.

   Besides these  methods of preventing putrefaction,  the
 bodies  are frequently preserved by placing them  in situations
 where their fluid parts are carried off.  The Indians  parti-
 cularly, preserve their flesh by suspending it in chimney
 corners, where the hot smoke conducts off the moisture.
 In some instances, the bodies of men have been buried in
 dry earth, which rapidly absorbs the moisture of the bodies,
 and  in consequence of this, the carcases become  dry, and
 are transformed into what are called mummies. 
398               DISCOURSE XI11.
  The theory to explain these facts is not quite satisfactory.
However, as observed by Dr. Thompson, it is very prob-
able that these substances solely prevent putrefaction, by de-
priving animal parts of their water.  It is well known that
for putrefaction  to  take place the presence  of  water is
necessary.   Now when  salt, and  such bodies are rubbed
on meat, they unite with the water and form with it a new
compound, which differs very much from common water.
Of course then the bodies cannot putrefy until they absorb
water from the air.   There is no doubt but that the bodies
preserved by drying  them, owe  their preservation to being
deprived of that water  necessary for  putrefaction to take
place.
OF THE SKIN.
  THE skin is that strong thick covering which surrounds
the bodies of animals.   It is well known, that the skins of
different animals differ very considerably in several respects,
and that even the skin of  the same animal is not equal in
its composition.  What is commonly  called skin, consists
of two very different substances joined together; yet they
may be separated very readily from each other, when kept
in putrefying water for several days.  The exterior or outer
part may,  by maceration in water,  be  obtained from com-
mon skins; it  is called by anatomists cuticle, or  epidermis;
and it is that part which rises up when blisters are formed
on  the  body.   It is  remarkably elastic, and is  not pos-
sessed of  sensibility.   But little  is known  concerning  its
nature of any  consequence.   When the nitric acid  is ap-
plied  to it, and particularly if a little  ammonia be  after-
wards applied,  it is tinged of a deep orange color, just as 
DISCOURSE  XIII.
399
coagulated albumen is.  This  has led  to  the  conclusion,
that it is albumen a little modified.

  The interior part of the skin differs very much from the
above.   It is called cutis.   It appears composed of  fibres,
interwoven  like  the texture of a  hat.  When distilled, it
yields the same products as fibrina.  When boiled in water
for a long while, it is dissolved, and is converted into  ge-
latine or glue, of  which we have treated.  Hence  it  ap-
pears, that the cutis is nothing more than a peculiar modi-
fication of  gelatine, which  resists  the action  of  water in
consequence of  the compactness  of its texture.   It is this
part  of the  skin which unites  to tannin and  forms leather.
Of the  method of  tanning leather,  we treated when con-
sidering tannin.
OF MEMBRANES, TENDONS, LIGAMENTS
                AND GLANDS.
  THESE substances have  not been much examined by
chemists.   The following is stated concerning them.

  1* Membranes.  These are thin semi-transparent bodies,
which cover certain parts of the body, especially in the ab-
domen or belly.   The thin coat usually pulled from hog's
lard, is one of this kind.  Membranes are soft and pliable.
When  dissolved in hot water, they are converted into gela-
tine; and when kept  in  an infusion of tannin they are
converted  into leather.  Hence they resemble  skins very
much. 
400
DISCOURSE  XIII.
  2. Tendonj.  These are strong, pearl colored,  brilliant
bodies,  which terminate the muscles and attach them to the
bones :  they  are  commonly called  sinews.  When  boiled
they assume the form  of a gelatinous substance, of a plea-
sant taste, as  observed in parts of boiled meat. Its compo-
sition,  therefore,  resembles that of  skins.

  3. Ligaments.   These are strong bands which  bind the
bones together at the different joints.  They resist the ac-
tion of  water, and possess  a great  deal of elasticity  and
strength.   They  contain  some gelatine,  but differ very
much from skins.

  4.  Glands.   These are a set of bodies,  employed to
form the different liquids or secretions found in animals ; as
the liver,  kidneys, glands  of the  brain, &c.    It  is very
probable that they differ but little in their composition from
muscular fibres,  as they are formed of  fibres.
OF THE BRAIN AND  NERVED
  THE brain and nerves are the instruments of sensation
and life : they strongly resemble each  other.  The brain
has a soft feel, not unlike that of soap ;  its texture appears
to be very close;  its specific gravity is greater than  that of
water.   When distilled it yields much volatile alkali, as also
when pure potash is added to it.   It  appears to contain  al-
bumen ; but, upon the whole, differs materially in its com-
position from other parts of the body. 
                  DISCOURSE XIII.             401

            OF HAIR  AND FEATHERS.


   THESE substances cover different parts of animals, and
appear designed by nature to defend them from the cold.
Their pliability and softness, and their resisting the passage
of heat, adapts them  for this purpose.

   Hair is usually distinguished into various kinds, accord-
ing to its size and appearance.  The stiffest is called bristle;
when fine it is  called wool;  and when very fine it is called
down.   In their composition, however,  they resemble each
other.

   On examination with a magnifying glass, hair appears as
a tube with a cover.   Its surface is not  smooth, as must be
evident from the roughness  of its feel; and the  tendency
it has to entangle itself, has given rise to the process of felt-
ing and fulling.   It contains gelatine, to which it  owes its
suppleness and toughness.  This substance may be separa-
ted by boiling; and  then the hair becomes very brittle.

   The  rapidity with which hair burns, and its  fusion  at
the time,  is known to every one.   When subjected to de-
structive  distillation, Berthollet states  that the following
products were obtained from  1152 parts of it:

               90 carbonate of ammonia,
              179 water smelling of burnt hair,
              288 oil of  a brown color,
              271 airs,
              324 coal attracted by the magnet.
1152.
              3E 
402
DISCOURSE  XIII.
  The alkalies dissolve hair at a boiling heat, and form with
it an animal soap.  When muriatic acid is poured on  a so-
lution of it in potash, sulphurated hidrogen air is extricated ;
hence it contains sulphur.  The nitric acid tinges it yellow,
and the nitrate of silver washes it black.

   Feathers seem to possess very nearly the same properties
with hair.   The quill is composed chiefly of coagulated al-
bumen.   It is customary to boil them in oils abroad b#fore
they are made into pens for writing.
OF SILK.
   THIS is the last of the hard parts of animals we have
 to consider.   It  is the production of different species  of
.caterpillars.   It is found inclosed in two small bags, from
 which it is protruded in fine threads to serve the insect for
 a covering during  its young state.   The webs of spiders
 are  of  the same nature with silk,  though their threads are
 finer and weaker.   Naturalists have ascertained, that the
 larger kinds of spiders, spin webs sufficiently strong to be
 manufactured ; and that the produce was equal in beauty
 and strength to the silk of the silk worm.  In  consequence
 of  this attempts were made to establish a manufactory of
 this new kind of silk; but it was found that the spiders
 would  not work in concert.  They attacked and devoured
 each other  without mercy, till  the whole colony was de-
 stroyed to an individual.

   The  silk worm is a native  of China,  and feeds on the
 leaves of the white mulberry.   It spins the silk in the state 
/
                   DISCOURSE XIII.              403
<of  fine threads, varying  in color from white  to  reddish.
It  is very  elastic, and  has  considerable  strength, if  its
diameter be taken  into  consideration.   It is covered with
a varnish, to which it owes its elasticity.   This ^Tli'isa is
soluble in boiling water,  and when the water is evaporated
it  is obtained  of a black color, brittle, and  of  a shining
fracture.  Its weight is  nearly one  third of the raw silk,
from which it was extracted.   It may be separated  from
silk by soap as well as water.

   Besides the varnish,  silk contains a substance like  resin,
to  which it owes its yellow color.    It is soluble in ardent
spirit, and in a mixture of ardent spirit and muriatic  acid :
this mixture leaves it of a fine  white color.   And in conse-
quence of  this it may  very  advantageously  be  used  for
bleaching the common yellow  silks.  For this purpose it is
only necessary to mix together four parts of ardent spirit,
and one of muriatic acid.   The silks are  to be kept two or
three hours  in warm water, and should then be introduced
in the mixture,  and kept  there for ten or fifteen hours.   It
should then be washed in water, and again kept in  another
mixture about the same time.   If the mixture be warmthe
operation may be shorter. The silk should then be kept in
spirit alone  a few hours, and then must be repeatedly wash-
ed  in common water.

   The  properties of pure silk have been but imperfectly ex-
amined.  It is not acted on by  water or spirit; it is tasteless,
and burns badly, but the fire rapidly turns it of a black color.
When  distilled it  yields  large quantities of  ammonia.   It
is not very  susceptible   of putrefaction unless when in  a
damp place, and then it readily rots, to use a cpmmon  ex-
pression. 
DISCOURSE  XIV.
  HAVING given  the  preceding account of the solids of
animals,  I proceed to consider the  remaining parts,  which
come under the head of soft parts.  The most important
of these  are blood,  milk, bile,  gastric juice, urine, poisonous
secretions, saliva, and all the other fluids formed from the
blood which are called secretions.
OF BLOOD.
  THIS is the well known fluid which circulates through
the arteries and veins of animals, and of which all animal
parts are formed.  It is of a red color, has a considerable
degree of consistency, and an oily feel.   Its taste is slight-
ly saline, and it has a peculiar smell. 
DISCOURSE  XIV.               405
  When blood, after being drawn from an animal, is allow-
ed to remain some time at rest,  it very soon undergoes a
change ; one part of it separates from the rest, and forms a
clot, while the rest is more fluid,  and has the appearance
of water.   This process is called coagulation,- the clot is
called the coagulum,  and the remaining part is termed the
serum.  This separation is similar  to the conversion of milk
to clabber.

  The proportion between the clot and the serum  varies
very much  in  different  animals, and  indeed in  the same
animal at different times.  The most common proportion
is that of one part of the coagulum to three parts of serum.
This coagulation of  blood takes place in open vessels, and
in the open air, whether the  temperature be increased or
diminished,  or the blood diluted or not with water.   It has
been attributed by Mr. John Hunter and his followers to a
 vital principle, but I do not  see  why it should not be con-
 sidered as a law of the blood, by which  its particles of a
 certain kind come together.

   The fluid which  remains, called the serum, is of a light
 greenish yellow color.   It has the taste and smell and feel
 of blood; but it is not so thick.   It converts the syrup of
 violets green, and  therefore contains an  alkali; which is
 found to be soda.  When heated to the temperature of 165°
 it coagulates,  like the white  of an egg,  into a hard mass,
 from which however,  some  fluid, chiefly water, may be
 obtained.  This mass is found to be possessed of all the pro-
 perties of coagulated albumen.

    Besides albumen, the serum is found to contain gelatine,
  which will appear by  boiling it in six times its weight of
  water, and then gently evaporating the fluid. 
406
DISCOURSE  XIV.
   If this serum be heated  in a  silver  spoon, the surface
 of the silver will become black, in consequence of its uni-
 ting to sulphur, obtained from its contents.   Hence serum
 contains sulphur.

   If the serum of the blood be mixed with water  and co-
 agulated by heat; and if the fluid  parts remaining be eva-
 porated considerably,  on laying it aside to cool,  a number of
 crystals will appear, which are found to consist of the car-
 bonate, phosphate, and muriate of  soda with the phosphate
 of lime.  And thus it appears that the serum of the blood
 contains albumen, gelatine, sulphur, soda and muriate, and
 phosphate of soda, and phosphate of lim e.

   The coagulum, or  clot, is of  a red  color, and possesses
 considerable consistence.  If this be washed very carefully
 in water for a long time,  it loses its coloring matter, and
 appears of a white  color, possesses elasticity,  and in fact
 is fibrina, the substance we have described.

   If the water in which the blood was washed be preserved,
 evaporated  and examined,- it  will be found to  contain
 an oxid of iron on which its color much depends,  and also
 a small quantity of albumen and  soda.  The oxid of iron,
 it is stated, exists  in combination with the phosphorous acid
 forming  a phosphite of iron, which  is of a red color, and
 soluble in serum.

   When new drawn blood is stirred briskly round  with the
hand or a stick, the  fibrina  or coagulum collects  on the
stick, and may  be separated from the rest of the blood.—
The red part in this case remains behind in the serum.  It
is in this manner, that blood is  prepared for the different
 purposes to  which it is applied, as clarifying sugar, making 
                  DISCOURSE XIV.             %07
puddings, &c.   When thus treated, the blood does  not
coagulate on resting.

  Blood then appears to be a very compound fluid, is com-
 posed of no less than ten different  substances; to  wit.—
 1, Water; 2, fibrina;  3, albumen; 4, gelatine; 5, sulphur;
 6,  soda;  7,  phosphate  of iron;   8,  muriate of  soda;
 9,  phosphate of  soda, and  10, phosphate of lime.

  The  blood,  as before  observed,  is subject to very great
 changes.   In the arteries it is of a  bright color, which it
 received from its union with oxigen in the lungs.   In the
 veins it appears much darker; and sometimes almost black,
 as  it runs from their orifices.  On  exposure, however, to
 air, it loses this  dark color, in consequence of absorbing
 oxigen;  and  appears as bright as that obtained  from the
 arteries.

   It has long been known,  that blood drawn from a per-
 son laboring  under inflammation, is soon covered with  a
 white crust,  which physicians Call  the buffy coat.   This is
 found to be nothing more than the fibrina  of the blood,
 which before  coagulation,  allowed  the  coloring matter to
 subside.

