A Study of the Soil in Relation 
to Health and Disease. 
By George Kober, D., 
OF FORT BID WELL, CALIFORNIA. 
Reprinted from Virginia Medical Monthly, May and June, 1894. A STUDY OF THE SOIL IN RELATION 
TO HEALTH AND DISEASE. 
By GEO. M. KOBER, M. D., 
OF FORT BID WELL, CAL- 
[Reprinted from Virginia Medical Monthly, May, 1894.] 
The health of a locality is intimately connected with the 
character of the soil on which our habitations are built. 
This was recognized by the father of medicine, Hippocrates, 
who pointed out the relations of soil to certain fevers and 
their general effects on the constitution of man ; and we 
know that over 2400 years ago attempts were made to drain 
the Pontine marshes and those of the Velubrum. All these 
efforts were based upon empirical knowledge; and although 
Lancise and Moscati, over one hundred years ago, made a 
microscopical examination of soil and the air condensed in 
rice-fields with a view of demonstrating the nature of mala- 
ria, it remained for Pettenkoffer to formulate exact methods, 
by which investigations of the soil, ground-air, and the 
ground-water and its fluctuations might be carried on, and 
their relations to health and disease—especially the infec- 
tious diseases—be explained. It is hoped that this arti- 2 
cle may stimulate contributions to the geographical history 
of diseases in this country. 
1. Nature and Composition of Soil.—By the term “soil,” we 
mean here the upper or superficial portion of the earth’s 
crust, which directly or indirectly supports animal and 
vegetable life, and which is therefore capable of affecting 
health by one or more of its properties. 
All soils are composed of mineral, vegetable, and some- 
times animal substances; and the character is largely influ- 
enced by the relative proportion of the different constit- 
uents, the dimensions of the fragments and the degree of 
their consolidation. 
The mineral constituents of the soil may be derived 
from primitive rocks (granite, basalt, trachyte or porphyry), 
and stratified rocks like limestone, sandstone, slate and 
clay. Originally, they were all composed of sand and clay, 
and these constituents either occur alone or are intermin- 
gled in various proportions. The fine particles of soil are 
simply disintegrated rock, the result of the elements, and 
as the soil sustains vegetation, it is perfectly natural that it 
should also contain vegetable matter. Forests have been 
buried and again elevated, constituting deposits; vegetable 
debris is derived from plants, and is known as peat, humus, 
etc. In some places, especially in the sandy plains, near 
foot hills, the rain washes down finely-powdered debris and 
is filtered as it passes through the soil, so that each grain of 
sand may be encrusted with a film of vegetable matter. 
The remains of animals are found in all but the primi- 
tive rocks; and whilst the animal constituents have gener- 
ally disappeared, yet occasionally they have been distinctly 
traced even in the tertiary strata. On the surface, there is 
perhaps no soil which does not contain some animal matter. 
These accumulations of rocks and soil form layers of 
various depths on the earth’s surface. In some localities, 
the impermeable strata crop out on the surface, whilst else- 
where they may be buried with loosely-consolidated mate- 
rial for a distance of a hundred feet or more—a matter of 3 
importance in the question of wells, springs and ground air. 
Comparatively speaking, even the hard rocks—granites 
and metaphoric rocks—cannot be considered impermeable ; 
and between these, the dense rocks, the softer rocks and the 
loose soils covering them, we find, of course, different de- 
grees of porosity and permeability. Delesse (.Bulletin So- 
ciStS GSol. de France, 1861-1862, p. 64,) has shown that solid 
rocks may absorb water in the following amounts: 
Granite =0.06 per cent, to 0.12 per cent, of its weight. 
Slate =0.19 per cent. “ “ 
Sandstone =0.66 per cent, to 13.15 per cent. “ “ 
Basalt =3.03 per cent. . “ “ 
Oolite =3.29 per cent. “ “ 
Limestone =9.67 per cent, to 21.10 per cent. “ “ 
Chalkstone =24.1 per cent. “ “ 
Since the water could only have entered the interstices 
before occupied by air, the figures demonstrate the relative 
porosity of these rocks. If, however, we apply the same 
test to weathered fragments or the disintegrated rocks, we 
find that whilst a solid piece of granite could only absorb 
0.06 per cent, of its weight of water, granite, in the form of 
a powder, can take up 27 per cent, of its weight of water. 
Of the different kinds of soil which interest us most, the 
fine agricultural soils have the greatest number of pores, 
and gravel and sand the least number. The total number 
of pores varies in different soils, as follows: (Wolff, Fliigge 
and Erismann.) 
In fine garden soil, 64 per cent, of the total volume. 
In black sandy clay soil, 56.08 per cent. “ “ 
In fine sandy clayey soil, 55.3 per cent. “ “ 
In very clayey soil, 46 per cent. “ “ 
In sandy soil, 35.5 per cent. “ “ 
In sandy clay, 32.7 per cent. “ “ 
In average fine gravel, 35.3 per cent. “ “ 
In coarser gravel, 35.24 per cent. “ “ 
2. Ground Air.—The interstices and pores of the soil are 
necessarily occupied by air, if not by water. This air is 
called ground-air, and although connected and interchange- 
able with the atmosphere, differs in this, that it contains 4 
less oxygen and more carbonic acid. Oxygen is present to 
the extent of 15-20 per cent, of its volume, whilst carbon 
dioxide may be present in from 1 to 25 volumes per 1,000 
and more. This is due to the chemical changes which take 
place in the soil, in which oxygen is consumed and C02 
is evolved. Apart from this, we find ammonia derived from 
decomposition in the soil or imbibed from the atmosphere, 
the amount has been estimated from 0.0089 to 1.20 mgrm. 
per cubicmeter. Carburetted hydrogen and hydrogen sul- 
phide have also been found, and even coal gas, which had 
escaped from defective pipes. 
Dr. Nichols made an interesting series of experiments on 
the ground-air in the back bay lands of Boston. In his first 
experiments the air was drawn from 3| to 5| feet; there 
was no hydrogen sulphide and only a little ammonia; the 
CO2 was from 1.49 to 2.26 volumes per 1,000, and varied 
inversely as the height of the ground-water, which was very 
near the surface. This relation was not constant at a depth 
of 6-10 feet. These observations and those of Fodor, Fleck 
and others, indicate that at a depth of thirteen feet, the air 
of the soil contains enough carbonic acid to extinguish a 
light, and certainly would be irrespirable. When we con- 
sider the depth of some of our cellars, and the fact that cel- 
lar-air often enters the house, we see at once a good reason 
for cementing our basements; but apart from this, ground- 
air may also harbor micro-organisms and disease-germs, 
which have been liberated from dry or pulverized soil, add- 
ing additional elements of danger which will be referred to 
later. 
