ARTICLE IX. 
Observations of the Magnetic Intensity at twenty-one Stations in Europe. By 
A. D. Bache, LL. D., President of the Girard College for Orphans, one of the 
Secretaries of the American Philosophical Society, fyc., §c. Read March 6, 
1840. 
The following observations of intensity and dip were made during a visit to 
Europe in 1836-7 and 1837-8, directed by the Trustees of the Girard College 
for Orphans. The special objects of my journey admitted of only an occasional 
attention to the observations in question, which I did not attempt unless when 
time and circumstances were generally favourable to their execution. The 
stations are twenty-one in number; three in Great Britain, and the others on 
the continent. At some of the places the magnetic elements are so well known 
from numerous observations that my results can add but little to the informa- 
tion already before the public; at others, few observations have been made, and 
my determinations assume a higher relative importance. Those of the former 
class will serve, by their accordance with the results of other observers, to give 
a general confidence in the results of the latter, and will especially assist in 
connecting the European stations with those in the United States, which formed 
one principal object of experiments, the results of which I propose to commu- 
nicate to the society in a separate memoir. 
At all the places but three the horizontal intensity and dip were observed, 
and at two the total intensities were, in addition, compared by the statical me- 
thod of Professor Lloyd. The observations for the horizontal intensity were 
made by oscillating horizontal needles in a rarefied medium, in the manner ex- 76 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
plained in a former paper, read before the society.* The dip was determined 
with a six inch dipping circle by Robinson, which yielded quite as satisfactory 
results as the instrument by Gambey, used in my observations in the United 
States.f The needles for the statical method of Professor Lloyd were also by 
Robinson.J 
Two needles were ordinarily used in the observations for horizontal intensity, 
a cylinder of the Hansteen model and a bar, designated respectively as C and 
A in the memoir on horizontal intensity just referred to. The correction for 
temperature, and also, in general, the mode of observing there recorded were 
employed. To determine the time of beginning and ending of the oscillations, 
however, five sets of observations were taken, §> and the usual mode of deducing 
the mean, by comparing the five corresponding observations at the commence- 
ment and close of each series, was adopted. A pocket chronometer, by French, 
was used to observe the duration of the oscillations, and its rate during the ob- 
servations was ascertained by comparison with an observatory clock, when such 
means was at hand. This watch had been selected in reference to its quality 
of bearing change of position without considerable change of rate, and stood the 
trial to which it was exposed reasonably well. It is my impression, however, 
that when more perfect instrumental means are used in the determinations, 
greater care will be required in regard to those for ascertaining the time. The 
observed correction for the rate of the chronometer is duly applied in the tables 
of results. As all the observations were made between the same arcs of vibra- 
tion, a reduction to indefinitely small arcs is not required. || The correction for 
* American Philosophical Society’s Transactions, vol. v., N. S., Art. xviii. 
t Ibid. Art. viii. 
X They had been heated in boiling water, to discharge as much of the magnetism as could he 
done by this temperature, according to the recommendation of Mr. Christie. I supposed, from 
the result of calculations made while in Paris, that these needles lost their magnetism rapidly, but, 
on farther examination, find that such was not the case, and that they lost but a small portion of 
their force during more than a year, as will be found stated in a subsequent part of this paper. 
§ Besides eliminating errors of observation, this has the farther advantage of correcting errors of 
division of the dial plate, as noticed by Professor Forbes, in his “ Account of some Experiments 
made in different Parts of Europe on Terrestrial Magnetic Intensity,” &c., &c. Edinburgh 
Transactions, vol. xiv., part I., p. 5. 
U The semi-arcs of vibration for the cylinders were from 6° to 2°, and for the bar, from 4° to 2°. AT TWENTY-ONE STATIONS IN EUROPE. 
77 
the loss of magnetism by the needle is so fully made out, that I believe the re- 
sults to be as free from error, on this score, as if no loss had appeared from 
observation. The time of oscillation of the bar (A) was observed at Philadel- 
phia in October, 1835; again in September, 1836, just before I set out from 
home; and in December, 1838, after my return: it was observed in the inter- 
mediate time at London, in June, 1837, and again in August, 1838; at Paris 
in August, 1837, and in July, 1838. A curve was traced on a large scale by 
the results thus obtained, the ordinates representing the relative forces of the 
needle corresponding to the intervals of time from October, 1835, measured by 
the abscissae. A regular curve being traced, departed very little from the points 
obtained by observation, the differences between the ordinates of the mean 
curve and those given by the particular observations being, in terms of the ori- 
ginal force of the needle, 0.000, — 0.0005, + 0.0030, + 0.0034, and — 0.0031. 