   During the disease called  the  diabetes,  in which the
 urine is excessive in quantity, and  has  a sweet taste^ the
 serum of the blood is stated by Dr. Rolld to assume the
 appearance of whey;  and loses its salt taste.  However,
 in  some very remarkable diseases, such as putrid fever and
 scurvy,  it has been found that the blood undergoes no
 change, which adds to the many  proofs, that it is wrong
 to  attribute diseases to the  state of  the blood. 
408
DISCOURSE XIV.
                      OF MILK.


  MILK is a fluid formed  in females, for the nourish-
ment of their offspring.  In different animals,  it is distin-
guished by  different peculiarities.  But the  animal whose
milk is most  used by man, is  the cow ; with its  properties
we are best acquainted, and therefore we will  consider this
first.

  The milk of the cow is  known to be a white fluid, to
possess a slight peculiar smell,  and a pleasant sweetish taste.
When just drawn from the cow,  it has a taste very differ-
ent from that which it acquires after standing for some time.
It boils at the temperature of boiling water; it is specifically
heavier than water,  and lighter than  blood  ; it has an oily
feel.

  If fresh milk be left to rest  for some time,  in a cool si-
tuation it undergoes a change.   In the first  place, there
arises on the surface a thick substance called cream. When
this is removed the remainder is termed skimmed milk, which
is of a blueish cast, and is more fluid than before.   Some
time afterwards, particularly if in a warm temperature and
exposed to fresh air, it separates into a solid, called clabber,
or curd, which when removed, leaves the fluid called whey.

   This separation of milk into curd and whey, may be ef-
fected by the addition of other substances,  such as the
strong acids, several vegetable substances, and particularly
by the stomach of calves, called  the rennet,  which is used
in the preparation of cheese.

   Cream.   This part of the milk, which is  the  lightest,
 and consequently rises to the surface,  contains  an oil, which 
DISCOURSE  XIV.
409
on being exposed to the  air, and churned is converted into
an hard substance, butter, which we will presently consider.

   Curd.   This  coagulated part of  milk,  when  fresh,  is
a  white  substance,  somewhat elastic;  but  is of more
or less consistence  according  to  the  quantity of  whey
it contains.   It is insoluble in water, becomes hard in  hot
water, and is readily dissolved  by the acids.  When salted
and compressed,  it forms the well known article, cheese, to
be considered hereafter.  In some of its properties curd xer
sembles albumen.

   Whey.   This fluid, which remains after the separation of
the cream and curd, is  of a   yellowish color,  and has a
sweet agreeable  taste.  It is always turbid,  and is best cla-
rified by the white of eggs.  It is called sweet whey. It ij
sometimes used in medicine, and is prepared by adding half
a dram of powdered cream of tartar,  or a  few tea spoons
full of lemon juice to a  pint of milk,  brought to the boil-
ing point, and  kept so till the  coagulation of  the curd  is
complete.   It is then clarified by white of eggs, and depri-
ved of its sourness by a little chalk.    An agreeable drink
is sometimes made by adding  five or six ounces of good
sour white wine to a pint of boiling milk,  and then strain-
ing the whole.

   Whey  is  used in the bleaching of linen.  The linen is
left eight or fifteen days  in large  vessels containing  this
fluid,  and when taken out it is perfectly  bleached.  In this
case it is the acid  of the whey which destroys the coloring
matter of the linen.

   If die whey of milk be evaporated, there will be obtained
crystals of sugar, which  are called the  sugar of milk.  This
                           3F 
410              DISCOURSE XIV.
gives it the power of  undergoing the vinous fermentation,
and forming an intoxicating liquor of course.  If on the con-
trary,  milk has become  sour  before coagulation,  the li-
quor that remains is called sour whey.  Sweet whey, by rest,
will undergo the acetous  fermentation  and become sour:
particularly if a  small quantity of ardent spirit be  added.
This  acidity is attributed to a particular acid, called  the
lactic acid.   In some instances the whey is found to contain
aai oil, when obtained from cheese just made.  Besides su-
gar and sometimes an acid, whey contains other substances,
particularly some of the preparations of  lime, as the phos-
phate,  sulphate,  and  muriate of  lime,  and sometimes
common salt.  These may be procured by evaporating the
whey.  The proportion of water in whey is very consider-
able ; and, in fact, it is stated by Dr. Young, that upwards
of  seven eights of  common milk is nothing more than pure
water.


   Milk  therefore contains, according to the above state-
 ment, an  oil;—curd, whey, or  water  holding in solution
 several neutral salts.

   It is  with the utmost difficulty that new milk will pu-
 trefy.  Hence it is frequently used to impart an agreeable
 taste to wines.   However,  it is very susceptible of the
 acetous  fermentation;  this,  in  cold weather, requires se-
 veral days, but in summer it takes  place  in a few hours.
 Sometimes it suddenly becomes sour in consequence  of
 changes in the atmosphere,  as in stormy times.   But this
 may in a  great measure be prevented by previously boiling
 the milk.   It is stated, that if to  a quart bottle  of milk
one or two table spoons of  ardent spirit be added,  and the
 bottle be  corked tight, but opened occasionally to let out
 the airs that are  formed, then,  in the course of two or 
DISCOURSE XIV.              411
three weeks,  it will be converted  into a  most excellent
vinegar.

   If fresh milk be put into a moderately warm place, and
be often stirred to  prevent  the  separation of its parts, it
undergoes   the  vinous  fermentation.    This  process is
quickened  by the addition of a fermenting  body, and on
distillation  a strong  spirit may be obtained.   The Tartars,
and some Russians, are in the habit of drinking a liquor
prepared from the milk of  their mares, and sometimes from
that of  their cows.  It is stated,  that for this purpose,  the
milk pure and fresh, should be put in a vessel with a small
neck, to which some fermenting  fluid is added,  and then it
should be two or three times a day agitated for  the extrica-
tion of  the airs, during four or five weeks.   On keeping it
afterwards in vessels tightly stopped for two or three weeks
its quality  is much improved,  and  on  distillation  it will
yield ardent spirit.  Human milk, we  are  informed, will
yield the most of  this spirit.

   Milk, when procured from cows directly  after calving,
is called beastings.    It is of a yellow color, sometimes mix-
ed with streaks of blood; it is  thick and clammy, but its
taste is like other  milk.  It is more difficult to coagulate it
than other milk.   After several days, the milk  becomes of
its usual appearance; however,   the quantity  of curd it
yields generally increases with the time after delivery.   The
quantity  of milk given by cows is  always lessened when
the diet of the cow is changed,  and the original quantity
is not  given, until the animal becomes accustomed to the
new food.   The quantity of mUk is also  increased when
the  animal is accustomed  to fluid food ;  but its  quality is
rather  lessened.   The peculiar properties of the food  also
 have great influence  on the milk.   Every one  knows that
 onions, garlic, clover, &c give the milk  particular disa- 
412
DISCOURSE  XIV.
greeable  flavors, while  the  nutritious vegetables, as corn,
and  other  seed,  as certainly render  it more  agreeable.
Hence, milk in the autumn is more agreeable  and richer
than in  the spring.    The richness of  milk  is  usu-
ally judged of by the quantity of cream it yields ; and the
cream  which first rises contains more butter than that which
follows.  Dr. Anderson states, that the quantity of cream
collected from the milk of the cow, is different according to
the time of its being drawn, and that the small quantity of
milk, which comes the last, contains  about  sixteen times
more cream than the same quantity drawn first  at the same
milking.  The cream  obtained  from  the last milk is  also
much  richer, and of a deep orange  color, while  that of
the other is white.  "  From experiments it appears," says
Dr.  Anderson, " that a person who, by bad milking of his
cow loses but half a pint of his milk, loses in fact about
as much cream as would be afforded by six or  eight pints
at the  beginning;  and loses besides that  part of the cream
which alone can give richness and high flavor to butter."

   With respect to the separation of cream from the milk,
it appears to take  place with the greatest regularity,  in a
temperature of from 50° to 55°, and when the heat  ex-
ceeds 65°,  the milk soOn coagulates,  and  yields but little
cream.  The quantity of cream is also lessened if the milk
be agitated; but it is increased, if  allowed to rest in large
open vessels with a wide surface exposed.  It is supposed,
that in this case the cream acquires consistence from  the
absorption of oxigen from the air.

   Butter.   This is obtained as every one knows by churn-
ing  the cream or nv'l'k of the cow.   Butter  is  in  general
of a yellow color, but sometimes it is as white as fat, and
of an  inferior quality.   The color,  however, depends very
much  on  the state or  constitution  of  the animal', yet 
DISCOURSE  XIV.
413
the food has no doubt some influence.   The contact of the
air has likewise an effect in coloring it,  for in some instan-
ces,  that which is  quite white, acquires a yellow color a
certain time after  its preparation, and on being cut, ap-
pears less yellow internally.

   But the quantity and agreeable  flavor of  butter is of
much  more consequence than its color.  In order to ex-
tract in largest quantities, some management is necessary.

   According  to Mr. Robinson, butter from cream is much
richer than that from milk, but  it is less  in quantity, and
does not keep so long sweet.  Doctor  Anderson states that
if the cream  be got  from milk, exposed to too low a tem-
perature,  the  butter  when  extracted  will be pale; very
small in quantity; of little taste; very hard, and of no
value.  Butter likewise,  when extracted from  new cream,
tastes more agreeable than when extracted from old: for,
to make  butter of the best quality, it will not only be ne-
cessary to separate the  first drawn milk from  the rest, but
likewise to take only the cream that is separated  from the
best milk, as  it is only the  first rising cream, that is of the
best quality.  Thus the richness of the highland butter is
attributed by  Dr. Anderson to the  practice of giving the
first drawn milk to the calves, and keeping the rest for the
dairy ; and the quality  and richness of the butter will  be
improved in proportion  to the smallness of the quantity  of
 the last drawn milk. Another circumstance, in the separa-
tion of butter from cream,  is, that it does not take place
till after the last has become sour;  if,  therefore,  it be agi-
tated before that acidity  has  begun no  butter can be obtain-
 ed, and the agitation must be continued until that sourness
 be produced,  after which the butter begins to form. Hence,
 the cream ought  to remain in  the  vessel appropriated for
 keeping it, until it has  acquired  that proper degree of aei- 
*1*               DISCOURSE  XIV.
diiyby which butter is easily extracted by a moderate de-
gree of agitation; and only by this process can  very  fine
butter be obtained.   In summer,  while the temperature is
warm, if the agitation be continued until  the acidity is pro-
duced, the process  of churning will be-long and tedious,
and the butter of a soft consistence ; and in winter the dis-
advantages  are greater.   Cream, therefore, which has been
kept three or four days in  summer, is in an excellent condition
for producing butter.   And Dr. Anderson states that from
three to seven days,  in general, will  be found the  most pro-
per time for keeping cream before it is churned.  Mr. Four-
croy states  that a quantity of oxigen is. in this time  absorb-
ed by the cream,  which is the cause of. its superiority over
that which is fresh; and  it is also very probable that oxigen
is absorbed during the churning.   It is certain that a quan-
tity of carbonic acid air is extricated during this process.

   Doctor Anderson states that in the western part of Eng-
land the best butter is made as follows :  the milk is first de-
posited  in  earthen pans, where it remains twelve hours in
summer and  twenty-four in winter ;  they are then  remov-
ed to  stoves,  heated  for that purpose  with  hot embers;
here  they  remain till bubbles arise, and  the cream changes
its color:  this is  called  scalded cream.  It is then removed
with care to the dairy where it remains twelve hours longer,
when it is  skimmed and  the cream is churned. This, when
deprived of its salt by washing,  is said to be equal to the
best tresh butter.

   For those who wish to make most butter from their milk,
it would not be adviseable to separate their cream from their
milk.   From experiments I have repeatedly seen made on
my father's farm, it is unquestionably most advantageous to
allow the milk to be converted into clabber, or to be coagu* 
DISCOURSE  XIV.
4lS
lated, and then to churn it with the cream.  The quantity of
butter yielded by so doing, is invariably greater, and the fa-
mily think of  better quality, than  that  yielded by other
means;  and the  buttermilk is also  found uncommonly
good.

  Butter,  when melted,  has  its  properties  materially
changed: Its color, taste  and texture  become  altered.   It
is  partly transparent, and appears in  the form of grains;
its taste is insipid,  and similar to that of fat.   These chan-
ges which  butter undergoes  by melting, are  caused by the
separation  of some mucilage and its  curd,  to  which the
butter owes its agreeable qualities.

   Common butter, it is well known, is very apt to lose  its
delicate  flavor, and  acquire a strong disagreeable  sharp
taste,  commonly called  rancidity.    It appears  to  be
more susceptible  of this  change,  than  other  oily  mat-
ters.   This rancidity arises, it appears, from  the same cause
as that  of other oils; viz. from the absorption of  oxigen
from the air by a mucilage.   And the  way  to lessen  its
tendency to become rancid, is to lessen the quantity of this
mucilage,  and prevent the contact of  oxigen.   The muci-
lage is deposited by melting the butter; but  this method is
not practised, in consequence of its depriving  the butter of
its agreeable taste.   Much of the mucilage,  however, may
be extracted by repeatedly washing  the butter,  particularly
in warm water; and the butter so  served, is  found to re-
 main  under common circumstances  a great  while longer
 without becoming rancid, than common  butter.  The ten-
 dency to rancidity is also lessened, by  keeping the butter in
 a cold place.