The composition of ground-air is of special importance, 
because it is in continual movement and connected with the 
atmosphere, by which interchange of gases can take place 
and thus affect the air of our habitations. The move 
ments of ground-air have been demonstrated by mano- 
metres, and are influenced by the diurnal variation of the 
temperature of the soil, the rain-fall, and the rise and fall of 
the ground-water. As the ground-water rises, it displaces 5 
the air from the soil; when the water sinks, air enters to 
occupy its place. 
Fodor considers these factors, as well as alterations in ba- 
rometrical pressure, together with the action of winds forcing 
air into the strata, all more or less essential in the move- 
ments of ground-air; it must also be apparent that loose 
porous soils offer the least resistance to the movements of 
ground-air. Apart from this, other local conditions play an 
important r61e, especially when the soil is covered with a 
house and the building heated with a furnace placed in a 
basement not cemented ; in such a case, the objectionable 
ground-air may be drawn from great depths. Indeed, it 
has been shown that coal gas escaping from pipes and pre- 
vented from exuding by frozen earth on the surface passed 
sideways for some distance into houses. The air of cess- 
pools and defective sewer-drains have likewise found their 
way into dwellings, and the examination of drains alone 
often fails to detect the cause. Houses erected over “made 
soil/’ usually formed of house refuse and dry rubbish, are 
notoriously unhealthy and justly attributable to the con- 
stant ascent of impure air from the impure soil below into 
the warm rooms acting as aspirators above. 
3. Ground- Water.—Water is one of the constituents of soil; 
for it is almost invariably present in the form of moisture 
and ground-water. When the soil is simply moist, we know 
that air and water are both present; but when all the inter- 
stices are filled with water, we have liquid mud, and have 
reached what Pettenkoffer defined as ground-water. The 
moisture of soil depends on its capacity to absorb and hold 
water, and on the supply of water in the soil either from 
rain, irrigation or ground-water. Meister gives the follow- 
ing table, showing the capacity of different soils for absorb- 
ing water: 
Sandy soil has a capacity of 45.4 vol. per cent. 
Quartz sand soil “ “ 46.4 “ “ 
Chalkey soil “ “ 49.5 “ “ 
Blue-clay soil “ “ 50.5 “ “ 
Gypsum soil “ “ 52.4 “ A 6 
Limestone soil has a capacity of 54.9 vol. per cent. 
Clay soil “ “ 60.1 
Peat soil “ “ 63.7 
Agricultural earth “ “ 69.0 
Humus soil “ “ 70.3 
Apart from the size of the fragments and the porosity of 
the individual particles composing it, the presence of organic 
matter vastly increases the absorbing and retaining powers 
of the soil. The chemical qualities of the soil likewise in- 
fluence these properties. This is shown by the difference 
in quartz and clay soils, the grains of which have the same 
dimensions, but the former only absorb 3.66 vol. per cent., 
against 31.05 vol. per cent, of the latter. Whilst no soil is 
absolutely impermeable to water, for practical purposes 
they may be divided into permeable and impermeable soils. 
The former include chalk, sand, sandstone and vegetable 
soils; the latter, unweathered granite, trap, porphyry, gneiss 
and feldspathic rocks generally, also clay, slate, dense clays, 
hard oolite, hard limestone, etc. 
The amount of rain which may pass into any given soil 
is of course influenced by the declivity and inclination of 
the soil, by the amount of evaporation, which is always greater 
in summer and during hot wrinds, and by the rapidity of the 
rainfall itself, which may be pouring down faster than the soil 
can absorb. Parkes estimates that on an average about 25 per 
cent, of the rain penetrates into the sand rock, 42 per cent, into 
the chalk, and from 60-96 per cent, into loose sand formations. 
The remainder evaporates or runs off the surface by natural 
drainage. It will be readily understood that by capillary 
attraction the upper layer of the soil may be kept moist 
from the subterranean water, even though evaporation is 
constantly going on at the surface; and this process is im- 
portant from a hygienic point of view, because it attracts 
the moisture from deeper layers and may thus carry micro- 
organisms to the surface, which, if the evaporation goes on 
to the extent of dryness, may be liberated from the pulver- 
ized soil and carried with the dust into the air. 
All the water from the surface, by reason of its gravity, 7 
sinks and continues to do so until it reaches a point where 
all the interstices are filled with water, and here joins the 
subterranean water-courses. This may be at variable depths 
in different soils; sometimes it is only two or three feet from 
the surface, and it may be several hundred feet, depending 
largely upon the elevation above the surrounding country, 
the depth of the impermeable stratum, or “ hard-pan,” and the 
care with which the underground-water flows towards its natu- 
ral outlets. It is not necessarily a horizontal underground 
sheet of water, for some impermeable stratum may crop out, 
opposing its further movements, and convey it in the form of 
springs to the surface. In low plains and valleys, the under- 
ground-water is generally not far from the surface. The 
movements of this water are constant in the direction of its 
natural outlets, which are springs, water-courses and the 
sea. The rate of this flow is influenced by the compactness, 
porosity and inclination of the soil, whilst the roots of trees 
naturally also lessen the movement. 
According to Hess, the rate of movement of this ground- 
water is from forty to one hundred feet a day. Soyka deter- 
mined a movement of 160 to 6,000 feet a day. In Munich, 
Pettenkoffer estimates its rate at fifteen feet daily. Fodor 
gives the mean rate at Buda-Pesth at 174 feet, with a maxi- 
mum of 216 feet in twenty-four hours—calculated by the rise 
of the wells following a rise of the Danube. 
The level of the ground-water is also constantly changing. 
This has already been referred to. It naturally rises after 
heavy rains; but the effects of rains are sometimes not per- 
ceptible until weeks or months after the fall; the rise and 
fall is sometimes quite rapid, depending on localities and 
seasons,its movement may be only a few inches either way; 
but in most places the limits between its highest and lowest 
levels in the year are several feet. In Munich, it is ten 
feet; in some parts of India, it is seventeen feet; in this 
Valley, it is fourteen feet. 
There is generally a periodic rise, commencing in the fall 
of the year, and a corresponding depression in the spring, 
which has been attributed to the increased percolation of the 8 
rainfall in the colder months and the greater evaporation in 
summer. The level of ground-water is also influenced by 
the pressure of water from the rivers or the sea, geological 
obstructions to its outfall, etc. When these obstructions are 
very great, the ground-water, stagnates and we have our 
marshes, and swamps, and tule lakes; these, when inland, 
are entirely due to the fact that the subsoil-water is held up 
by impermeable strata, and the water has no outlet except 
by evaporation. 