As these individual results must be affected by small errors of observation, there 
can be no doubt of the satisfactory correction for loss of magnetism by using 
the ordinates of the curve, and, accordingly, the correction thus obtained is ap- 
plied to the results, and is entered in the tables. This needle shows a tendency 
towards a permanent magnetic state, and its loss is less than half that of the 
other. The diminution of force of the cylindrical needle, (B,) since Septem- 
ber, 1835, has been nearly uniform, and, accordingly, the curve representing it 
differs but little from a straight line. The observations used to trace this curve 
were obtained at Philadelphia in September, 1835, in September 1836, and in 
December, 1838; and in addition at the same times and places as stated in 
reference to the other needle. Although the correction for loss of force is so 
much greater for this needle than for the bar, there is no reason to suppose, 
from a comparison of their results, that this correction is not quite as well as- 
certained as the former. The differences between the observed losses of force 
and those given by the ordinates of the curve are, 0.0000, 0.0000, + 0.0035, 
+ 0.0051, and — 0.0042. The time of oscillation of this needle was farther 
satisfactorily observed at Florence, before passing into lower Italy, and again in 
returning to upper Italy; but while the general accordance of the results was 
such as to show that the force had undergone no irregular change which was ap- 
preciable, the time which had elapsed between the two observations was too short 
to justify their use in the numerical determination of the loss of magnetism by 
the needle. I have had no cause to suspect irregular changes in either of the 
VII. U 78 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
needles since they came into my possession. The needles were always kept 
separate from each other; while travelling, they were carried about my person, 
and, when stopping for any considerable length of time, were deposited as far 
from iron as was necessary to their safety. From the experiments made with 
these needles, both of which have been magnetised several years, and which 
have been kept carefully for more than six years, I should be disposed, in fu- 
ture, to adopt the plan of procuring needles of as nearly equal force as possible,* 
and keeping them in pairs, which renders them much more convenient to 
carry. It is certain that permanence of force has not resulted, in these nee- 
dles, from the opposite plan, and that the labour of observation and calculation 
are much increased by the necessity of ascertaining and applying a correction 
for the loss. In comparing two sets of experiments at a distant date, to ascer- 
tain the loss of magnetism by the needle, the results are affected by the change 
of dip which has taken place in the interval, and as it is not probable that this 
change is produced by an alteration in the total intensity, a correction is to be 
applied, which, however, except in the longest interval of my series, was 
scarcely appreciable. 
The magnetic dip was observed in the usual way, the poles of the needles 
being reversed in each series. The bar magnets for reversing the poles were 
placed in the top of the box containing the dipping circle, each pair of opposite 
poles being connected by a keeper. Notwithstanding this arrangement, the 
bars lost much of their strength, probably from the percussion resulting from a 
slight play which was allowed in the bed where they were placed; and, on my 
arrival at Berlin, their magnetism was so much diminished that the dipping- 
needles could no longer be charged by them to saturation. Since that time I 
have always taken the precaution, after changing the poles, to oscillate the 
needles within determinate arcs, and when resting on the agate planes, to ascer- 
tain, by the time of oscillation, that thejr are charged at least nearly to satura- 
tion. The statement of this precaution may be of service to others, since, with 
a diminished force in the needles, the liability to take up some other position 
than that corresponding to the true dip is increased, and the error cannot, ne- 
cessarily, be detected by discrepancies in the several readings. Of the two 
* The importance of attending to these conditions appears very strikingly from the experiments 
of Mr. Airy, with large magnetic bars. Royal Society’s Transactions, Part I., for 1839, pp. 196, 
197. AT TWENTY-ONE STATIONS IN EUROPE. 
79 
needles accompanying the dipping circle, No. 2 did not give uniformly as ac- 
cordant results as No. 1; but, in cases where differences appeared, I endea- 
voured, by increasing the number of observations, to reduce the amount of pro- 
bable error. 