    In order to preserve butter more  effectually from becom-
 ing rancid than common salt can, the  following method has 
416
DISCOURSE XIV.
been very strongly recommended.  Take one part of sugar,
one of saltpetre, and two of the best common salt, and rub
them up together very finely.   One ounce of  this is to be
mixed with a pound of butter, as soon as it is freed from
the buttermilk by washing.  It is then  to be put in a close
and dry vessel,  from which the air is to be excluded; and it
will remain pure for many years.

  Buttermilk.   This is almost uniformly found to retain a
portion of butter, diffused in  small lumps.  In most of its
properties, it bears a very striking resemblance to skimmed
milk.  It is however of a  white color; is  more palatable,
and is consequently very generally used, particularly by the
servants of the southern states, as an article of diet.

   Cheese.  This is an  article known many hundred years4
ago : as before observed,  it is prepared from the curd of
milk.   It is valuable in  proportion  to the  quantity of
cream it contains.  It is well known to cheese  makers,  that
the excellence of cheese depends in a great measure on the
manner of separating  the whey from the curd.  If the milk
be much heated, the  coagulum broken in pieces,  and the
whey forcibly pressed out, the cheese is scarce good for
any thing;  but the whey is delicious, especially that last
squeezed out, and butter  may be obtained from it in con-
siderable quantity, which  shows that the cream was separa-
ted with the whey.  Whereas,  if the milk to  be made into
cheese be not much heated (a temperature of  100°  is suffi-
cient) ;  if the coagulum  be allowed to  remain unbroken
and the whey be separated by very slow  and  gentle pres-
sure, the cheese is excellent,  but the whey is  nearly color-
less, and contains no  cream.  Cheese  so made melts at a
moderate heat  in consequence  of its  oil, which gives it
flavor and smell. But bad cheese when heated, dries, curls
and exhibits the appearance of burning horn. 
DISCOURSE  XIV.
417
  Cow's milk  is not the only  milk employed in making
cheese.  The milk of the goat  is very  frequently used for
the purpose; as the cheese made from  it is very rich mar-
rowy, melting,  and  of an agreeable taste.   The  milk of
sheep is also employed in  some  parts for making cheese.
The famous Roquefort cheese is made by a mixture  of goats
and sheep's milk. It must readily appear that a great variety
of flavored cheeses may be  made, by mixing in various pro-
portions, the milk and cream of different animals; and then
a good  deal depends on the particular  manner of making
and preserving it.  It is always adviseable to keep cheese in
cold places and properly salted.

  The  article used for the coagulation  of milk  is called
rennet, which  is  the  fourth  stomach of calves.   This is
usually  dried and preserved for use.  It operates by virtue
of a secretion it contains,  called the gastric juice,  which is
formed  in the stomach of  all animals.   Hence, we find
the milk vomited by children, is usually coagulated in con-
sequence of the gastric juice of  their stomachs.  When the
rennet is added to milk,  or cream heated to 100° as above,
it requires from one fourth to  half an hour for its gastric
juice to be  dissolved to coagulate milk.

   It may not be amiss to add the following receipt for.
making Stilton ctyese, which is taken from the newspapers,

   « Take the night's cream, and put  it to  the morning's
new milk,  with the rennet; when the  curd is formed, it is
not to be broken, as is done with other cheese, but take it
out with a soil dish altogether,  and place  it in a  sieve to
drain gradually, and as it drains, keep gradually pressing it,
till it becomes firm  and dry,  then place  it in a  wooden
hoop ; afterwards it is to be kept dry on boards, turned fre- 
418
DISCOURSE XIV.
quendy with  cloth  binders round it,  which  are  to  be
lightened as occasion requires.   It is customary after these
cheeses become  sufficiently firm, to rub them every day,
particularly in moist weather with a dry cloth."
  THE  milk of all other animals consist nearly of the
same  ingredients as cows' milk; but there is  a great dif-
ference in the proportions of these ingredients,  as will ap-
pear from the following :

   Woman's milk has a much sweeter taste than cow's milk.
When allowed to remain at rest  for a  sufficient time,  a
cream gathers on its surface.  This cream is more abundant
than in cow's milk, and its color is usually much whiter.
After it  is separated, the milk is exceedingly thin, and has
more the appearance of whey,  with a blueish  white  color,
than  of  skimmed milk.   The  methods by  which  cow's
milk  is coagulated, do not succeed in coagulating women's
milk.    However,  their  milk  contains  curd,  for if it  be
boiled the curd rises on the surface.  Its not  coagulating,
is attributed to the great quantity of water it contains.

   Though the cream of this  milk be churned ever so long
no butter can be obtained from it; but if after being agitated
for some hours,  it  be  allowed to  remain at rest  for a day
or two, it separates into two parts; a  fluid which occupies
the lower part of the vessel, which is colorless like  water;
and a thick white oily fluid,  which swims on  the surface.
The  lower  fluid contains sugar of milk, and some curd,
the upper one does not differ from cream, except in con-
sistence.  The oily part of this  cream  then, cannot be se- 
DISCOURSE  XIV.
419
parated from its curd: and  this cream contains a greater
portion of curd than the cream of  cow's milk.

   When this milk, after the curd  is  separated from  it, is
slowly evaporated, it yields crystals of the sugar of milk
and  common  salt.   The  quantity  is  rather greater than
that  afforded by cow's milk.

   Thus it  appears that woman's milk differs from that of
cow's in three particulars.

   1.  It contains a much smaller quantity of curd.

   2.  Its oil is so intimately  combined with its curd,  that i$
does not yield butter.

   3.  It contains rather more sugar of  milk.

   It should be observed that the  quantity of curd in wo-
man's milk  increases in proportion to the time after deli-
very; and nearly the same has been observed with respect
to cow's milk.

   Ass^s  milk, has a very strong  resemblance to human
milk;  it has nearly the same color,  smell and consistence.
When left at rest for  a sufficient time, a cream forms  upon
its surface, but not  in such abundance as upon  woman's
milk.  This cream  by very long agitation yields  a  butter
which is always soft, white, and tasteless;  and what is sin-
gular, very readily mixes  again with the buttermilk; but it
may be again separated by agitation, if the vessel contain-
ing it  be kept cold.  This milk when skimmed, is thin,
and  has an  agreeable sweetish taste.  Ardent spirit and
acids separate from it a little curd,  the consistence of which
is considerable.  The serum yields a sugar of milk, and
muriate of lime by evaporation. 
420              DISCOURSE XIV.
  Ass's milk,  therefore, differs from cow's milk in three
particulars :

   1.  Its cream is less abundant and more insipid.

   2.  It contains less curd.

   3.  It contains more sugar of milk.

   Goafs milk,  if we except its consistence, which is greater,
 does  not  differ much from cow's milk.   Like that milk, it
 throws up abundance of cream, from which butter is easily
 extracted.  This milk, when skimmed, coagulates j ust as
 cow's, and yields a greater quantity of curd.  Its whey con-
 tains sugar of milk, muriate of  lime, and common  salt.

   Ewe's milk resembles  very strikingly that of the cow.
 Its cream  is  rather mpre abundant,  and yields a  butter,
 which, however, never acquires the consistence of cow's
 milk.  Its curd  has a fatty appearance, and may be readily
 made to  assume the consistence of the curd of  cow's milk.
 It makes very valuable cheese.

    Mare's milk, is thinner than that of the cow, but not so
 thin as woman's milk.  Its  cream cannot be converted into
 butter by agitation.  The  skimmed milk  coagulates  pre-
 cisely as cow's  milk, but the  curd is not so abundant.—
 The serum contains sugar of milk, sulphate of lime, and
 muriate  of lime.


                        OF BILE.

    BILE is a  liquid which is formed in the liver, of a yel-
  lowish green color, an oily feel, bitter taste, and peculiar 
DISCOURSE  XIV.              4«1
smell.   In most animals,  considerable quantities of it  are
usually found collected  in the gall bladder, and it is com-
monly called gall.

   When strongly agitated, bile lathers like soap and assumes
a yellow color;  but it will not unite  with oils.  However,
it dissolves a portion of soap readily, and is often employed
to  free  cloth  from  greasy spots.   When  four  parts of
vinegar and five of bile  are  mixed together, the mixture
has a sweet taste and does not coagulate  milk.  The  acid
of milk has precisely the same  effect as  vinegar.  If bile
be heated,  and slightly evaporated,  it may  be  kept  for
many months without putrefying.

    A great number of experiments  have  been made with
 bile; but they are not of much consequence.  They were
 performed  with a view to throw light  on the treatment
 of the diseases which are called biliary.   But they have
 not thrown any light whatever on the subject.  They  have
 established the fact,however,that it is a very compound fluid,
 and generally contains a portion of the following substances:
  1  water, 2  resin, 3 albumen,  4 soda,  S  sulphurated hi-
  drogen, 6 a sweet salt, 7  common salt, 8 phosphate of lime.

    It is  wordiy  of being recorded, that Mr. Fourcroy, a
  French chemist, has been able to procure bile from the blood
  of an ox. He did it simply by coagulating blood, by boiling
  it in distilled water; and  then filtering it and evaporating the
  fluid.   The fluid which is obtained is of a green color; and
  when evaporated to the consistence of honey, it was precise-
  ly like bile.

    Most of the  acids when added to bile,  render it  of a
  deep green color.  It is to this cause, that the bile vomited
  up  from the  stomachs  of patients, is  so generally  of a 
422
DISCOURSE XIV.
green color; the color being given by the acids found in the
stomach.

  The uses of bile  are  not exactly known.   Many have
supposed that it is an excretion designed merely to free the
system from an injurious fluid: but with greater probability
it is stated to serve as a stimulus to the intestines,  to keep
up their motion.  Hence in doses of one or two ounces,  it
is generally given to excite purging.   However, nothing  is
more certain, than that the common  notions about bile's
being the cause of fevers, are unfounded and absurd.  In
the first  place, but a small quantity of it  can remain  at
once in the stomach  and bowels: and the large quantites
which are evacuated when an emetic is taken,  are brought
out of the gail bladder at the time of vomiting, in  conse-
quence  of the  convulsive motion  of the  stomach.   It  is
this motion of the  stomach, which proves of service to
patients  laboring under supposed biliary  fevers,  and not
the evacuation of a little bile.
OF THE GASTRIC JUICE.
  THIS is a fluid found in the stomach of all animals ; it is
secreted by small vessels  which  line the  inner coat of the
stomach.  When food is taken into the stomach,  this juice
acts upon and dissolves it, and in consequence adapts it for
entering into the general circulating mass.   It is to b*con-
sidered as a solvend for the food of animals.

  The properties of the gastric juice are  found very much
to vary with the diet of animals.  In all animals it dissolves 
DISCOURSE  XIV.
423
the particular food to which the animal is accustomed; but
it does not act on that to which the stomach is not habituated.
In consequence of this, the gastric juice of an animal living
on meat, will not dissolve a vegetable substance;  nor will
ffoat of an animal living on vegetables  act on meat.   Hence
the stomachs of eagles, or any other  carnivorous  animals,
will not digest vegetables;  nor will the stomachs of sheep,
horses or any other herbivorous animals digest flesh. How-
ever,  on accustoming the  stomachs of these animals to
any kind of food, in time,  they will be brought to digest it
completely; so  that  such  is the nature of the stomach,
that it varies its secretions, and secretes a proper menstruum
for the food applied to it.   Hence horses, cows, sheep, &c.
may be made to live on flesh; and  eagles,  &c. to  live on
vegetables.

   Although  the gastric juice of animals varies  with the
diet of  the animal, yet it is possessed  of general properties,
by which it may be  distinguished.   It resists putrefaction
in  a great degree.  Hence, on introducing  putrid flesh, &c.
in  the stomachs of animals, it is frequently rendered per-
fectly pure.  It curdles or coagulates milk.  Hence the
reason that children frequently throw up curd after sucking
their mother; hence  the rennet or fourth stomach of calves
is  used to convert milk into clabber.   The gastric juice or
the rennet is dried,  and then dissolves in the milk to  coag-
 ulate it.  Would it not be well, instead of preserving the
 stomach's of calves to make cheese,  to procure  the juice
 from the stomach's of animals,  and evaporate it in the sun
 to dryness, and use it as occasion requires ?

    The gastric  juice of animals,  frequently contains an
 acid, which has been generally found to be the  phosphoric
 acid.   This acid, however, is not, as has been supposed,
 the cause of its coagulating milk.  Some times the contents 
424
DISCOURSE XIV.
of the stomach undergo an acetous fermentation, and then
different acids are produced.  At other times,  in cases of ,
disorders of the stomach, the gastric liquor is found to be
of an alkaline nature.

  The importance of this  fluid in animals  must appear
very considerable.  Besides its use in the animals in which
it is formed, it has been recommended as a medicine, when
taken from their stomachs.   To old  ulcers, it has been
applied with great success,  and it has been successfully ex-
hibited to patients laboring under  debility and indigestion.
On this subject,  it may not be amiss to extract the follow-
ing from my Thesis.  " The difficulty  of procuring the
gastric juice, may prevent its introduction into general use;
but if  in a few cases  it affords relief,  it is entitled to a
place in the Materia Medica.  This objection, however,
cannot be urged against our using it in a manner, and for a
purpose I will now propose."