4. Absorption of Heat and Temperature of the Soil.—The tem- 
perature of the upper layers of soil depends largely upon 
its exposure to the sun; but it is well known that the heat 
is absorbed in different amounts by different soils equally 
shielded or unshielded by vegetation, and that it depends 
largely upon the color of the soil. Dark soils absorb more 
heat than light-colored soils, and the dimensions of the 
grains and their chemical constitution also influence this 
property. The absorbing and retaining powers are not 
necessarily equal, and are greatly influenced by the degree 
of moisture; damp soils absorb heat more slowly, but they 
also cool more slowly than dry soil. 
The following table by Schubler shows the capacity of 
different soils of absorbing and retaining heat—100 being 
assumed as the standard: 
Sand with some lime, 100.0 Clayey earth, 68.4 
Pure sand, 95.6 Pure clay, 66.7 
Light clay, 76.9 Fine chalk, 61.8 
Gypsum, 72.2 Humus, 49.0 
Heavy clay, 71.1 
It will be seen, therefore, that sandy soils are warmer, 
and clayey soils are not only damp but colder. 
The degree of temperature depends entirely upon, the in- 
tensity of the sun’s rays and differs in different latitudes 
and climates; but everywhere the rays of the sun produce 
two currents of heat in the soil. One wave is diurnal, the 
heat passing down in temperate climates to about four feet 
during the day, and receding during the night; the depth 
naturally varies with the season and the nature of the soil. 9 
The other wave is annual, and in temperate climates the 
wave of summer heat reaches from fifty to one hundred feet. 
The line of uniform annual temperature, according to 
Forbes, is from fifty-seven to ninety-nine feet below the 
surface. 
5. Soil Pollution.—By soil pollution, we mean the presence 
of various impurities of vegetable or animal origin, which 
have either been washed from the surface into the soil or 
are derived from defective drains, sewers, cess-pools, privies, 
slaughter-houses, glue and soap factories, etc. Impurities, 
as already indicated, are also naturally present in alluvial 
and marshy soils. The impurities may be solid, soluble, 
and suspended or organized. Solid particles may be washed 
down as far as the pores of the soil will admit of their pen- 
etration and thence lodge, to be acted upon by the processes 
of disintegration. 
Of the soluble organic matter likely to be present in soil 
pollution, whether from leaking cess-pools, sewers, drains or 
surface-pollution, we find soluble albuminoids, urea, am- 
monia and lime phosphate. The nitrates, nitrites and chlo- 
rides are generally not absorbed by the soil. 
The suspended matter, whether living or dead, is held by 
the constituents of the soil, just as they would be arrested 
in a filter; it is for this reason that the surface of even virgin 
soil contains a large proportion of organic matter constitut- 
ing the rich loams of our country. Indeed, this accumu- 
lation may be so great, that all the pores of the surface of 
the soil are filled with debris and the filter is clogged, in 
which case the water cannot penetrate and runs off; but if 
there is a dead level or a depression, it naturally stagnates 
and forms ponds or swamps. 
The extent to which soil pollution can take place depends 
largely upon the porosity of the soil; and whilst it is gener- 
ally considered that loose porous soils are healthy because 
they are dry, we may justly add, provided no soil pollution 
has taken place. 
This I can best illustrate by the medical history of a 10 
family which had more sickness, especially the so-called 
filth diseases, than any other family in my town. The in- 
habitants of a new house were well-to-do, intelligent and 
cleanly; the well was close to the house and the privy at 
least 150 feet from the well. It was impossible to connect 
the occurrence of typhoid fever and diphtheria in this family 
with a previous case; but I was informed that the building 
site, a dry gravelly spot, was formerly used for a cow corral 
and hog pen. In view of all the circumstances, there was 
nothing improbable in the assumption that the animal 
refuse matter permeated the soil for a considerable depth 
and furnished suitable food for disease-germs, which, with 
the recession of the sub-soil water, were stimulated into 
activity, and finally percolated into the well, or gained ac- 
cess into the air of the rooms by the movements of the 
ground-air in the manner already referred to. 
But, not to digress too much, let us study the efforts of nature 
to eliminate impurities in polluted soil. It is very certain that 
the organic matter does not remain unchanged. In porous 
soils, where the air can gain free access, oxidation takes 
place. The carbon is converted into carbonic acid and the 
nitrogen into nitrates and nitrites; and this explains the 
excess of carbonic acid even in virgin soil. A certain de- 
gree of moisture is, however, necessary; for it has been 
shown that if only 1 or 2 per cent, of moisture is present, 
no carbonic acid is generated. Warmth is also essential; the 
production of C02 of nitrates and nitrites goes on quite 
rapidly in warm soils, but is retarded in cool weather, and 
ceases almost completely at the freezing point. Last, but 
not least, the presence of bacteria is absolutely essential in 
the decomposition of organic matter. Pasteur has shown 
that in soil in which these organisms have been destroyed 
(sterilized), no nitrification takes place, even if all the other 
conditions are present. From these and numerous other 
experiments, it has been concluded that the oxidation of 
organic matter in the soil is not a purely chemical process, 
but is brought about with the aid of micro-organisms, which 11 
feed upon it, and as they multiply, they split up the organic 
matter into simpler compounds. 
The rapidity of oxidation, apart from the conditions men- 
tioned, is also influenced by the chemical constitution of 
the soil; a certain degree of alkalinity is absolutely essen- 
tial. In fact, nitrification ceases when the nitric acid fails 
to find a suitable base for its combination. 
It has been shown that next to lime, the presence of soda; 
potassa and ammonia carbonate hastens nitrification. 
It will be seen that this beautiful process of nature is 
evidently intended for the purification and utilization of 
effete matter, and thus not only interests the agriculturist, 
but also the sanitarian. Nature is ever kind and indulgent* 
and it is only when we impose upon her, or expect too much 
from her forces, that we are disappointed. 
The capacity for self-purification of the soil is naturally 
limited. If the soil is charged with organic matter to a 
greater extent than it is capable of oxidizing, by reason of 
its physical and chemical constitution, an accumulation 
takes place, which naturally affects the permeability and 
healthfulness of the soil; for in place of oxidation, we will 
have deoxidation or putrefaction, all because the pores of 
the soil are closed and oxygen cannot enter. In such an 
event, we get nitrous acid and ammonia; the sulphates are 
reduced to sulphides, and we find in consequence hydrogen 
sulphide, ammonium and ferrum sulphides. If much iron 
is present, free hydrogen sulphide is not produced, no mat- 
ter how strong the organic pollution may have been ; but if 
the soil is deficient in ircn and rich in gvpsum, free sul- 
phuretted hydrogen is evolved. Even these reduction pro- 
cesses are not purely chemical, but are initiated by the bac- 
teria of putrefaction. 