In presenting these results to the society, I have concluded to give the ob- 
servations at each place, in general, separately, rather than to tabulate, at once, 
the whole series; this will enable me more readily to make such remarks as 
may be necessary, and also to compare the results with those of other observers, 
as far as I am acquainted with them, which will make the paper more com- 
plete than if I had confined it merely to my own conclusions.* 
The observations will be given in the following order:—Those at Dublin, 
Edinburgh, London, Paris, Brussels, Berlin, Vienna, Trieste, Venice, Rome, 
Naples, Florence, Milan, Turin, Chamberi, Lyons, Chamouni, the Flegiere, 
Genera, Brientz, and the Faulhorn. 
DUBLIN. 
The observations at Dublin were made in the Provost’s garden. They in- 
cluded only the horizontal intensity, as I was not at this time provided with a 
dipping-needle. The horizontal intensity is compared with that at London by 
observations made in July, 1837. 
Observations for Horizontal Intensity at Dublin. 
Needle. 
Date. 
Temp. 
No. of 
Qgcill’ns. 
Time of 
Ten 
Oscill’ns. 
Corrected 
Time of 
Ten 
Oscill’ns. 
Mean. 
Coeffie’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Hor. 
Intensity. 
Year. 
Month. 
D. 
H. 
M. 
Fah. 0 
Sees. 
Secs. 
Secs. 
Lond. 1. 
Cylinder. 
1836 
Nov. 
21 
4 
08 
451 
200 
36.13 
36.157 
44 
44 
44 
44 
44 
21 
44f 
44 
.14 
.168 
44 
44 
44 
44 
44 
39 
44| 
44 
.12 
.149 
36.158 
0.978 
0.935 
Bar. 
1836 
Nov. 
19 
4 
40 
40 
200 
39.77 
39.862 
44 
44 
44 
44 
44 
54 
39| 
150 
.74 
.833 
44 
44 
44 
21 
4 
53 
4M 
44 
.78 
.851 
39.849 
0.992 
0.938 
* This is easily done through the abstract contained in Major Sabine’s interesting report to the 
British Association, on the variation of the magnetic intensity observed at different points of the 
earth’s surface. From the Seventh Report of the British Association for the Advancement of Sci- 
ence, London, 1838. I have, however, referred to the originals, whenever they were accessible, 
in which cases they are quoted in my paper, without other acknowledgment. 80 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
These results can add nothing to the laboured deductions of the same ele- 
ment by Professor Lloyd and Major Sabine, but they are important here, as 
indicating the accuracy with wdiich the corrections for my needles are known, 
an interval of nine months having elapsed between the observations at Dublin 
and London. The mean of the three series with the two needles gives 0.936 
for the horizontal intensity at Dublin to that at London as unity, while the 
mean of the determinations of the experimenters just referred to is 0.940, the 
two extremes being 0.946 and 0.934.* 
EDINBURGH. 
The following observations were made at Canaan Park, near Edinburgh. 
The instrument was much out of order, and required much time and pains to 
obtain the results, which, after all, are not as accordant as usual: their number 
probably makes up for the want of close agreement. The numbers in the 
column of corrected results are reduced for the rate of the chronometer,! as 
well as for temperature. 
Observations for Horizontal Intensity at Edinburgh. 
Needle. 
Date. 
Temp. 
Number 
of 
Oscill’ns. 
Time of 
Ten 
Oscill’ns. 
Corrected 
Time of 
Ten 
Oscill’ns. 
Mean. 
Coeffic’t 
of 
Correction 
for 
Loss of 
Magnet’m. 
Hor. 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. ° 
Secs. 
Secs. 
Secs. 
Lond.1. 
Cylinder. 
1837 
Feb. 
4 
2i 
46 
250 
37.05 
44 
44 
44 
44 
21 
44 
270 
.11 
4 4 
44 
44 
44 
3 
45 
250 
.11 
44 
44 
44 
44 
31 
44 
44 
.08 
37.107 
37.107 
0.986 
0.895 
Bar. 
1837 
Feb. 