   " It is well known that there are medicines (resins, for ex-
ample) which are soluble  in the  gastric juice only when
blended with gum or mucus.   This appears the reason why
aloes will act only in the rectum,  where it can unite to the
mucus of the gut.  It must appear very evident, that most
medicines do not act on the stomach before they are dissolved
in its juice or menstruum:  Nor can it  be  doubted, that
the  effects  of  medicine vary with their  solvent or men-
struum.   Now as the gastric juice is liable to  the  greatest
changes, we frequently see  the same medicine producing
different effects on different persons; and it  must be also
on this account, that the same medicine produces different
effects at different times  on the same person, and that  in
other  instances, only particular forms of a medicine will
produce  an effect.  Dr. Rush in speaking of clinical cases,
observed that opium in substance, in a  pill  he had found 
DISCOURSE  XIV.
425
to check  vomiting,  when no  other of  its  preparations
would.   And in the case of my dear mother, lately affected
with an incessant vomiting, I found that only a watery so-
lution  of opium  would yield relief.  Authors have obser-
ved in  some  instances, that very active  medicines would
prove either inert, or exert some uncommon power on the
system.  To prevent such occurrences,  I imagine it is only
necessary  to mix  the doses with a small quantity of the
gastric juice of healthy carnivorous animals.  This would
be the  more  proper in  dangerous cases, where  at critical
periods, a  slight  irregularity might prove destructive.—
This suggestion appears  so plausible, that I  cannot avoid
wishing, that practitioners will at  least ascertain if it de-
serve to be prosecuted."
OF URINE.
  NO animal substance has attracted more attention than
urine,  both on account of  its  supposed connexion with
diseases, and on  account  of the very  singular products
which have been obtained from it.  When fresh, it  differs
considerably in its appearance, this depending on the state
of the person,  and the time at which it is voided.   In ge-
neral,  healthy urine is a transparent liquid, of a fight amber
color,  an aromatic odour, resembling that of violets, and
a disagreeable bitter taste.   When'it cools, its strong odour
leaves it, and  it is succeeded by another, well known by
the name of urinous smell.  This smell is succeeded by that
of another, resembling sour  milk, which in its turn gives
wav to an alkalescent and fetid odour.
   ;                       3H 
126
DISCOURSE  XIV.
  If urine be evaporated by a slow fire, to the consistence
of a thick syrup,  it assumes a deep brown color,  and ex-
hales a fetid ammoniacal odour.   When allowed to cool, it
concretes  into a mass.  If four times the weight of ardent
spirit be poured on this mass, at intervals,  and a slight heat
be applied, the greatest part is dissolved.   The spirit ap-
pears of  a brown color ;  it should be poured off,  and dis-
tilled in a retort till the mixture  has boiled for some time,
and acquired the consistence of  syrup.   By this  time the
whole of  the spirit has passed off, and'die matter  on cool-
ing concretes.  This substance is called urea, which com-
poses nineteen twentieths of the  urine, provided the watery
part be excluded.   To this substance, the taste and smell
of urine  are owing; and in fact most of the characteristics
of urine  depend on it.

   The quantity of  urea  varies considerably in  different
 urines.   In the urine voided soon after eating and drinking,
 very little of it is found, and still less in that which is voided
 during fits of the hystericks.

    A number of  experiments have been made,  to  ascertain
 exactly the constituents  of urine.   It is too uninteresting
 and useless to detail those  experiments ; however, it  may
 not be amiss to notice the different substances, which have
 been found  in it.  They are upwards of eighteen, to wit:
 water, phosphoric acid,  phosphate  of lime, phosphate of
 magnesia,  carbonic acid,  carbonate  of  lime, uric acid,
 rosaic  acid, benzoic acid,  gelatine, albumen, urea,  phos-
 phate of  soda, phosphate of ammonia, muriate of ammo-
 nia, muriate of soda, and sulphur.

   No doubt, most  of these substances which  have been
 found in  urine,  are formed during the decomposition of it
 by art.  Occasionally other compounds are also found in it; 
                  DISCOURSE XIV.              427

such  as  the urate of soda, sulphate of soda,  muriate  of
potash, &c.  No substance putrefies sooner, or  exhales  a
more detestable odour during its decomposition, than this
secretion ; but there  is a material difference in the time in
which this takes place in different urines.   In some putre-
faction takes place almost as soon as it is voided; whereas
several days pass off before  it  takes  place in other  urine.
This difference is found to depend on the quantity of gela-
tine and  albumen  which urine contains.   When there  is
very little of these ^substances present, urine remains a long
time unchanged; on the contrary, the greater the quantity of
gelatine and albumen, the sooner dpes  putrefaction com-
mence.   The  putrefaction  of one's urine is,  therefore,
in some degree,  the test  of  the  health  of  the person
who has voided it: for according to Fourcroy,  an  abundance
of gelatine in  urine,  indicates some defect in  the  diges-
tive power.   The presence of the gelatine may be detected
by the addition of a solution of tannin to the urine.

  Human  urine is  remarkably  subject to  alterations by
disease :  and the  changes to  which  it is liable have long
attracted the attention of physicians, as in  some measure,
they serve to indicate  the state of patients, and the progress
of the disease under which they labor.  The following are
the most remarkable of these changes that have been ob-
served ;

   1. In inflammatory diseases, the urine is of a red color,
and is very acrid; it does not deposit any thing on standing.

  2.  During jaundice,  the urine  has an orange yellow
color,  and communicates the same tint to linen.   Muriatic
acid renders this urine a little green, and thus detects the
presence of bile. 
428              DISCOURSE XIV.
  3. On the termination of  inflammatory diseases,  the
urine becomes abundant, and deposits  copiously  a  pink
colored sediment.

  4. During fits of the hystericks, the urine usually  flows
abundantly.  It is limpid and colorless,  containing much
salt, but little urea  and gelatine.

  5.  The  urine of gouty  people,  contains much  less  of
the phosphoric acid than healthy urine.

  6. In general dropsy, the urine is loaded with albumen
and becomes milky,%or even coagulates when heated,  or at
least when  acids are mixed with it.   In  dropsy  from dis-
eased  liver, no albumen  is  present; the urine is  scanty*
high colored,  and deposits the pink colored sediment.

   7. In indigestion, the urine contains much gelatine* and
 yields a copious precipitate with tannin.

   8. The  urine of  patients laboring under rickets is loaded
with the phosphate of  lime.

   9.  In the disease called diabetes, the urine is sweet tasted,
and of course contains sugar.  According to  Cruickshank,
 the urine voided daily by a  diabetic patient,  contained 29
ounces of  sugar.

   But our knowledge  concerning the diseases  indicated by
the appearance of urine, is very defective,  and nothing is
more certain,  than that the number of p—s Doctors, who
pretend to prescribe medicines from the appearance of the
urine, are vile impostors, although  some of them have acci-
dentally acquired in different parts of the country considet-
able reputation 
DISCOURSE XIV.              429
                   THE URINE

Of the  horse is found  to  differ  somewhat  from that of
man,   It has a peculiar  odour after  exercise, it is emit-
ted, thick and  milky;  at  other times, it is transparent,
but becomes muddy soon after emission.  When exposed
to the air, its surface becomes covered with a crust of chalk.
It gives a green color to syrup of violets, and has the con-
sistence of mucilage.  It does not contain much urea, or any
phosphorus, according to the experiments of  Fourcroy.

   The urine of the cow resembles that of the horse; but
nothing is  known of  it, or of any of the other urines
which have been examined worth particular  attention.

   The urine  of animals, from the salts it contains,  must
readily appear to  be capable of acting as a  manure.   It is
used in the preparation of some dyes;  and  sometimes for
the purpose of preparing phosphorus.
OF POISONOUS  SECRETIONS.
  SERPENTS, bees, scorpions, spiders,  and several other
animals are furnished with  juices of a poisonous  nature,
which when poured into fresh Wounds, occasion the disease
or death of the wounded animal.  From the small quantities
in which these have been procured, their chemical  proper-
ties have been but imperfectly examined.   The following
is the  chief of  what has  been advanced  on the subject—
A more particular account will be found in a most valuable 
430
DISCOURSE XIV.
 paper, published in vol. iii. of  the American Translations.
 by the indefatigable Professor, Dr. Barton of Philadelphia.

   The poison of the viper is a yellow liquid, which is found
 in two small vessels in the animals mouth.  These commu-
 nicate by a tube with the crooked fangs, which are hollow,
 and terminate in  a small cavity.  When the animal bites,
 the vessels are squeezed, and the poison is forced through the
 fangs into the woufid, where it produces the fatal effects of
 the viper's bite.  Hence, if the vessels be extracted, or the li-
 quid prevented  from flowing into the wound, the  bite is
 harmless; and if applied to wounds of the body, made  with
 sharp instruments, it operates  as powerfully,  as  when in-
 troduced by the viper itself.  When applied to the tongue,
 this  poison occasions a sense of numbness.   It has the ap-
 pearance of oil before the microscope, but it readily unites
 with water.   When exposed  to the  open  air, the watery
 part gradually evaporates, and a substance remains resem-
 bling gum arabic;  and it is very soluble in  water, but not
 in alcohol.   It is precipitated from its  solution in water,
 by the addition of ardent  spirit, in the  form of a white
 powder.   Neither  acids   or  alkalies  have much effect
 upon it.

   For a long time it was thought that ammonia  or the vola-
 tile alkali was an antidote to the bite of the  viper.  It  was
 applied, in consequence of  the  supposition that the poison
 was  an  acid, and  that the  alkali  would combine with it.
 Fontaua, however, found that it did not destroy the poison
 when mixt with it.  Notwithstanding this, Dr. Ramsay has
 recommended it as  a certain cure for the bite of the rattle
 snake.

  The venom of the bee and wasp, is also  a liquid, con-
tained in a small vessel forced through the hollow tube of  the 
DISCOURSE  XIV.
431
sting into the wound inflicted by it.  It is stated to resemble
that of the viper ;  but to be much longer in drying.  The
poison of  the  scorpion resembles that of the viper also;
but its taste is hot and acrid as that of the venom of bees
and wasps.  No experiments have been made of the poison
of spiders. But from the rapidity with which these animals
destroy their prey, and one another, it must be very strong.



                     OF SALIVA.
  THIS is the fluid secreted in the mouth, and commonly
called spittle.   It is nearly as limpid as water, but is much
more thick or viscid.  It has neither taste or smell.  When
agitated, it froths like  other adhesive fluids, and in fact,
it is usually frothy in consequence of its mixture with air.

  Saliva does not  mix with oil: If rubbed up in a mortar
with  water they  combine together pretty well.   It has a
great affinity for oxigen, absorbs it readily from the air, and
gives it  out, again  to  other bodies.   Hence the reason
why gold or silver,  rubbed up in  a  mortar with  saliva  is
oxided :  and why the mixture of mercury with oils is expe-
dited by spitting  in the mixture, as  is often done  by  those
making mercurial ointment: It is probable that it is on this
account, that spittle is an useful application to sores of the
skin ; and that dogs and other animals have constantly re-
course to this  remedy for their ulcers.

   Saliva when boiled in water, gives up a small quantity
of albumen.  When evaporated, it yields  small crystals  of
common salt; and upwards of eighty parts of it, are found to 
/
 432              DISCOURSE XIV.

be common water. According to the most accurate statement,
the following substances exist in saliva:  1 mucilage, 2 albu-
men, 3 common  salt, 4 phosphate  of soda, 5 phosphate
of lime,  6 phosphate of ammonia.

  But it cannot be doubted, that like the other animal fluids,
saliva is liable to many changes from diseases and variations
of habit.

  The  concretions which are sometimes  formed in  the
mouth,  and particularly  the tartar or bony crust, which so
often attaches  itself to the teeth, are chiefly composed of
the phosphate  of lime.

  Besides the secretions we have considered, several other-s
have been examined by chemists; but as nothing worthy
of particular attention has been noticed,  it will be useless
to dwell on them.
A*
tasa&sas 
DISCOURSE  XV.
   THERE are but few subjects which have excited more
attention than the means by which animal parts are formed.

   The nutrientia, or substances which enter into the compo-
sition, or which nourish animals, are universally known to be
chiefly derived from  the  vegetable and animal kingdoms.
Excepting the air and  water,  no other substances afford
a support.  The greatest quantity of nourishment is un-
questionably derived from a given bulk  of  animal  matter,
when circumstances are the same, as the experience of eve-
ry attentive observer will  shew.  It will also appear, that
of animal substances, fat, blood, milk, flesh and soft bones
are most  nutrious.  Hence  the great vigor of  animals
accustomed to eating such food.

   Of the vegetable substances yielding a support, the most
remarkable are the following:
                         3 I
 
434
DISCOURSE  XV.
  Sugar.  This is universally known not only to be a very
palatable,  but a very nourishing article of diet.  The ne-
groes of the West  Indies, annually grow fat while  press-
ing the cane, in  consequence of eating it in considerable
quantities at that  time.   A variety of vegetable sweet sub-
stances owe their very nutricious qualities in great measure
to the sugar they contain.  Hence it is a proper article for
children, and is invariably found in the milk which they suck.