The principal sources of soil-pollution may be summed 
up as follows: Human and animal refuse, faeces and urine, 
the dead bodies of animals and man, vegetable debris, 
refuse of industral pursuits, and deposits from floods. These 
are especially objectionable if the soil in the particular local- 12 
ity is already damp and likely to keep the fresh sediment 
also damp. If, on the other hand, the mud has a chance to 
dry, oxidation will speedily destroy the rich quantities of 
organic matter contained therein. 
6. Micro-Organisms in the Soil.—Reference has already 
been made to the presence of microbes in the soil. They 
are quite numerous, but decrease in number with the depth 
of the soil. 
Beumer (Deutsche Med. Wochenschrift, 1886, No. 27,) found 
in— 
1 c. c. of sandy loam at a depth of 10 ft., 44-45 million germs. 
“ “ “ “ 13 ft., 4-10 
“ “ “ “ 16 ft., 5-8 
“ “ “ “ 20 ft., 6-5 
“ “marls “ “ 13ft., 1| 
“ “ “ “ “ 16 ft., li 
“ marls “ “ 13 ft., 750,000 germs. 
“ “ “ “ 16 ft., 380,000 “ 
“ cemetery earth,sandy, “ 4 ft., 1,150.000 “ 
“ “ humus,“ 6 ft., 430,000 “ 
“ yellow clay, “ 6 ft., 260,000 “ 
The investigations of Pagliani, Maggiori and Fratrini at 
Milan, in 1887, quoted by Uffelmann, also show that the 
upper layers of the soil contain the greatest number of 
micro-organisms; that they decrease with the depth; that 
they are more numerous in manured and cultivated than 
in virgin soils, and that the soils of forests contain the least 
number of germs. 
The micro-organisms of the soil include fungi, ferment 
bodies and bacteria—the latter preponderate in the upper 
layer of soil. 
Of the fungi which have been isolated, there are, accord- 
ing to Adametz, the following varieties: Penicil. glaucum, 
mucor mucedo, M. racemosus, M. stolonifer, Asper. glaucus, 
Oidium aurantiacum, O. lactis and clostridium butyricum. 
Of the ferment bodies, the saccharomycetes glutines, cere- 
visise, and rosaceus and the Monil. cand. have been demon- 
strated. 
Of the bacteria, there have been found the micrococcus 13 
candidus, luteus, aurantiacus, versicolor, cinnabareus, rosa- 
ceus, diplococcus luteus, bacterium lineola, termo, subtilis, 
mycoides, viridis, liquifaciens and non-liquifaciens; B. alius, 
rubescens, prodigiosus, proteus vulgaris, the baccilus buty- 
ricus, vibrio rugula and many others. 
Of the pathogenic bacteria, the following have so far been 
discovered in the soil: The bacillus of tetanus by Nicolaier 
in garden earth, but it is not found in all soils. Bonome 
claims to have found this bacillus also in mortar, in which 
case it was probably derived from the soil. The bacillus of 
anthrax was found by Frank in the clay of a stable formerly 
kept for the storage of Ir’des. The bacillus of malignant 
oedema was found by Koch and others, and the bacillus 
typhosus by Tryde in the soil beneath a barracks. Ivlebs 
and Tommasi-Crudeli described a bacillus found by them in 
the water and soil of the Roman Campagna, which they 
regarded as the microbe concerned in the causation of mala- 
rial fevers; but it is now held that Laveran’s plasmodium 
malarise (a species of protozoa) is the essential agent of the 
disease. 
The investigations, so far, appear to indicate that patho- 
genic microbes are not very frequent in the soil. On the 
other hand, it must be remembered that the methods of 
bacteriology are far from perfect, and that much more may 
be accomplished in future. 
The development of the micro-organisms naturally de- 
pends upon a suitable food, moisture and a certain degree 
of warmth. This pabulum they find in the organic matter 
of the soil, which not only contains carbon and nitrogen, 
but also the salts requisite for their growth. Investigation 
has shown that when the soil contains less than 4 per cent, 
of moisture and possesses a lower temperature than 32°, 
their development ceases, and that they luxuriate best in a 
warm porous soil rich in organic matter, moist but not wet, 
and they nearly all require a sufficient amount of oxygen. 
In order to determine the depth at which pathogenic 
bacteria may still grow, Frankel made a series of experi- 14 
ments with anthrax, typhoid and cholera bacilli, and found 
that the multiplication of anthrax bacilli is retarded at a 
depth of seven feet, and completely arrested at ten feet; 
the bacilli of cholera continued to grow at a depth of ten 
feet during the months of August, September, and October, 
but not during the other months; at a depth of five feet, 
however, proliferation continued during the entire year. 
The typhoid germs ceased to grow, at a depth of ten feet, 
only during the months of April, May, and June; during 
all other months of the year, they multiplied vigorously. 
Whilst the number of micro-organisms in the soil is 
really enormous, by far the majority are harmless, and are the 
scavengers of nature and ever active in the nitrification, fer- 
mentation, and putrefaction, which split up the organic mat- 
ter into substances best suited for assimilation by vegetable 
roots. It is perfectly conceivable, that disease germs may 
be washed from the air or gain access to the soil by clinging 
to organic matter of every description, and thus find their 
way into wells and springs, or they may reach the surface 
by the ascending currents of the ground-air, and be again 
liberated from the pulverized soil. Pasteur has pointed out 
how anthrax bacilli have been turned up by earth-worms, 
and it is scarcely necessary to indicate the many wTays by 
which man himself, in excavations and agricultural pur- 
suits, may be instrumental in bringing the microbes to the 
surface. The occurrence of malarial fevers, after turning 
up the sod of virgin soil, can rationally be explained in this 
way. 
Summary.—From the foregoing, it is evident that the soil 
may affect the health of those immediately residing thereon 
by the ground-air, dampness, soil pollution, and disease- 
germs. 
We have seen that the ground-air is in constant motion, 
interchangeable with the atmosphere and the air of our 
houses—that it contains impurities, viz: an excess of car- 
bonic acid, sometimes ammonia, and occasionally hydrogen 
sulphide, and coal gas. If these gases pass directly into the 15 
atmosphere, no harm can result; if they pass into our cellars 
or basements, the air of our homes will be vitiated. The 
extent to which this may take place we cannot here discuss. 
The possibility of disease germs entering the outer air and 
the air of habitations through the movements of the ground- 
air has also been pointed out. 