2 
4 
34 
248 
40.70 
44 
44 
44 
44 
4| 
33 
250 
.68 
44 
44 
44 
4 
5 
44£ 
330 
.75 
40.810 
40 810 
0.995 
0.897 
I do not find in either of Major Sabine’s reports, already referred to, a com- 
parison of the horizontal forces of magnetism at Edinburgh and London. Pro- 
* See Report on the Magnetic Isoclinal and Isodynamic Lines in the British Islands. By Major 
Edward Sabine. From the Eighth Report of the British Association for the Advancement of Sci- 
ence. London, 1839. For the early receipt of a copy of this report I am indebted to the author. 
t While at Edinburgh, the main spring of the chronometer gave way, and was replaced by Mr. 
Bryson. The watch had, subsequently, a very considerable losing rate, but I preferred to submit 
to this inconvenience to having frequent alterations made in it. 81 
AT TWENTY-ONE STATIONS IN EUROPE. 
fessor Forbes has compared Edinburgh and Paris, and gives the intensity at 
the former place to that at the latter as 0.8402 to unity. My direct determina- 
tion gives almost identically the same results; namely, 0.8405. Again, com- 
paring Edinburgh and Paris through London, I find 0.841 for the horizontal 
intensity at the former city. Farther, using my results at Edinburgh in a 
comparison of Dublin and London through Edinburgh, I find 0.936 for the 
relative horizontal intensities at Dublin and London, agreeing within 0.004 of 
the mean result of Professor Lloyd and Major Sabine’s observations. All 
these verifications go to show that my number for the relation of the horizon- 
tal intensities at Edinburgh and London is very nearly correct. 
The dip was determined, at the same time and place with those of the fore- 
going observations, by Professor Forbes, with a small three inch circle, to be 
71° 47'.5. This result differs but slightly from those of Major Sabine in 
September, 1836, and of Mr. Fox, in August, 1837, when reduced to this 
epoch, and I have employed it in determining the total intensity. Calculating 
this element from the mean of the horizontal intensities of the foregoing table, 
and using the dip observed by me at London, I find 1.013 for the total intensity 
at Edinburgh, that of London being unity. Major Sabine obtained, by the 
statical method, 1.023. I am at a loss to explain the difference between us. 
It does not, probably, depend upon an error in the dip used in my calculation, 
since, taking a mean of those which Major Sabine and Mr. Fox obtained at 
Edinburgh, and Major Sabine, Captain Ross, Professor Phillips, Mr. Fox, 
and Professor Lloyd, at London, reduced to this same epoch, and using these 
means with my horizontal intensity, the total intensity appears to be 1.014. If 
my result is erroneous, the error must be in the determination of the horizon- 
tal intensity, the numerous verifications of which render it improbable that this 
is wrong to any considerable extent. 
LONDON AND PARIS. 
As these stations are of importance as references in connecting the magnetic 
intensity in the United States with that in Europe, I bestowed great care upon 
the observations, and multiplied them. They were, besides, points to which I 
VII. V 82 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
intended to return a second time, and which, therefore, afforded the means of 
ascertaining the loss of magnetism of the needles. The number of needles em- 
ployed, and of observations made, may, perhaps, farther entitle these results to be 
allowed some weight in the determination of the relative intensity of magnetism 
at these two important European stations. The instrument for measuring the 
horizontal intensity was put in excellent order by Robinson, who also furnished 
the dipping circle and needles. Besides the horizontal needles which I ordi- 
narily used, I employed two others, and also observed by the statical method 
of Professor Lloyd. The observations were made in the summer of 1837, and 
again in 1838, the intervals between the respective series at London and Paris 
being quite short. The place of observation at London was near Captain Ross’ 
former residence, at Westbourne Green, and at Paris, in the garden of the 
observatory in the Magnetic Cabinet of M. Arago. The chronometer was 
compared, before and after the observations, with, the clock of the observatory 
at Paris, and with the standard of Messrs. Arnold and Dent, at London. 
Observations for Horizontal Intensity at London and Paris 
Place. 
Needle. 
Date. 
Temp. 
No. of 
Oscill’ns. 
Time of 
Ten 
Oscill’ns. 
Corrected 
Time of 
Ten 
Oscill’ns. 
Mean. 
Coeffic’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
M. 
Fah. ° 
Secs. 