  Fecula or starch.    This is also very nutricious.   As be-
fore remarked it exists in many grains and roots, and ren-
ders them  nourishing; as instanced in wheat, rye, bar-
ley, potatoes,  &c.

   Gluten, commonly is found in combination with fecula,
particularly in nutricious grains, and no doubt adds to their
qualities.

   Gum.  This is unquestionably to be ranked among the
very nourishing vegetable bodies. The lives of people have
been saved by eating gum arabic, when no other substance
could be had.  And perhaps it would be  advantageous  to
make a greater use  of the gummy or mucilaginous seeds in
our diet  The quince, flax, and water mellon seeds,  appear
to be particularly well adapted for food.

   Oil.  This is not less  remarkable than the other  sub-
stances we have named for yielding nourishment to animals.
The olive oil of commerce is generally used, and particularly
by the Turks, as  an article of  diet.

   Acids, obtained  from the  vegetable kingdom,  are  also
nourishing, particularly when  in  combination with other
bodies; as with sugar in conserves, &c.  It is, however, not
known what are precisely their nutricious qualities.   When 
DISCOURSE  XV.               435
uncombined,  as in vinegar and lemon juice, and long used,
they have been known to produce  considerable  disease in
the stomachs of persons.

  Besides the above  substances, it is probable that some
others, particularly those formed of carbon, nitrogen, ox-
igen and hidrogen, yield a support at least to some animals.
Perhaps, also, the bodies containing  acrid substances, as
pepper, mustard, &c. may contribute towards nourishing
the human race,  as well as other animals; such are, how-
ever,  chiefly  used as condiments.  In  general,  however,
the nourishing  qualities  of an  article to be used as food,
may be judged of correctly by  ascertaining the quantity of
the proximate  principles of vegetables contained 'in it,
which were first named.

   But the nourishing qualities  of substances are found to
depend very  much on the habits of the animal.   Before
the articles combine with the animal bodies, they must re-
main some time in the stomach, and there be dissolved in
the gastric juice, as observed while considering this seCretion.
It  must be remembered,  that the  power  of the  gastric
juice to act on the bodies taken in the stomach, depends
greatly on the  food  to which the animal is  accustomed.
Hence, flesh will not shortly  be digested by  those accus-
tomed to live on vegetables.   Hence, when the stomach is
diseased we find that bodies remain in it a long time, in
 some instances, without undergoing any change.   Hence,
 in judging of  the wholesome  qualities of food, we must
 learn first  the habits of the person.   Hence the error of
 those,  who on  eating food, and  vomiting it  unchanged a
 day after, on being taken sick attribute their sickness to the
 food, forgetting (as I have known a physician  of some note
 to do) that it was owing to the previous disease  of the sto-
 mach, that the article was not acted on by the juice of the 
436
DISCOURSE  XV.
stomach.   Hence,  those who change their diet should do
it very cautiously  and gradually,  lest they disorder  their
stomachs.

  The food,  when dissolved  in  the gastric juice, passes
down through the  bowels, which are lined with innumer-
able and small vessels. These small vessels absorb the greater
part of it. No sooner is it absorbed, than it is converted into
a white milky looking substance called chyle.  This chyle is
then  conveyed  by a large vessel which empties into one  of
the veins containing blood: here it mixes with the blood, and
with it,is conveyed to the lungs; in which place it is convert-
ed into blood of a very red color,  and distinguished by the
name of arterial blood.   This arterial blood, in consequence
of the action of the heart and arteries, (which depends on
the contraction  of  fibres,) is conveyed all over the body;
where in some parts,  it is converted into fibres, or a part
of the living animal body; in other parts, it is changed in-
to the fluids  called secretions, as milk, urine,  perspiration,
fat,  &c.  And  the last  part returns through very small
tubes, which unite and form veins.  This blood is then of
a dark color, and is known by the term venous blood.   The
veins  convey it to the lungs, where again it is converted
into arterial blood, and is as above  circulated through the
body ;  constantly diminishing in  quantity, and constantly
supplied again from the food that is taken.

   The blood of  the veins unquestionably is in the lungs con-
verted into red arterial blood,in consequence of the influence
of the air we breathe, and the oxigen of this air: for whenever
this oxigen air is withheld, the blood is unchanged, and the
animal soon loses its heat and expires. Besides this, however,
in the lungs, the blood gives out carbonic acid and moisture.
Hence it is always found, that the oxigen of air which is
breathed, is diminishing in quantity.  It seems  then that the 
DISCOURSE  XV.
437
lungs of animals are chiefly useful in consequence of their be-
ing so made or constructed, that the venous blood in them at-
tracts the oxigen from the air which is applied to them; and
that this oxigen converts the blood  into red arterial blood,
which is alone capable of answering the purposes of the body.
The oxigen,  however,  in uniting to the blood in the lungs
does not lose all its latent heat; for when the blood is convey-
ed to other parts, as to the extremities, it there loses its capa-
city  to retain its latent heat, which consequently escapes in
the form of  sensible heat, and so causes the warmth which
distinguishes most animal parts.   Hence the heat of animals
is found proportionate  to the quantity of air they breathe.
Hence  the  necessity of fresh air for the  preservation of
animal  life and  animal heat; and also  the necessity of
having a fresh quantity proportionate to the nature of the
animal.   This will appear the more clearly from the  facts,
that birds breathe more than other animals  in proportion to
 their bulk, and  their heat is about 106°,  but the heat of
fish is never found near as considerable, nor their respiration.

   The  arterial blood being properly formed,  a most impor-
 tant question arises, concerning the means by which it is
 converted into the parts of  the body, and into  the secre-
tions.   This  has  long  occupied  the attention of  those stu-
 dying the nature of the animal body.  The more I have
 reflected on this  subject, the more  am I convinced that the
 common modes of accounting  for  such  phenomena, are
 far  from being perfect.  In my Inaugural Essay, I advan-
 ced a  new  theory on  the subject, on which the more I
 reflect,  the more does  it appear  to me to be the true expla-
 nation.   Of  the  correctness of this, I am further persua-
 ded by the concurrence of some of the first  characters  in
 the country.   But  a few  days  have elapsed, since I was
 favored with a  conversation on  this  subject,  with the
  learned Dr.  Hosack, an eminent practitioner of physic  of 
438
DISCOURSE XV.
New-York, and Professor of Botany in Columbia College.
This gentleman without any hesitation, assured me that he
believed the doctrine to be correct.  I  mention this, with a
view to induce others  to examine it more attentively, that
its merit or defects may be decidedly ascertained.   It may
not be amiss to extract the following  from my essay, from
which an idea of the theory may be formed.

  " When we contemplate the animal machine,  we are
struck with the extreme vascularity of all its parts.  This
is so general  and  considerable, that  the human body has
been emphatically  called a " collection of capillaries."  In
these capillary vessels  or small tubes, the most important
operations are performed;-for it is in these, that the blood is
so wonderfully modified, as to be adapted to all  the exi-
gencies of the system.  The most general  operation  we
notice, is the conversion of arterial  into venous blood.—
No part is exempt from this remarkable  process,  whereby
the properties of blood become so materially altered. While
we keep in  view the  uniformity and  the simplicity of  the
operations of  nature,  we will account for this phenomenon
on common principles."

   " It is an undoubted fact, that the form and properties
of most substances are variable, and depend on  the cir-
cumstances  in which  they are  placed.   By" experience
and observation,  we  learn what changes  can be produ-
ced,  and what  is necessary to produce them.    For  ex-
ample: of water,  we  find that in a low degree  of heat,
the particles cease  to roll on each other, and become so ar-
ranged as to constitute ice.   In a higher  degree  of heat,
another substance, the  egg,  is  deprived  of its  fluidity,
while  the solidity of  a  metal is lost in the same tem-
perature." 
DISCOURSE  XV.                *39
  u In accounting for such phenomena, we do not call in
the  agency of an  intelligent vis vita, or uncommon prin-
ciple ; neither can  they be  referred to one of the agents
separately.  We are to infer that they arise in consequence
of the natural tendencies or affinities of the substances, exer-
cised in consequence of the circumstances created by lessen-
ing or  augmenting the heat.   Let us extend this plan of
making inferences from facts to the human body."

  " But a little experience is necessary to teach us that the
arterial  blood,  like most substances, is susceptible of the
greatest changes,  and that these changes can be varied  with
the circumstances  in which it is placed.  For example,  in
the arteries we see it is of a vermillion color ; but, as Sir
Isaac Newton long since  observed,  in a particular position
it is yellow.   We see, also, that it loses its  fluidity when
allowed to  rest,  or placed in a  temperature above 160°.
When allowed to rest, the coagulating lymph of the blood
unites,  and becomes  solid.  This tendency of  the lymph
is also seen in the granulations of wounds, which being co-
vered with it readily unite together. The coagulum formed
by  the union of the lymph,  possesses some of the charac-
teristics of life.   These I presume are acquired in conse-
quence  of  the  union,  and  partial organization of the
lymph,  effected  by  the attraction  qf cohesion.  Hence,
such causes  (as lightning) which prevent  the coagulation of
the blood, must  operate  so as to destroy  the tendency of
the lymph to combination or organization.   Hence,  in in-
flamed  parts, where there is a  considerable quantity of
blood, there is an increased deposition of lymph,  and con-
sequently often a painful increase of irritability and sensi-
bility.   This, however, does not take place when the depo-
sition of  the lymph is in the cellular membrane, as in schir-
rus tumors.  But to return from this digression." 
440               DISCOURSE  XV.
   " When  the  blood is propelled  to  the small  capillary-
 vessels,  in  consequence of fibrous  action (which is  the
 only effect of fibrous action we perceive) the circumstances
 necessary for its continuance in  the state of arterial  blood
 no longer exist.  On arriving at the  commencement of  the
 veins, it takes on the properties peculiar to it in that state
 of parts by the exercise of its affinities, and  is thus  conver-
 ted  into  blood.  Here  we see the   agents, the solids of
 the  part  and the blood, as  in  the  cases  first mentioned.
 As the solids remain unaltered, the  effects we should refer
 to the exercise of the natural affinities of the blood in the
 parts,  just  as we do the various shapes  of water,  eggs,
 and  all  other substances in other circumstances."

   " If the above be correct,  we are led to look upon  the
 body as a laboratory in which the most important operations
 are  performed.  From the differences in  its construction,
 we naturally conclude that various compounds are  formed.
 And accordingly  we find that different processes go on, and
 that  compounds  different from  venous are formed  from
 arterial blood.  These   are  the  secretions so familiar to
 us all."

   "  Physiologists,  in accounting  for the secretions  since
 the rejection  of the  explanation on principles of mechanical
 filtration,  have referred them to chemical changes wrought
 by the actions of  the secreting vessels.  The only effect of
 the  action of a  collection of vessels forming a gland, or
 a compound,  that I  can perceive,  is to propel or convey the
 blood through it; and indeed it is to me incomprehensible,
how  the motions  of» simple tubes or vessels could possibly
produce changes in  any fluid.  I shall, therefore, wave the
consideration of the conjecture, and proceed to account for
the phenomena on the simple principles suggested above." 
DISCOURSE XV.
441
   « Although  we  be unable to  detect the particulars in
which one secreting vessel differs in its structure from an-
other, yet on the slightest attention we can perceive a very
material difference.  We can readily discover that the very
delicate hand of nature has made an astonishing modifica-
tion of even the most minute vessels.  From the various
structure  of all  the glans,  the blood when conveyed in
them, assumes in each,  in consequence  of exercising  the
affinities peculiar to it in the respective  states, the neces-
sary forms and properties.   Mr.  Home observes, that im-
mediately on leaving the vessels the secretions are fluid, and
acquire their consistence shortly after.   When the new
properties are  acquired,  the ducts or other tubes  convey
them to the parts for which they were formed.   It is thus I
presume, by the exercise of chemical laws, or affinities regula-
ted  by states, depending on the mechanism of parts,  that  the
         • supplies of all the secretions are created from the blood"
successive.
  « If this explanation be admitted, the vague conjectures
of physiologists relative to secretion must be laid aside.  In
place of  them we will have the plain facts,  that nature was
accurate  and wise when she so made the solids of animals,
that the  fluids  acquire in them by their own tendencies the
necessary form and properties.  Nor does she here demon-
strate more  forcibly, a delicacy  and wisdom in operating,
than in the structure of her master-piece the eye."

   « Our theory has something  more than simplicity  to
 render it plausible.   It will  enable us to explain  several
 phenomena which have excited astonishment."

    « The resemblance of  all venous blood, coming from
 parts  secreting very different fluids can  no longer appear
 mysterious." 
4-42
DISCOURSE XV.
  " The formation of an oily matter after death resembling
spermaceti,  and,  also,  other secretions are common occur-
rences.   Fourcroy,  by  a particular process, was enabled to
form bile from the blood of  an ox, which has been errone-
ously supposed to be a proof of  its being formed in  the
blood.   It must readily appear  from the invariable laws of
matter,  that whether the necessary circumstances for  the
formation of a compound exist  in the body before or after
 death, or elsewhere are created by art,  that such a com-
pound would be  necessarily created when  the constituent
parts are present.   Hence this leads us to expect, that from
the  improvement of our arts, all the  secretions  may be
formed by us at some future day."