In reference to the moisture of soils, we have learned that 
the degree of moisture naturally affects the humidity of the 
atmosphere; it is for this reason that the air of meadows 
and valleys is, generally speaking, damper than the air over 
sandy plains or agricultural soils. The humidity of the soil 
is of the greatest importance in the disintegration of organic 
matter, and may determine, in one instance, oxidation—in 
another, reduction or putrefaction. The degree of moisture 
may be just sufficient to promote or arrest the development 
of certain disease germs. The rain which percolates the 
soil may carry these germs into the ground-water and thus 
contaminate the drinking water, provided, of course, they 
have not previously been arrested by the filtering and ab- 
sorbing properties of the soil. 
In regard to the ground-water, we have seen that its rise 
and fall influences the amount of moisture in the upper 
layers; if it rises to within a few feet of the surface, the 
dampness extends by capillary attraction to the atmosphere, 
and by evaporation cools the air; and if, perchance, a dwell- 
ing should be located on a damp soil, this dampness will 
extend to the house, and may cause a damp and chilly air 
within. 
The movements of the ground-water also cause corres- 
ponding movements of the ground-air; a sudden and con- 
siderable rise of the ground-water forces the ground-air be- 
fore it and out of the soil. This may result in an upward 
displacement, not only of noxious gases and effluvia, but 
also of micro-organisms. I have had repeated opportuni- 
ties to observe the disagreeable effluvia, after a sharp ri«e of 
the stream which drains this town. A gradual rise accom- 
plishes, of course, the same purpose. With a recession of 16 
the ground-water, the air enters the deeper layers of the 
soil, and may stimulate into activity certain disease germs 
which remained dormant as long as they were submerged. 
In reference to soil pollution, it is evident that even the 
manuring of cultivated fields may give rise to offensive 
effluvia; it is an open question whether such emanations 
can produce disease, or whether the presence of organic 
matter in the soil is ever itself the cause of disease. It is 
probable, however, that it simply furnishes a vehicle and 
suitable nutriment for disease germs, since we know that soil 
pollution plays an important rc>le in the production of ty: 
phoid fever, malaria, diphtheria, dysentery, and other filth 
diseases. 
We know that pathogenic germs may be conveyed from 
the soil directly and indirectly. The investigations of Bo- 
nome, Beumer, and others, have shown that contact of open 
wounds with certain soils has resulted in trismus and teta- 
nus, and the same mode of infection is probable in malig- 
nant oedema, which is also caused by a specific germ. Gen- 
erally speaking, however, disease germs first gain access into 
the air or water. It has been indicated how they may reach 
the air in the form of pulverized dust and be inhaled; other 
germs may reach the water-courses or percolate into wells 
and springs through the movements of ground-water. 
We also know that cattle which have been grazing on grass 
and clover-fields, the soil of which has been infected by 
burial of dead animals from anthrax, have contracted the 
disease. This at least suggests the possibility that the 
germs of typhoid, dysentery, etc., may be conveyed from 
fields, through the medium of vegetables which are eaten 
raw, like lettuce, radishes, strawberries, etc. By examining 
these, after a heavy shower, and observing the spattered 
mud, we can readily appreciate how such a transmission is 
possible. 
The Relations of Soils to Certain Diseases.—Whilst it will 
be impossible to consider here, in all its details, the influ- 
ence of soil in the production of diseases, we shall enumer- 17 
ate a few of the most prominent affections believed to be 
intimately connected with the constitution of certain soils: 
(1) Endemic Goitre and Cretinism.—According to Bireher’s 
investigations, these affections occur solely in localities where 
the soil and geological formations are composed of marine 
deposits of the Palaozoic age—the trias and tertiary period. 
The eruptive formations, the crystallized rocks of the an- 
cient formation, the sediments of tura and chalk, as well as 
those of the quarternary period, and all sweet-water depos- 
its, are believed to be free from the disease-producing agent, 
which Bircher believes to be the “ navicula,” a form of the 
algre, which occurs in the drinking water of these marine 
deposits. 
Kratter, however, found that alpine cretinism was most 
prevalent in localities where the soil consisted of the debris 
of primitive rocks, and the springs had their origin in such 
formations that it was rarely seen in limestone regions, that 
it was not observed in altitudes above 3,400 feet, nor below 
those of a 1,000 feet, and that it was most frequent in alti- 
tudes between 1,400 and 2,300 feet. 
It was formerly believed that these diseases were con- 
nected with limestone formations, but, in the mountains of 
Tyrol it occurs muchoftener in slate districts, and the lime- 
stone regions of England and France afford comparatively 
few cases. Some authors attribute the cause to magnesian- 
limestone deposits, and Klebs disclaims the influence of soil 
formations on these affections altogether. The evidence is 
quite conflicting, but it is very certain that goitrous and 
cretinic districts exist, and there are numerous well-attested 
cases of healthy women living during their pregnancy in 
such districts, bringing forth cretinoid children, who, re- 
moving from such localities, propagate healthy children.— 
[Down.~\ 
(2) Malaria.—It has not yet been definitely settled 
whether Klebs’ bacillus or Laveran’s plasmodium malarise 
is the etiological factor of malarial diseases. Both organ- 
isms are believed to have their habitat in malarial soils. 18 
Whilst it is impossible to give the exact composition of the 
soil requisite for the development of malaria, we know that 
it requires a soil rich in organic matter—moist, but subject 
i,o periodical dryness. Such soils are principally found in 
valleys or on plains, with depressions favoring the stagna- 
tion of water and formation of marshes; also in localities 
subject to periodical overflows, especially near the sea-coast, 
where a mixture of sweet and salt water results in the so- 
called brackish water. Endemic malaria is not observed in 
dry, well-drained soils, especially when poor in organic 
matter. Another important factor is a certain degree of 
heat. Tommasi-Crudeli demonstrated that his bacillus only 
matured at a temperature of 36° and above; the inference 
is that soils possessing a lower temperature than 36° cannot 
produce the germs, and our knowledge of the geographical 
distribution of malaria confirms this. The disease is very 
infrequent in the northern part of the United States; it is a 
rarity in the Faroean Islands, and unknown further north, 
whilst it increases as we travel south, and amounts to al- 
most a scourge in sub-tropical and tropical climates. As a 
periodical drying of the soil is one of the factors necessary 
for the diffusion of the malaria, it may be claimed that this 
process liberates the microbes; which are held down as long 
as the soil is moist. But this is not applicable in all cases, 
for we know that malarial intoxication often follows large 
■excavating operations before the soil even had an opportu- 
nity of becoming pulverized. 