Secs. 
Secs. 
Paris 1. 
Lond. 1 
London 
Cylinder 
1837 
June 
24 
12 
06, P. M. 
71 
242 
35.31 
35.369 
44 
44 
44 
44 
4 4 
30, 
76| 
280 
.29 
.349 
35.359 
1.069 
1.000 
Bar 
4 4 
44 
44 
2 
49, 
73j 
300 
38.704 
38.742 
4 4 
44 
44 
44 
3 
10, 
44 
44 
44 
44 
38.742 
1.066 
1.000 
H. R. 
4 4 
,« 
1 
36, 
77 
350 
31.23 
31.275 
44 
4 4 
44 
44 
2 
01, 
44 
44 
.29 
.335 
31.305 
1.066 
1.000 
H. B’t 
44 
44 
16 
3 
427 
72 i 
350 
25.01 
25.029 
(4 
44 
44 
4 4 
4 
01, 
72 
400 
.01 
44 
25.029 
1.062 
1.000 
Paris 
Cylinder 
4 4 
Aug. 
4 
10 
58, A. M. 
69 
300 
34.12 
44 
44 
44 
44 
44 
11 
23, 
44 
44 
.13 
44 
34.286 
.9958 
1.000 
0.936 
Bar 
44 
44 
44 
12 
42, P. M. 
70| 
300 
37.42 
4 4 
44 
44 
44 
44 
1 
02, 
70 
44 
.40 
44 
37.560 
.9980 
1.000 
0.938 
H. R. 
44 
July 
13 
12 
04, 
70| 
350 
30.18 
30.305 
44 
44 
44 
44 
44 
34, 
44 
44 
. .16 
.325 
30.315 
1.000 
0.938 
H. B’t. 
44 
44 
44 
10 
53, A. M. 
70 
400 
24.19 
24.286 
44 
44 
44 
44 
11 
10, 
69* 
44 
44 
44 
24.286 
1.000 
0.942 83 
AT TWENTY-ONE STATIONS IN EUROPE. 
Observations for Horizontal Intensity at London and Paris, continued. 
Place. 
Needle. 
Date. 
Temp. 
No. of 
Oscill’ns. 
Time of 
Ten 
Oscill’ns. 
Corrected 
Time of 
Ten 
Oscill’ns. 
Mean. 
Coeffic’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
M. 
Fah. ° 
Secs. 
Secs. 
Secs. 
Paris 1. 
Lond. 1. 
Paris 
Cylinder. 
1838 
July 
4 
1 
07, P. M. 
73k 
350 
34.956 
35.076 
66 
66 
66 
46 
1 
36, 
66 
326 
.944 
.066 
U 
66 
66 
17 
12 
04, 
72 
350 
.903 
.026 
66 
66 
64 
66 
66 
35, 
73 
66 
.850 
34.971 
u 
66 
66 
66 
1 
03, 
74 
66 
.934 
35.053 
66 
66 
66 
66 
2 
06, 
82k 
66 
.934 
.038 
ct 
66 
66 
64 
66 
29, 
83k 
66 
.931 
.035 
35.038 
1.000 
0.938 
Bar. 
66 
66 
4 
3 
34, 
73k 
350 
37.714 
37.812 
66 
66 
46 
46 
• 6 
56, 
72k 
66 
.703 
.805 
66 
66 
66 
17 
66 
16, 
84| 
300 
.763 
.811 
66 
66 
66 
66 
66 
36, 
85| 
66 
.792 
.836 
37.816 
1.000 
0.936 
London 
Cylinder. 
66 
Aug. 
15 
1 
03, 
65 
350 
36.232 
36.271 
<( 
66 
66 
66 
66 
25, 
66 
66 
.239 
.278 
36.274 
.9962 
1.066 
1.000 
Bar. 
66 
46 
66 
2 
23, 
66 
350 
39.032 
39.064 
66 
66 
66 
66 
66 
49, 
66 
66 
.030 
.062 
39.063 
.9982 
1.068 
1.000 
The final mean of these results gives the horizontal intensity at Paris 1.066, 
that at London being 1.000. By a series of observations with six needles, in 
1827, Major Sabine found the same element to be 1.071: the highest result 
which any one of his needles gave was 1.073, and the lowest 1.0675. 