   " There is a fact familiar  to most of us,  which  tends <o
prove the correctness of these  opinions.  This is the sup-
port which one  animal receives from  the secretions of  an-
other. It is true that some of these are more nutricious than
 others.   This in some  measure must proceed from a strong
 cohesion resisting  the lesser tendency to assume the form
 necessary for  nourishment.  The secretions having a  ten-
 dency to decomposition, afford a generous support,  and
 fat and milk are among the  most remarkable.   When these
 are swallowed they are dissolved by the gastric juice, con-
 veyed to vessels where they assume the form of chyle,  and
 then pass on to the blood, and assume on the same principles
 its properties.   Here we have, almost to demonstration, the
 same particles of matter in  the shapes of a secretion, then
 chyle, then blood,  in which last form it had existed."

   " There is a system of vessels whose office to the body
 -seems the reverse of that of the secretories.  This is form-
 ed by the absorbing vessels, which may be termed the sup-
porting system.    While the  first is engaged  in diminishing
 the  volume, the other is not  less active in renewing the 
DISCOURSE  XV.              443
blood. It is through these vessels that chyle is formed from
our food, and that  all  the  secretions  of  our body,  all tu-
mors, effused blood, matter, &c.  are returned to the blood.
In this  process we find nature adhering  to ^her beautiful
simplicity.  By a proper and  uniform structure of these
vessels,  the various  substances  on entering them,  assume
the same  appearances in consequence of their natural affi-
nities in that state, just as they acquired other properties
under different circumstances in other  parts.   When these
new properties are  thus acquired, it  is conveyed  to  the
blood vessels, where it is changed from  lymph  to  blood.
It is in this manner, in continued fevers, where no nourish-
ment is taken for weeks, that large quantities of  blood are
formed  from the secretions, the absorption of which must
be accelerated during the general increase  of fibrous action.
This is  confirmed by the circumstance, that the animals
in the north, during the winter,  are entirely supported  by
the absorption of fat—a secretion deposited in their cellu-
lar membrane."

   This is the theory by which we have accounted  for ve-
getable secretions and growth; and also for the changes  ta-
king place in those bodies which have hitherto received most
of the attention  of the chemist.  The uniformity, and  I
may add, the simplicity of the explanation or theory, ap-
pears to me an argument, in its favor, of  no inconsiderable
weight.

   When animal  substances  are formed, they possess  the
characteristics of life  only for  a certain time;  these  are
then lost, and the animal is said to die.   After death their
bodies  soon putrefy; in consequence  of  which,  numerous
 compounds  are  formed, which, as observed of vegetable
 bodies,  depend  on two causes; one  is  the particular ele-
 ments  present,  and the other is the circumstances in which
 these elements are placed. 
444
DISCOURSE  XV.
  The putrefaction of animal matter takes place iu propor-
tion to the number of elements in it:  that of a very com-
pound nature going on much more rapidly than that which
is composed of only two or three elements, as fat, resins, &c.
However, whatever be the composition of animal substan-
ces,  it is indispensably necessary that moisture  and heat be
present for putrefaction to take place; and in  general the
higher the temperature the more rapid is the putrefaction,
provided the heat be not too great,  in which case it carries
off the moisture.  It has  also been observed, that putrefac-
 tion advances more rapidly in the open air; but  exposure to
 the air is not necessary, although it modifies the process.

   When putrefaction  commences,   the bulk, color, and
 consistence of the body  are changed.   Various aeriform
 bodies are extricated ; these generally consist of  ammonia,
 or the volatile alkali;  of hidrogen air  holding sulphur, car-
 bon and phosphorus in solution; of carbonic acid, nitrogen
 air and water.   Miasma and nitric acid are, in some  cases,
 formed and emitted, and there remains behind  an earthy-
 like substance.

   In carcases buried under the earth, this process  goes on
  more 6lowly.  But when a great number of  carcases are
  crowded together in one place, and  are so abundant as to
  exclude the action of external air and other foreign agents;
  their decomposition is entirely the consequence of the action
  of  the component   parts  on each other.  The body is
  not  then dissipated, but   is found diminished in  size,
  and  converted into an oily  matter,  resembling  spermaceti.
  This singular change has not long since been noticed.

    About 1786,  the burial ground of  the Innocents in Paris,
  became so offensive,  that it was found necessary to remove
  the  numerous  carcases  which had  been heaped  on each 
DISCOURSE XV.              445
other, to another place.  On removing these, it was found
that the flesh had been converted into this soapy substance;
of a white color, soft and greasy to the touch.  With alka-
lies it formed soap,  and when set on fire, it burnt precisely
like oil or fat, only  that it exhaled  a more unpleasant
odour.

   On examining a pit at Oxford, where all the bodies which
had been dissected were thrown, Mr.  Gibbes found  the
same substance.   A small stream of water constantly pas-
ses through this pit; a circumstance which induced Mr.
Gibbes to try if animal muscle exposed to the action of a
running stream would undergo the same change. The expe-
riment fully succeeded; and consequently he attempted to
render this substance, to which he gave the name of sperma-
ceti,useful in those  manufactories which require tallow. And
a manufactory for  the purpose  was accordingly established
at Bristol.   This product, however, is found to have a  dis-
agreeable odour, but no doubt this might be corrected;  and
then persons dying, may have the pleasing reflection,  that
their bodies instead of affording food for disgusting insects,
will be exhausted in furnishing light for the illumination
of elegant rooms,  and other useful purposes.


              OF COLORING BODIES.


   IT now remains for us to  make a few remarks concern-
 ing the art  of

                COLORING BODIES.

   This may be divided into two branches; the  one called
 painting, the other dyeing  or staining.   The art of painting 
446
DISCOURSE  XV.
 depends,  as observed while considering'oils, on the appli-
 cation of one body, called a paint, to another.  It is neces-
 sary that it should adhere  to  the body to be painted; and
 hence the paints or coloring matter are mixed with linseed
 oil,  which on drying, acquires a considerable  degree of
 solidity.   The success  of this art depends  in a. great
 measure on the degree of intimacy with which the oils and
 coloring matter are blended together.

   The art  of varnishing  differs from that of common
 painting only in this, that the substance used as  a varnish
 should reflect strongly the light, so that it  may have a
 glossy or shining appearance.   Concerning the method of
 making varnishes, we treated  while considering the proper-
 ties of resinous substances.

   But the art of dyeing differs considerably from that of
 painting.   It depends chiefly on changing and giving other
 reflecting surfaces to bodies;  which can only be  done by
 means entirely chemical.

   Concerning the particular means of varying the reflecting
 surfaces of every substance,  it would not be possible for  me
 to dwell on in a work like this.   Some of these means have
 been occasionally hinted at in the course of this work;  and
 I shall now only mention the following.  No substance
 is found to produce more  considerable changes on  the
 surfaces of bodies than the light of the sun.

  The art of bleaching,  or rendering bodies in that state in
 which they reflect the rays of light, so as to excite the idea
 of whiteness,  appears to depend in great measure on the
 strong tendency  which  oxigen has to  unite with bodies,
 and form a white compound ;  at  least this holds good with
the products  of  the  vegetable  kingdom.   Hence,  the oxi- 
DISCOURSE  XV.
447
muriatic acid, when.united with water, is frequently used
to whiten many substances, as we before observed.   This
appears to act by yielding oxigen to combine with the dark
colored body ;  and on the same principle the long exposure
to air, to weak  acids,  to hot- water, &c.  of many sub-
stances is found to bleach or whiten them.

   Cotton is bleached  in some manufactories by the follow-
ing process :  to a boiler firmly fixed, a top is  adjusted in a
strong manner.  Potash rendered caustic by lime is put into
the bottom of this vessel,  and  the goods intended to be
bleached,  are put into a basket, which prevents their touch-
ing the sides  of the boiler.   When the articles are properly
placed, the covering is then fixed  on, which has  a  very
small orifice, to allow of  the escape of a part  of the steam.
By these means a degree of heat,  much superior to  that of
boiling water, is excited in the solution of potash; and the
heated water, aided by  the  potash,  destroys the  coloring
matter of the cotton and leaves it of a fine white color.

   It is found that it is not only necessary  to bleach articles
to be dyed, but to have them cleansed as perfectly as pos-
sible.   And  for this  purpose they are usually washed in a
strong solution of soap in water, which in some instances
dissolves a portion of the substance of the article and thereby
the better adapts it for being dyed.

   The substances used have as dyes been classed under the
two heads  of substantive  colors, and adjective colors,  by
Dr. Bancroft.

    1. Substantive colors are those, the particles of  which,
 of themselves have a sufficient affinity for the stuffs to  be
 dyed, to unite to them and remain fixed. 
448
DISCOURSE  XV.
  2. Adjective colors are those which have not of themselves a
sufficiently strong affinity to be fixed on the body,but require
some earthy, metallic or other body,  by which a bond  of
union is formed and the color fixed.   The body interposed
is called the base or mordant.

  Before the coloring matter will unite to the stuff to bedyed,
it is necessary that it should be in a certain state, which is
created by  its solution in water ; and most commonly the
presence of heat is also necessary.   It may be well to call the
water, heat, and  any other article necessary, agents, as they
are instrumental in creating the circumstances for the exer-
cise of the affinities between the articles  to be dyed and the
coloring matter.  These articles should be termed the actors.
Therefore, for dyeing a body, there should be (what is ne-
cessary in all cases  where the affinities of matter are exer-
cised)  first, a state for the exercise created by bodies, pro-
perly termed agents:  and  secondly, bodies  which  will act
on each other in such a state, which are properly termed
actors.

   Of  those actors in dyeing, which are called substantive,
in consequence of  not requiring any additional body to fix
them  on  the body to be  dyed, the most remarkable are
the following :  the husks of walnuts,  the roots of the wal-
nut  tree, shoemake or  sumach,  santal,  the bark of elder,
&c.   These are commonly termed root colors.  No prepa-
ration is required to dye with these  ingredients ; nothing
more being necessary than to boil the stuff in a decoction of
these  articles.  The most remarkable dye of this  kind,  is
the  famous Tyrian purple, which  is supposed to have been
discovered 500 years before Christ, in Tyre, and obtained
from  certain  shell-fish.  It was,  however, lost for many
hundred years, and was again discovered in 1685 by Mr.
 Cole,  in the shell-fish called the buccinum.  The shell which 
DISCOURSE  XV.              449
h considerably hard, is first broken by a small blow, taking
care not to crush the body of the fish within.   After pick-
ing off the broken pieces,  the juice is obtained from a small
vein near the head, when it appears of a white color,  and
feels clammy.   When this is applied to linen  or silk  and
exposed to the action of the sun,  it first appears of an  em-
erald green, then changes to a blue, and lastly  to a purple
red.   If the cloth be then washed with scalding water  and
soap, and exposed again to the sun, the color changes  to a
beautiful crimson, which  suffers no  further change from
exposure to the  sun.   The purpura, and an abundance of
snails are used also to dye the Tyrian  purple.   It is stated
that the green  fluid,  obtained from the common tobacco
worm, may be applied to useful purposes in the art of dye-
ing.

   Among the articles used in dyeing,  which may be called
adjective actors, in consequence of requiring a mordant, or
base, to fix the  dye, the  substance called cochineal is most
remarkable.

   This is  a  substance very  generally  known  and  used
to dye a rich crimson  color.  It  is  a  small,  irregular,
roundish body, and internally of a red color.  It is obtained
in great quantities from South America and St. Domingo,
where it  has been collected  with such secrecy, that  the
source  from  whence it  was obtained was long unknown.
Acosta, Sloane,  Plumier  and  other travellers have ascer-
tained, that  it is a small short  lived animal,  which is supr
ported by eating the leaves of the prickly pear tree.  They
are taken from the plant,  killed by boiling water, and are
then dried with care in the sun.  Several kinds are sold in
commerce; but  the best  is somewhat  heavy,  of a  grey
color  tending to a purple.   When chewed, it  tinges the
                          3L 
A50                DISCOURSE  XV.
spittle of  a  deep red color called crimson, and excites o»
 the palate a faint disagreeable impression.  When  quite
 dry, it has no smell.


   This article is much used to dye a scarlet color.  For
this purpose, several methods of preparation, &c. have been
recommended.    But all  these have been superseded by
 what has been  suggested by Dr. Bancroft.  According to
 the Doctor, a  beautiful scarlet color may be dyed  by the
 following means, which will be found less troublesome and
 expensive than any other.


   It is necessary to procure a quantity  of a yellow bark
 called the  quercitron bark,  which  is sold very  low.   A
 solution of tin in the nitric,  or nitro-muriatic acid, is com-
 monly used; but it is found far better to dissolve the tin in
 a mixture of the sulphuric and muriatic acids,  formed  by
 adding two parts of  the first acid to three of the muriatic.
 The muriatic acid is to be first poured upon a large quantity
 of powdered tin in a glass receiver, and then the sulphuric
 acid is to be added slowly;  when, by means of  heat, the
 solution  of the tin  is  expedited.   This murio-sulphate of
 tin is perfectly transparent and colorless, and may be long
 preserved for use.   This solution being  prepared, the cloth
 to be dyed scarlet  is to be put in a proper tin vessel nearly
 filled with Watetff with which about eight pounds  of the
 murio-sulphate of tin  is previously mixed ; the liquor is
 then^ boiled with  the cloth in it,  which should be turned
 through  it as  usual  for  fifteen  minutes; the  cloth being
 then  taken out, four  pounds  of cochineal, and two and a
 half of quercitron bark are to  be added  in powder ;  having
 mixed them well, the cloth  is to be returned into the li-
 quor, the  boiling  and agitation continued until the  color is
 duly raised, and the dyeing liquor exhausted, which usually 
DISCOURSE XV.               451
takes fifteen or twenty minutes.   The cloth is then to he
taken out and rinsed as usual.