The good effects of drainage in reducing malarial affec- 
tions almost 75 per cent, have been demonstrated in Michi- 
gan, and similar results have been obtained in Italy, France, 
Algiers, England, and Germany. 
The withdrawal of moisture, and consequent change of 
environments, evidently prevents the propagation of the 
germs, as the disappearance or diminution of the disease 
resulted from proper drainage. 
(3) Dysentery.—Clinical experience points to the fact that 
dysentery is most prevalent in malarious regions. Wasser* 19 
fuhr attributes the virus of dysentery to a moist, warm soil, 
charged with organic matter and polluted with animal ex- 
creta ; he refers to a locality in Alsace used for an artillery 
drill-ground, which not only affords numerous cases of dys- 
entery, but also of malarial fevers and intermittent neural- 
gia. The soil is peaty, resting on a layer of sand which is 
upheld by a deposit of dense clay. Prof. Virchow, however, 
tells us that dysentery occurs in localities which are quite 
free from malaria, as in certain parts of Egypt, where its 
prevalence is solely attributed to impure drinking wrater. 
It is quite probable that soil-pollution added to a malarious 
soil, especially in overcrowded camps, favors the develop- 
ment of the virus of dysentery, which finally enters the sys- 
tem in the form of amceb* through contaminated drinking 
water. 
(4) Tuberculosis.—The relations between dampness of soil 
and pulmonary consumption were first pointed out by Dr. 
Bowditch, of Boston, and Dr. Geo. Buchanan, of England, 
and the facts compel a fair investigation. Dr. Buchanan, 
in the Ninth Report of the Medical Officer of the Privy 
Council, London, 1867, also supplies ample statistical proof 
that consumption became less frequent in certain towns 
after they had been sewered and the soil consequently 
drained. In some towns, where the drainage was perfect, 
the deaths from phthisis were reduced by a third, or even 
by half. \ 
Mortality from, Consumption 
Before Sewers. 
After Sewers. 
Decrease. 
Merthyr, 
38.G6 
34.33 
4.33 
Bristol, 
31.00 
25.50 
5.50 
Leicester, 
43.33 
29.25 
14.08 
Cheltenham, 
28.75 
21.25 
7.50 
Cardiff, 
34.75 
28.66 
6.09 
Macclesfield, 
51.50 
35.60 
15.90 
Newport, 
37.00 
25.00 
12.00 
Warwick, 
40.00 
32.33 
7.67 
Banbury, 
20.66 
15.66 
11.00 
Salisbury, 
44.33 
22.66 
21.67 
Ely, 
31.00 
16.75 
14.25 
Worthing, 
30.50 
19.50 
11.00 
Rugby, 
28.50 
16.25 
12.25 20 
It is true that a reduction in mortality did not always fol- 
low the introduction of sewers, but in such instances it may 
be fairly assumed that the soil was previously quite dry, 
and could not be affected by increased drainage. 
Uffelmann refers to a striking illustration of damp habi- 
tations as a predisposing cause to consumption. It is a 
prison near Vienna containing on an average 200 inmates. 
Every convict is examined before his transport, and if 
found affected with incipient phthisis, he is sent elsewhere. 
In spite of this precaution, the deaths number about fifty 
per annum, and the majority die from consumption. The 
prisoners are better fed in this institution than elsewhere, 
but the building rests on a damp, clayey soil, the walls are 
reeking with moisture, and the rooms smell musty. 
The relation of dampness to consumption can only be 
explained on the ground that the bacilli of tuberculosis 
luxuriate best in such an atmosphere, which, on account of 
its humidity, very likely contains also much organic mat- 
ter. Apart from this, a damp air naturally predispi S3S to 
catarrhal affections, and these, in turn, render the mucous 
membrane more vulnerable to the invasion of the tubercle 
bacilli. 
(5) Enteric Fever and Cholera.—There is considerable dif- 
ference of opinion on the influence of soil as a factor in the 
causation of these diseases. Prof. Pettenkoffer and his ad- 
herents believe that the soil is absolutely essential in the 
spread of these diseases; that the virus develops in the soil 
and is carried by emanations into the air, and that the rise 
and fall of the ground-water determines the frequency of 
these diseases. He holds that a fall of the subsoil water is 
followed by an increase, and a rise of this water by a de- 
crease in the number of cases. The majority of sanitarians 
of the present day assume, however, that the virus of ty- 
phoid fever and cholera is reproduced in the body of those 
afflicted with the disease; that it requires no further elabo- 
ration or maturity; that this virus leaves the body in the 
excretions and is capable of proliferation wherever it finds 21 
suitable environments; they look upon certain articles of 
food, as well as certain waters and soils, especially those 
contaminated with organic matter, as suitable media for 
the multiplication of these germs. According to this view, 
the soil is simply the medium for the propagation of these 
germs and their transference into the drinking water; and 
whilst the rise and fall of the ground-water doubtless facil- 
itates their passage into springs and wells, it plays another 
rdle in so far as it affects the amount of air, heat and mois- 
ture requisite for the multiplication of these germs. 
(6) Cerebro-Spmal Meningitis.—Clinical experience points 
to the fact that this disease occurs most frequently in damp 
and polluted localities. In the numerous epidemics which 
have been studied, the habitations were found almost inva- 
riably damp, the soil polluted, and in many instances the 
outbreak followed floods or inundations. 
iSanitary Measures in Reference to Soil.—From the forego- 
ing remarks, it is evident that the principal sources of dan- 
ger from soil are dampness and soil-pollution. 
The relations of dampness to the more important diseases 
like malaria, dysentery, consumption, etc., has been pointed 
out, and we might have included pneumonia, rheumatism, 
neuralgia, and many other diseases in which dampness con- 
stitutes a predisposing factor. 
We have learned the necessity of excluding the ground- 
air from our houses by cementing the basements; and as 
the dampness of the soil not only affects the atmosphere, 
but, by capillary attraction, extends to our houses the ne- 
cessity for rendering the walls damp-proof, by a course of 
slates imbedded in cement above the level of the ground, is 
obvious. These are matters more strictly belonging to the 
hygiene of habitations, and we will therefore consider the 
means at our command to render damp soils dry. The 
good effects of drainage have already been pointed out; 
this should be done wherever the moisture is excessive and 
another outlet for the water cannot be secured. In many 
localities surface-drainage appears to answer the purpose, 22 
but sub-drainage is of the greatest value in influencing the 
height of ground-water, which is carried off when the water 
rises to the level of the drains. Some localities have been 
rendered more salubrious by planting trees, which absorb a 
great amount of moisture and give it off in evaporation. 