   A scarlet color may be given to silk by the following pro-
cess.   Let the silk be soaked for two hours in the above so-
lution of tin,  with five times  its weight of water;  then it
is to  be moderately pressed,  partly dried,  and then dyed
in a  bath of  cochineal  and quercitron bark, four parts of
the first and three  of  the last.   Should  the color  not  be
bright,  the operation  may be renewed.  By omitting the
bark  and  dyeing the silk (prepared as  before) with cochi-
neal only, a very lively rose color may  be produced.

   Cotton may be dyed scarlet,  by  soaking it  in the above
solution of tin,  as proposed  for silk.  The superfluous
part of the solution is to be wrung out,  the cotton should
then be plunged in water, in which as much  clean potash
has been dissolved as will neutralize the  acid still adfiering
to the cotton, which is then to-be rinsed in clean water and
dyed with cochineal and quercitron bark.

   The article called  gum lac,  is a species of wax which
forms the cells of a  certain  insect.   It owes its beautiful
red  color to  the insect.   It is used to  color sealing wax,
red  morocco;  and for  several of the purposes to which
 cochineal is applied.

   But as before observed,  it is not consistent with the plan
 of  this  work to  enter  into particular details concerning
 the art of dyeing   In fact it would require a volume to give
 one half of the particulars;  for  the means of varying the
 color,  or reflecting surfaces of bodies axe innumerable.  Each
  dyer'will be found to  have some particular, peculiar to
  himself.  In such processes, care  should  always be taken. 
452
DISCOURSE XV.
to notice accurately what substances are requisite, their ex-
act proportions, and the state which should be created by
water, heat, light, &c.  for these substances to operate on
the surfaces of bodies.  Unless these be attended,  expe-
rience will prove of no use, and every trial will be found
varying.
44
SWSJWs
Spiff 
fc3* The following address I delivered  before the Philadelphia
   Medical Society, at their session in 1804, for the privilege
   of being an honorary member of that respectable institution.
   The doctrine it endeavors to support, is, thai animal life is not
   in  consequence  of the  agency of an  intelligent spirit,  called
   vis medicatrix, which regulates  the motions of the body, as sup-
   posed by one set of philosophers ; nor in consequence of its be-
   ing  the effect  of « stimuli acting upon the excitability of the
   system"  as taught by their successors ; but that it (life) is in
   consequence of the affinities of matter exercised on  each other,
   when the necessary states are created   A p rt of the doctrine
   here advanced wasflrst introduced into the Medical Society by
   the  accomplished,  and not less learned than eloquent, Dr. N.
   T.  Chapman, formerly  of Virginia, and at present  one of
   the practitioners of physic of Philadelphia.   It was solely
   with a view to lead to an investigation  of the  merits of the
   doctrine that this paper was prepared, and with that view it
   is now offered as a

               CONCLUDING ADDRESS.
Gentlemen,

     THE  detection  of error has  been almost uniformly
considered  as a step towards the attainment of truth.  In-
fluenced by this impression, many of the first philosophers
have recommended remaining without theories,in preference 
 454          CONCLUDING ADDRESS.
 t& the adoption of  such as are  unfounded.   Observing the
 tendencies of the mind, they could not fail remarking,  that
 the attachment to ideas was proportionate to their duration.
 But few causes have proved greater barriers to the prospe-
 rity of science than such attachments : they have lessened
 the energies of its prosecutors,  and have prevented the pre-
 valence of more noble feelings.   And men not animated
 by an adoration  of truth, but yielding to  the dictates of
 inclination,   could  not fail  to be  early  plunged in  the
 boundless ocean of  uncertain conjecture.   Here the sem-
 blance of truth,  attracting on all sides,  constantly dazzled
 and  deluded die most  daring  navigators.   Neglecting the
 surface,  and  diving towards the  impenetrable recesses of
 nature, they could only give the ravings of misguided spe-
 culation.  The general and false glare  serving to fascinate
 the  students,  successively  bewildered them too in  the
 mazes of intricate theories ! Hence ages have been marked
 only by the accumulation of error !  Hence confusion, de-
 lay, and wild suggestions, have characterized the  progress
 of science!

   In taking a retrospective view of  the attainment of our
 small stock of knowledge,  we  have  but a  sad  portrait of
the mind of man.  On the one side we behold the feeble-
ness of his power—on the other, the folly of his plans.   At
one time we find him grasping at  the intelligence of a Deity—
at another, in the convulsions of prejudice opposing  truths
accidentally revealed.   At one time we find him struggling
under  the  pressure of  difficulties—at another, exerting
his powers in lessening the influence of enlightened  bene-
factors!  These mournful  circumstances  have  militated
most  against  the medic art.   The dignity  of the science
has been debased, and its pillars ignorantly mistaken.  But
few within these walls are unacquainted with many of  the
groundless theories and  absurdities  which have engross^ 
             CONCLUDING ADDRESS.         455
the attention of physicians.  But  few have not felt varying"
emotions on  reading the details of the follies, the conten-
tions and the misfortunes of the faculty.   Even in our own
days,  are to be seen unhappy effects of a want  of proper
ruling principles, and of unanimity among  our brethren.
Ye young philanthropic votaries!  while you weep over the
melancholy  retrospect,  you should  not be  unmindful of
modern scenes! you should  make an advance! you  should
exhibit an example calculated to  reclaim such lamentable
perversion! At once sever yourselves from contracted habits,
and your souls will regale  on the inexhaustible  luxury  of
serving mankind.

   In early days, when the understandings of physicians were
uncultivated, in consequence  of the general ignorance, we
should  not be surprised at  the frivolous theories obtruded
occasionally on the world.   But that a period of many hun-
dred  years should roll on,  marked by revolutions without
number, and no determinate  point be fixed,  is a subject of
astonishment.  We should not, however, be surprised that
while their enquiries were veiled under the shroud of super-
stition, that an invisible spirit, a Godlike power, should be
called in to explain the  phenomena of life.   But that men,
when freed from such frights of fancy, would persist in sup-
 porting doctrines  of  an  intelligent  power  ruling  the
 body;  that they should voluntarily entangle  themselves  by
 entering the labyrinth,  and following the windings of little
 gods, of their own creation, is truly  unaccountable.  Fortu-
 nately, however, the cause of the spirits was forsaken early
 in the last age. There then arose a BROWN, possessed of a
 superior mind.    To  the boldness  of  originality he added
 profundity of research, which enabled him to dissever the
 fetters entangling the doctrine of animal life.  Scarce had
 the brilliant labors of this illustrious benefactor of the world
 been known, hefore new irradiations broke forth.  The  fa- 
456          CONCLUDING ADDRESS.
vorite votaries of chemistry felt the flash . Their minds ex-
panded at the vivifying impulse ; they acted, and the value
of their works is daily increasing.  The science, though but
in its infancy, is eminently conspicuous.   Already has it re-
velled many of the late arcana of nature.

  Among the vague conjectures  of ancient or of modern
times, buc few are possessed of more plausibility than those*
of the once celebrated des Cartes.  His system of the plane-
tary motions, although arrayed in all the pomp of mathema-
tics, has not escaped a proper exposition.   The detection of
its fallacy, and the divine satisfaction of discovering the true
principles, were reserved for the sagacious Newton.  It was
he who correctly observed the motions, and referred them
to the attractions; to the laws of matter.   And much is it
to be  regretted, that .the  study of such laws has not been
more  universally the delight of  his successors.   Physicians
jt seems, became either blinded by the brilliancy of his la-
bours, or were too fond of mysteries,  to descend to the con-
sideration of the simple laws of the matter around  them.
The  failure  of all their trials,  might at least  have taught
them  where it was  folly to travel.   So far from explaining
the operations of animal bodies, they have been unable to
draw lines of distinction between the animal and vegetable
kingdoms.   Nature  knows nothing  of such  distinctions:
artificial  separations she refuses to  admit.  The  striking
similarity stamped on all her productions,  unquestionably
displays the uniformity of her manner of operating.   Her
circle of decompositions and recombinations, effected en-
tirely by the affinities of  matter,  demonstrates the extent
of her power, while it  announces the importance of the
bodies around us.   Let us turn our attention to some of
her works and contemplate the excellence of her ways. 
CONCLUDIVG  ADDRESS.          457
   An alkaline solution is placed irt a vessel before us.   If
to this an acid be added, an action  will ensue, a new sub-
stance will be formed, and its qualities will essentially differ
from those Of the ingredients. So it is when'you pour alcohol
on a concentrated acid in a certain degree of heat.   These
substances act on each other,  and the remarkable com-
pound, ether, is generated,  The burning of a candle be-
fore us, i9 on the same principle.  The tallow, in a high
heat, attracts and unites td the oxigen, at which time heat
and light are set at liberty.  Every one agrees in referring
these and similar changes to the attractions," or affinities,
or laws of the respective bodies, in the states in which they
are applied to each other : and we  might term the  union
of the substances the generation, the sensible action the life,
and its duration the period of existence.

   In the vegetation of plants we are equally struck with
such phenomena.   We place -a particle of matter pecu-
liarly organized,  called a teed, in a  mixture of  earths, car-
bon,  and water, termed a soil; and through the agency of
a moderate heat, these particles act on each other: the seed
attracts and combines with portions of the bodies around it,
by which its bulk becomes enlarged, and all its properties
are changed.    The bulk of this newly formed mass will
depend on the structure or arrangement  of the constituent
parts and the weight on the quantity of  substances attraGt>
ed from the earth.   The superior parts of the plant  on
coming in contact  with carbonic acid attract  and combine
with its carbon, while its oxigen is disengaged for the res-
piration of animals.  The plant being formed  by the exer-
cise of affinities in a eertain state, readily has these affinities
varied by change of state or circumstances.  Hence, vege-
table bodies are found in the'cold seasons  to be materially
altered   Hence,  in the fall they  frequently wither and
                          3 M 
458          CONCLUDING ADDRESS.
die.   A part  of their carbon unites to the oxigen of  the
surrounding air,  forming carbonic  acid  to nourish  other
plants in future times, and the  remaining parts fall down,
and  re-combine with  the earth in states of  combination
depending on  accidental  circumstances   Such operations
are explicable, without the  forced  interposition of any vi-
tal principle,  excitability, or any other imaginary quality.
The phenomena are obviously the effect of the affinities of
matter, exercised in the various circumstances or states.
Why then follow the common  custom of  calling  in the
agency  of  any unnecessary  principle or  property ?   Shall
we not follow  the valuable advice of Lord Verulam ? Shall
we contrary to the first rudiments of philosophy, reject the
most simple explanation of facts ?

   Let us extend our views a little farther; we will find a-
nimals  unquestionably formed  by the  affinities of matter.
For this, we  must recal to our minds  the experiments of
Count Rumford, and the Abb- Spallanzani.   The former
gentleman boiled for some time, a quantity of vinegar,  and
during the ebullition,  glass vessels were filled with it,  and
then hermetically sealed.  After remaining in this state at
rest for several days,  the Count discovered that a number
of little animals had been formed in the vinegar, and were
traversing the  fluid.   These animals are here  the more rea-
dily produced, as  the acetic acid may be easily decompo-
sed, so that its particles may react on each other.   But the
experiments of Spallanzani  are still more decisive.   Being
repeated frequently and related with the  habitual accuracy
of this celebrated naturalist they can be strictly relied on.
In a number of small glass vessels,  he  put equal quantities
of seeds, filled them with  water, and  then hermetically
sealed  them.   They were all subjected to great degress of
heat for different periods.   After  they had undergone the
action  of the  heat, they were  laid aside for several days. 
CONCLUDING ADDRESS.         459
On examination,  this excellent philosopher invariably ob-
served that the number of animalculse formed in the vessels,
was proportionate to the duration of the heat to which they
had been subjected.  The seeds, for example, boiled two
hours, contained four times as many animals as those boiled
but thirty minutes.   Here  we  see the recombination pre-
cisely proportionate to decomposition.  Surely, the animals
were formed by the action of the particles of the matter on
each other; for what germ could have sustained so great a
heat,orwhatvital principle could resist so powerful an action?

   The worms found in the kidneys, livers, and other parts
of animals, further confirm this doctrine.   It is too great a
stretch of the imagination to suppose that a germ could  be
taken into blood vessels, circulate through the  whole sys-
tem,  and then accidentally be  deposited in parts properly
adapted for its  growth.   According  to our theory, these
insects are formed  by the combination of certain particles
of matter coming  in  contact, under  the proper circum-
stances created in the body.