It has been estimated that an oak tree evaporates 8J 
times the rainfall, and the eucalyptus absorbs and evapo- 
rates eleven times the rainfall over the area it covers. This 
tree has been extensively planted in malarious districts with 
the effect of diminishing malaria. It is quite possible that, 
apart from its value in diminishing the moisture of the 
soil, the ethereal oil 6f eucalyptus being a germicide, may 
exert its properties on the microbe of malaria; but, on the 
whole, there is nothing like perfect drainage, especially in 
marshy soils, for it has been shown that vegetation alone is 
insufficient to render the Campagna di Roma salubrious. 
Measures looking to the prevention of soil-pollution con- 
sist in the proper care and disposal of refuse, more espe- 
cially the animal excrementitious matter, and the construc- 
tion of proper sewage systems. Apart from this, much may 
be done in communities by pavements, grading and seeding 
of the soil in public places. 
The effects of floods may be mitigated at least by 
promptly cleaning out the wells and springs, and the re- 
moval of surface deposits as far as this is possible. Under 
no circumstances should the water in overflowed districts be 
allowed to stagnate. 
Distribution and Comparative Ilealthfulness of American 
Soils.—The most widespread soils in the United States are 
sandy soils, clayey soils, and loams The sandy soils consist 
of about 75 per cent, of quartz-sand, and are generally the 
healthiest on account of their warmth and dryness, provi- 
ded, however, they have not been subjected to soil-pollution,, 
and are not kept damp by an underlying layer of clay or 
other impermeable strata. 
(2) The clayey soils contain 75 per cent, or more of clay,, 
[alumina silicates], and are objectionable for building sites, 23 
because they are usually cohl, wet, and impermeable, unless 
the surface affords good drainage, or the site is sub-drained. 
The loamy soils are sub-divided into sandy or clayey loams, 
according as one or the other of these constituents predom- 
inates. The clayey loams should be avoided, and whilst 
clean dry sandy loams are usually healthful, they may, like 
the sandy soils, present similar objections. 
In addition to the soils referred to, we find the following 
less frequent: The stony or gravelly soils, which are quite lo- 
cal in distribution, and generally very desirable for build- 
ing sites, on account of their warmth and dryness. The 
calcareous soils are loams or sands impregnated with 5 to 50 
per cent, of carbonate of lime, and occur only in limestone 
or marble districts. Apart from the hardness of the water, 
which in itself is not injurious, the soil is generally regarded 
as salubrious. Magnesian soils result from the disintegration 
of serpentines, talcose, or other magnesian rocks—they are 
porous soils, and usually healthy; the magnesian salts in 
the water supply are objectionable, but these soils are quite 
uncommon in this country. The highly ferruginous soils are 
very local, and overlie deposits of log iron ore. Malarial 
diseases have been attributed to their proximity, but Dr. 
Britton has heard no such complaints in this country. The 
mud and pent soils are confined to low grounds or mountain 
valleys, which afford no outlet for the surface water; they 
are essentially marsh soils, consisting of loams or clays sat- 
urated with water and charged with vegetable matter to the 
extent of 50 per cent, and over. Whilst peat soils are non- 
malarial, they should be avoided. The soils of humus and 
mold result from abundant vegetation in comparatively dry 
localities, and are the natural soil of forests and former 
prairies covered with grasses and herbs, and rarely extend 
beyond a foot in depth. 
Soils are either indigenous or transported; in the latter in- 
stance, they have been brought by glacial action or the 
forces of water from other localities, and may have nothing 
in common with the underlying rocks. 24 
The soils of glacial drift consist of deposits of clay, sand, 
gravel, and boulders, which have been brought from the 
north in icebergs during the glacial epoch; sometimes there 
are signs of stratification, but generally there is an absence 
of structure. The surface of glacial drifts is usually irreg- 
ular and affords good drainage, but at times an excess of 
clay renders them less desirable for building sites unless 
properly drained. Along the southern margin of this drift, 
on the Atlantic Coast, the surface conformation of the “ter- 
minal moraine ” is such as to favor the formation of swamps 
and stagnant ponds in hollows, often surrounded by much 
higher grounds, although many feet above tide-level. In 
such instances, proper drainage affords the only remedy. 
The drifts in some localities present a well-marked strati- 
fied structure; this may have been the result of direct gla- 
cial action, but more often the clay, sand, and gravel, were 
deposited trom the currents of water and lakes which ac- 
companied the melting of the glaciers. When these drifts 
are mostly composed of sand and gravel, the soil, on account 
of its porosity, decline of surface, and freedom from organic 
matter, is very salubrious, but an excess of day renders 
them suspicious. The so-called yellow drift is found ex- 
tending in patches from the southern coast of New England 
over nearly the whole of Long Island ; thence southerly, 
composing nearly all of the soils of Southern New Jersey, 
Delaware, Eastern Virginia, and in patches along the coast 
of Florida. Much of this territory is covered by pine for- 
ests, and the majority of our seashore and health resorts are 
situated in this belt, which owes its salubrity to the sandy 
and gravelly nature of the soil. These yellow drift depos- 
its are believed to have been made before the glacial drifts, 
at a time when a large part of Eastern North America was 
still submerged. 
Alluvial deposits are the result of the action of water in 
depositing the silt held in suspension, and when only 
slightly elevated above the level of the stream usually oon- 
tain a dangerous amount of organic matter. River terraces 25 
are produced by a stream cutting through such deposits to 
gain a lower level, and by these the ancient course of a 
stream may often he traced. Lake terraces generally indi- 
cate the former levels of the water; the highest benches are 
always preferable for building sites, but the river terraces 
contain generally more or less clay. Marsh soils are often 
found in deltas the result of river deposits; but for reasons 
already given, indigenous soils may become swampy; they 
are found almost in all sections, but most frequently along 
the Gulf and the Coast of the Atlantic; the largest in the 
United States are the Dismal Swamp of Virginia, and the 
Everglades in Florida. Brackish swamps are commonly 
called salt meadows. There are very few peat deposits in 
the United States, but they are quite frequent in Newfound- 
land, Great Britain, and Germany; the non malarious char- 
acter of peat soils has been justly attributed by Dr. Britton 
to the antiseptic action of organic acids contained therein. 