   It  being thus almost demonstrated, that animals of the
inferior  class may be  created by the  action of matter on
matter,  we will glance at a higher order; we will advance
to view the formation of man himself.   The embryo can-
not be prepared, every one knows, without the union of
 male an female secretions, requiring 1 believe not only the
 existence of the  necessary circumstances, but the presence
 of oxigen air.   The early re-action, the subsequent union
 with  the maternal blood,  and the consequent  increase of
 .bulk, are the effects of  affinities ; the particulars of which
 we cannot at present explain.   We can only now account
 for a few of the processes in this complex apparatus.  After
 birth, the lungs act as a chimney place to the body;  for
 there the blood  absorbs oxigen which at the time loses a 
460          CONCLUDING ADDRESS.
part of its latent  heat, which is afterwards further lost by
the changes wrought in the blood in different parts.   The
stomach  is a  vessel serving as a retort, in which the  food
is dissolved by a fluid before it can nourish the body.   The
fluids sometimes  acquire an  unusual capacity  to combine
with sensible heat;  and hence the body suddenly feels very
cold.   All the secretions of the body also appear to be the
effect solely of the exercise of  the  affinities of the fluids,
in the various states existing in  the machine : a decompo-
sition and recombination are constantly going on  in the
body.  The formation of the teeth is universally known to
be the effect of a pure crystallization of the  phosphate of
lime.   And to a kind of  crystallization are we to attribute
the coagulation of pure blood when at rest.

  In diseases we have instances  of such chemical operations
still more obvious.  Diabetes  is  characterized by the chemi-
cal  union of carbon, hidrogen and oxigen, forming sugar.
In  gout, we have concretions or crystals of the lithate  of
soda.   The  urinary, biliary,  and other calculi,  found  in
the body, must assuredly be formed in the  same manner.
And  the ulceration  of  muscular fibres,  is  known  to
arise in a great measure  from  their combination with the
oxigen of theair, forming fetid compounds.   In a low de-
gree of  heat,  called the extreme of cold, we know that the
fluids strongly re-act on each,  and acquire the appearance
of a black mass;  a process called mortification.

  If this theory be  admitted, we perceive at once the si*
milarity of nature's manner  of  operating.  She has given
to matter, laws, which come into action when  under cer-
tain circumstances:  by varying the quantities of this matter,
in a great degre,  and by still  more  varying  the states or
circumstances  in  which it produces  effects, she has made
ample provision for forming  her  innumerable productions 
             CONCLUDING  ADDRESS;          461
from the combinations of bodies to  unite to plants, up to>
the combinations for the head of man.  Once, gentlemen,
familiarize yourselves with the idea, and  it will  appear as
surprising, that  the fine fluids,  heat and light, should be
extricated, when oxigen combines with  carbon,  as  that;
our intellects, stated to be portions of  an ethereal spirit,
should be separated from the blood, when brought into the
delicately organized vessels of the brain, by laws peculiar
to itself.

   If this theory  be admitted,  how much ought  we to"
value our powers ! how wide are the fields for experiment-
ing !   To form any  product, all that  we have  to do,  is
to create the necessary state,  and add the  necessary articles
which experience teaches to be  proper.  The sole  objects
then of a chemist,  are first to know precisely the constitu-
ent portions  of a compound, and then to acquire the art
of forming the particular circumstance  for such portions to
act on each other.  When indulging our imagination, and
viewing what chemistry was a few years back, and what it
now is; where can we set bounds to our expectations!  You
know that the science is but lately freed from the fetters of
Egyptian hieroglyphics; its embryo is just emerging from the
troublesome  trammels  of  alchemy.   ; The conductors
now  cherished  in the bosom  of  nature;  almost   om-
nipotent, because united, "will  not be retarded  in their
progress.  Let   their  successive  generations  go cordi-
ally hand in  hand,  and atonement  may soon be made for
the misdirected industry of ancients.   A knowledge of all
the laws of matter may yet  be acquired: and then we will
find persons vieing with nature in forming the  most valuable
productions.   Nor will active and revolutionary man rest
with such success! Growing tired with the tardy operations
 of nature, he will seize at once her agents,  and will in  a
 few moments combine them, thereby forming all the articles 
462          CONCLUDING ADDRESS.
used as the necessaries and the luxuries of life.  Perhaps too
he may progress still  more.  By a zealous industry,  and
cordial union, possibly he may be able by his art to prepare
the state,  to  ascertain the constituents,  to apply them to-
gether so  as to crystallize a  man!  All other  collateral
branches  will proportionably improve-    And when a man
is thus formed, the artists may be able  to rob the heavens
of their electricity; to  convey  it at pleasure through our
immense mines of carbon, converting them into diamonds,
and with these erect  a refulgent  mansion  for his earthly
residence I
 
              DEFINITIONS

                   OF THE

      TECHNICAL TERMS

UNAVOIDABLY USED IN THE WORK.
Acetic acid.  This  is the acid" which gives  the sourness to
  vinegar.
Acetates, are the substances containing the acetic acid.
Acetous acid, is an acid containing less oxigen than the acetic
  acid.
Acetites, are the substances containing the acetous acid.
Acids, are sour substances possessed of certain general pro-
  perties, enumerated page  101,  of which there are three
  kinds, the mineral, animal and vegetable.
Affinity, chemical attraction, a law of  matter.
Air, an invisible  fluid,  our  atmosphere is an example.
  Great varieties of it.

^knoT* \ existing in the StatG °f airS'          %
Albumen,  the name of  a  part of animals resembling the
   white of eggs. 
464
DEFINITIONS.
Ammonia, the volatile alkali.
Alcohol, pure ardent spirit.
Alkalies,  substances possessed of  certain general proper-
  ties, enumerated page 145.
Alumine, name of  an earth.
Alum,  a  neutral salt, formed by the sulphuric acid  and
  alumine.
Aloes, name of a vegetable substance.
Alloys, the name of compounds of metals.
Amalgams, the name  of alloys containing mercury.
Apparatus, any particular machine.

                           B

Balsams, vegetable bodies,  formed by an oil and a resin.
Bases.  This word is  used in different senses  by chemists,.
  It signifies  the chief  part of compounds: we have
  bases of the airs,  as nitrogen, oxigen,  hidrogen,  &c.
  bases of acids,   as phosphorus, sulphur,  or any  sub-
  ; stance which unites to oxig&n so as to become acid ; then
  we have the bases of  neutral salts, which  are all the sub-
  stances that unite to the acids: and lastly, we haVe  the
  bases or mordants of dyes, which are articles used to fix
  the dye on cloths.
Bleaching, making' white.
Brewing,  preparing fermented drinks.

                           C

Calx, a metal united to oxigen, called oxid by chemists.
Combustible,  may be burnt, inflammable.
Caloric, the name of heat or fire,
Calcareous earths, of the nature of lime.
Carbon, the name of  a substance which when pure is called
  diamonds. 
DEFINITIONS.
465
 Carbonic acid, an acid formed by the saturation of carbon
   with oxigen.
 Carbonates,  axe neutral salts containing carbonic acid.
 Charcoal, an oxid of carbon,
 Citric acid,  the acid of lemons.
 Coagulation, rendering hard.
 Crystallization, conversion into particular shapes.

                            D

 Detonation,  explosion.
 Ductility, capability of being drawn into wires.
 Dissolve, is to chemically combine a solid with a fluid.
 Dyeing,  changing the reflecting surfaces of bodies.
 Decoction, water containing part of a vegetable  substance
   dissolved by means of heat.
 Distilling, separating volatile substances by means of heat.

                            E

 Effervescence,  is the escape of an air from a  solid so as to
   make a kind of hissing  noise.
 Elements, are bodies which cannot be decomposed.
 Ether, is the name of a volatile compound,  formed by the
   union of  an acid and alcohol.
Evaporation,  is the carrying  off  a body  by   means  of
   heat.
Earths, are substances possessed of certain general proper-
 .  ties enumerated in page  169.

                            F

 Fermentation,  is a  process  depending on  the  re-action
   of the constituents of a compound fluid.
                          3N 
466
DEFINITIONS.
Fulmination, detonation or explosion.
Filiates, neutr.-l s .Its containing the fluoric acid.
Fibrina,  the  name of  a substance found in the blood,  and
   forming a part of many animal bodies.
Fecula, the name of a substance found in vegetables, called
   also starch.
Fusible,  which may be fused or  melted, or made fluid by
   means of heat.

                           G

 Gas, an air.
 Gazeous, aeriel or aeriform.
 Gastric jtike, a secretion  from the stomach.
 Gu-cn,  the  name of  a substance forming a part  of vege-
    table bodies.
 Gelatine or jelly,  the  name of a substance forming a great
    part of animals.   When nearly pure it is called glue.
 Galvanism,  is a fluid  also called animal electricity.

                           H.

 Hidrogen, the name of a substance generally obtained by the
    decomposition of  water.
 Humid, wet.
                            t
 Indigo,  the name of a vegetable substance used in  dyeing.
 Isinglass,  the name of a  substance obtained from  whales.
 Inflammable, may be  burnt, or combustible, or oxidable.
 An infusion, water containing part of  a vegetable in soku
    tion.

                            L

 Laboratory, a place where chemical operations are performed.
  Lav*)  d  substance emitted during the eruption or burn-
    ing ot  voicanoes. 
DEFINITIONS.
467
Latent, hidden, combined, insensible.
Lutes, substances used to connect vessels together.
Lustre, reflection of  light.

                           M

Malic and, acid of apples.
Malates, neutral salts containing the malic acid.
Muriatic acid,  the name of an acid obtained from common
   salt.
Muriates,  are  bodies containing muriatic acid.
Mucilaginous,  containing slime or mucilage.
Miasma,  name of the substance causing fever in animals,
   and called contagion.
Mordants, bases or articles used to fix dyes.
Metallic,  of the nature of  metals.
Musk, an animal substance.
Mineralsgy, relating to minerals.
Minerals,  bodies  obtained from the earth.
Metallurgy, the art of reducing or assaying ores.

                           N

Nitrogen,  the name  of an  elementary substance  obtained
   ftoiii nitre.
Nitric acid, an acid commonly called aquafortis.
Nitrates,  neutral  salts containing nitric acid.
Neutral salts,  are compounds  formed by the acids, and the
   bodies or bases to which they unite.
Native metals,  are those found in a pure state in nature.

                           O

Qxigen.   This is the  name  of the  elementary substance
   which  readily  unites to other bodies,  forming in some
   instances acids. It is supposed to be the cause of all acidity. 
468
DEFINITIONS.
Oxids.   These are substances which contain oxigen, and are
  not acid. The metallic bodies form the most remarkable
  oxids-  which  are named according to the metal : hence,
  we have the oxid of iron,  oxid of tin, &c.
Oils, are substances possessed of  general properties familiar
  to every one.   Those obtained from vegetables are called
  fixed,  or expressed, and essential,  or distilled oils.
Ores, are minerals containing metals.

                            P
Process,  manner of operating.
Precipitate, is a  substance thrown down from its solution in
  a fluid by the addition of  another.
Precipitant, is a substance added to precipitate another.
Pyrometer, is the instrument to measure the degree of heat:
  invented by Wedgwood.
Pneumatic apparatus, is a machine used for airs, represented
  in plate II.
Phosphorus, the name of an element.
Phosphates, neutral salts containing phosphoric acid.
Pyrites,  are ores containing sulphur, called also hepatic ores
  and sulphurets.
Pottery ware, vessels  made  of  earths.
Putrefaction,  decomposition depending greatly on the re-ac-
  tion of the constituents of a compound,  as  fermenta-
  tion ;  and is characterized by the emission of ammonia.

                            R

Rarefaction,  dilatation by means of heat.
Retort, a vessel represented plate  II.
Resin, a substance obtained from vegetables.
Respiration, bredthing.
Refrigerator, a vessel for cooling.
Receivers,  are vessels destined to receive the contents of
  other  vessels. 
DEFINITIONS.
469
                            S
Salts % are substances remarkable for their solubility in wa-
  ter.
Specific  gravity, is  the relative weight  of a given bulk of
  matter.
Solution, is a fluid containing a solid dissolved in it, or che-
  mically united.
Saturated solution, is one which will dissolve  no more of a
   solid.
Solar phosphori,  are  substances which emit light in the dark
   without heat.
Sublimed, raised by means of heat.
Sacharine matter, sugar.
Sulphates, are neutral salts containing sulphuric acid.
Soaps,  axe compounds formed by oils and alkalies.
Sebacic acid, acid of fat.
Suberic acid, acid of cork.
 Succinic acid, acid of amber.
 Silicious earth,  is silex, more properly spelt sileciousr

                             T

 Torrefied, roasted in the open air.
Tincture, is  ardent spirit containing some  part of a  vege-
   table in solution.
 Thermometer,  an instrument to measure the degree of  heat.
 Tannin, is  a substance which unites to the  gelatine of hides
   forming leather;  and the process is called tanning.

                             V

 Volatilized,  that is  evaporated by means of heat.
 Volatile, readily evaporated. 
BRISBAN   &  BRANNAN,

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     HAVE just received from London, a large addition to their former stock;
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                       CURRAN'S SPEECHES.

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ADVERTISEMENTS.
superior cast, who in the skilful management of all the beauties and energies
of the English language, delivers his opinions
            " In thoughts that breathe, and words that burn."
  " There are limits to the human genius, which bound the exertions even
''' of the most comprehensive and vigorous mind—those  limits we do sin-
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  Charles  Fox h as been  considered the greatest  orator the woi Id has ever
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same assembly.
                     LIFE  OF CUMBERLAND.

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                     LIFE OF  MALESHERBES.

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ADVERTISEMENTS.
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                      MASSILLON'S CHARGES.
BRISBAN  fii" BRANNAN, have lately published, in a neat octave volume,
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  The species of eloquence which prevails throughout these discourses is
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