The marine alluvium forming our salt-meadows, though not 
malarial, are objectionable, on account of their dampness 
and liability to overflow. A large portion of the far West 
is covered by alkaline plains. The soil is generally a light 
loam, sometimes clayey or sandy, containing very little or- 
ganic matter, but an excess of sulphates, carbonates, or 
chlorides of soda, potash, magnesia, and lime. These salts 
render the waters intensely purgative and dyspeptic, and 
renal affections are quite common. The soils are otherwise 
healthy, provided no pollution has taken place; the clouds 
-of alkaline dust are very objectionable, and catarrhal dis- 
eases and eye-troubles are frequently seen. The soils pre- 
dominate in Idaho, Utah, Wyoming, Nevada, Arizona, and 
New Mexico; the great basin or arid region formerly cov- 
ered with an inland sea, and of which the great Salt Lake 
and a number of smaller alkaline lakes still remain. At 
present, this section is only sparsely settled on account of 
the scarcity of water; all of the arable land near the mouth 
of canons, and along the mountain streams, has been taken 
up, however. My observation in this section teaches me 26 
that the well water is almost unfit fur domestic purposes, 
but the springs and artesian wells furnish a supply of good 
quality. 
The seashore sands are too well known for their salubrity 
to require further comment. Reference has already been 
made to the objections of so-called “ made ground,” and we 
need hardly repeat that deep lots should never be made the 
dumping-ground of waste matter and rubbish mingled with 
dirt, nor is it necessary to insist that a swampy place cannot 
be made dry by a deposit of even good soil. Whilst proper 
grading is very desirable in the construction of streets and 
the preparation of building sites, the depressions should 
never be filled up until they are thoroughly drained, and 
then only with pure soil. 
Having briefly considered the general characteristics of 
soil which have been transported to their present resting- 
places by the forces of nature or the hand of man, reference 
should be made to the indigenous soils, so-called, because 
they result from the disintegration of the local rock forma- 
tions. These soils predominate in the non-glaciated parts 
of the country, where they form most of the superficial ac- 
cumulations, also wherever the glacial drift is thin or want- 
ing. A heavy deposit of this drift naturally obstructs the 
action of the elements upon the indigenous rock formation. 
To this class of soils belong those derived from granite* 
gneiss, trap, porphyry, and feldspathic rocks generally, 
yielding either stiff or loose clays or loams. A true sandy 
soil is rarely produced from such rocks, and they are not 
specially salubrious unless rendered so by perfect natural 
surface-drainage. 
These soils are found in patches on the eastern slope of 
the Appalachian range, especially in Western New Jersey 
southward; they are generally found in hilly or mountain- 
ous regions—in certain parts of the Rocky Mountains, the 
Sierras, and other western ranges. 
The soils derived from slates or shales are often clayey, and 
therefore objectionable, unless the strata are sufficiently 27 
tilted. Such soils are freely met with along the southern 
and middle portions of the Appalachian range, in the 
Southern and Central States, and in the far West. The sa- 
lubrity of sandy soils has already been pointed out, and this 
is especially the case when the sandy loams have been 
formed by the disintegration of the rock, and therefore less 
contaminated with other alluvial deposits. These soils are 
very common in the United States south of the glacial drift. 
The soils derived from indigenous limestone and marble 
are also quite common in this country, and have already 
been referred to. 
[For further details, see Parke’s Hygiene, American Ad- 
ditions, from which the foregoing has been condensed.] 
Examination of the Soil.—A complete sanitary investiga- 
tion should include the following points, viz: 
(1) The configuration of the locality, height above the sea 
level, angle of declivity, facilities for natural drainage, wa- 
ter-sheds and courses, covering of soil by trees, brushwood, 
and grasses. 
(2) Geological formation, dip and character of strata, es- 
pecially in reference to their permeability. 
(3) Examination into the size of the fragments or grains 
composing the soil is readily conducted by means of grad- 
uated sieves and a low power of the microscope. 
(4) The porosity of the soil is usually determined by tak- 
ing a liter of kiln-dried soil and ascertain how much water 
is taken up. The water must be added until air-bubbles 
cease to form. This is a simple, but not the most exact 
method. 
(5) The moisture of the soil is determined by weighing a 
certain quantity; it is then exposed to a temperature of 220° 
until dry, and weighed again; the difference is water or some 
volatile substance. 
(0) The capacity of the soil for holding water is ascertained 
by thoroughly wetting a certain quantity previously weighed, 
drain off the water, and weigh again. This is not a precise 
method. 28 
(7) Measurement of the Ground-Water.—The height of the 
water-level in wells is the best indication of the height of 
the ground-water. Pettenkoffer uses a rod for shallow wells 
and a cord for deep wells, to which are attached a number 
of little cups, which are let down into the well and drawn 
up again; the uppermost cup containing water, marks, of 
course, the height of the water, the length of this measure 
being known, the changing level of the well can be estima- 
ted to within one-half inch. Some precautions are neces- 
sary; for if a rope is used, it may stretch after prolonged 
use or during a hot wind, or shrink in wet weather, and 
thereby render the observations inaccurate, but not suffi- 
ciently so for practical purposes. It is best to use a rod in 
shallow wells, and the measurement should be made at a 
time when the supply has not been lowered by unusual con- 
sumption. 
(8) The ground air is examined by sinking a shaft about 
sixteen feet deep, into which are placed lead pipes in 1?, 
feet, three feet, seven feet, nine feet, and fifteen feet lengths, 
and one-half inch in diameter. The soil is put back as 
nearly as possible into the original levels. The lead pipes 
are connected with an aspirator by means of rubber-tubing, 
and the aspirated air is examined for the determination of 
oxygen, carbonic acid, ammonia, hydrogen sulphide, and 
organic matter. The movements of the ground-air are deter- 
mined by differential manometers. 
(9) Soil-pollution is determined by a chemical analysis for 
the estimation of nitrogen and carbon. A simple way to 
ascertain the percentage of volatile matter is to take ten 
grammes of dried pulverized soil, incinerate at a red heat, 
recarbonate with carbonic acid solution or ammonia car- 
bonate; heat again to expel excess of ammonia and weigh. 
The loss represents the amount of organic matter. The per- 
manganate process is also applicable. 
(10) The micro-organisms of the soil are best determined 
by using a borer invented by Frankel, and constructed on 
the principle of a butter-tester. This borer must be steril- 29 
ized, and can be inserted to any desired depth. Upon with- 
drawal of the instrument, Friinkel measures off, by means 
of a sterilized platinum spoon, a given quantity of the soil, 
and places it in a nutrient gelatine-culture tube, and shakes 
the mixture well. A small quantity of this is placed on 
glass plates under a damp glass air-chamber; and after the 
formation of the colonies, they are counted and isolated in 
the usual manner. The platinum measures hold about two 
grains of soil, as a larger amount Would render the culture 
experiment very difficult and confusing because of the num- 
ber of micro-organisms present. 
(11) The temperature of the soil can be readily determined 
at any desired depth by placing a self-registering thermom- 
eter, properly protected, in a “drive well point joint.”