The following observations of the dip were made at the same places with the 
foregoing. At Paris, in 1837, the observations with needle No. 2 were made 
at such a late hour as to be unsatisfactory, from a deficiency of light; I have, 
therefore substituted for them the dip given by the two needles used in the 
statical method, and corrected by a comparison of their results at London with 
those of the other two needles, the poles of which were reversed. Needle No, 
2 was in the hands of Mr. Robinson, for alteration, in 1838, and I have again 
used the corrected results given by the statical needles. The total intensities 
are calculated from the mean horizontal intensity and the observed dips. 84 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
Dip and Total Intensity at London and Paris 
Place. 
Date. 
Needle. 
Dip. 
Mean Dip. 
Total Intensity. 
Year. 
Month. 
D. 
Degs. 
Min. 
Degs. 
Mins. 
Lond. 1. 
Paris 1. 
London 
1837 
June 
16 
No. 1 
69 
18.3 
2 
17.4 
69 
17.8 
1.000 
1.020 
Paris 
It 
Aug. 
17 
Lloyd No. 1 
67 
16.9 
2 
21.3 
Mean, 
67 
19.6 
No. 1 
23.2 
67 
21.4 
0.980 
1.000 
Paris 
1838 
July 
10 
No. 1 
67 
16.4 
2 
16.6 
67 
16.5 
0.980 
1.000 
London 
(( 
Aug. 
15 
Lloyd No. 1 
69 
12.9 
No. 2 
12.3 
Mean, 
69 
12.6 
No. 1 
12.1 
69 
12.3 
1.000 
1.020 
The report of Major Sabine on the magnetic survey of the British Islands 
affords ample authentic materials for putting these results to the test. Pro- 
fessor Phillips, who observed the dip, in May, 1837, at the same place where 
my observations were made, found it 69° 20'.2; and again, in March, 1838, 
69° 18'.2, which, reduced to the epoch of my observations, at the rate of a dimi- 
nution of O'.2 per month, would give (the correction being additive) 69° 20'.4. 
The dip observed by Major Sabine in Regent’s Park, in July, 1837, reduced 
to the same epoch, is 69° 18'.9, and by an observation in November, 1837, 
69° 25'.0. That found by Capt. James Ross, at Westbourne Green, in Au- 
gust, 1837, similarly reduced, gives 69° 20'.8; in June and July, 1838, 69° 17'.0; 
and in December, 1838, 69° 17’.4. That of Professor Lloyd, in 1836, also, 
reduced, is 69° 20'.8; and of Mr. Fox, in May and June, 1838, 69° 20'.5. The 
mean of all these determinations, omitting the dip of 69° 25'.0, is 69° 19’.5. I 
am not acquainted with any series of determinations, at the same place, by dif- 
ferent observers, and with different instruments, which agree so closely, and 
consider it, therefore, as an important point in verifying my results, that the 
dip observed in 1837 agrees within 1'.7 of the mean of those just referred to. 
The second determination of 69° 12'.3, in 1838, is in defect 4'.8, supposing the 
annual decrease of dip to be 2'.4, a difference which is admissible, since nearly AT TWENTY-ONE STATIONS IN EUROPE. 
85 
as great a one is to be found among the foregoing results. The determinations 
of the dip at Paris agree very well with that given by Professor Forbes, on 
the authority of M. Arago, in July, 1835,* namely, 67° 24'.0. An annual 
diminution of dip of 2'.8 would give, in August, 1837, 67° 18'.2, while I found 
67° 21'.4; and in July, 1838, 67° 15'.6, while my result was 67° 16'.5. 
It is obvious, then, that my value of the total intensity is correct or not, ac- 
cording as the horizontal intensity has or has not been, accurately determined. 
I shall return to this, after stating the results obtained by the statical method 
of Professor Lloyd. As the observations in 1837, by this method, were made 
at the short interval of a month from each other, I have not thought it neces- 
sary to apply a correction to them, the whole loss of magnetism, during the 
year, by either needle, having amounted to less than 0.01. 
Observations for Total Intensity at London and Paris, by the Statical Method. 
Place. 
Date. 
Needle. 
Temp. 
Dip when 
loaded, 
or 
Angle 0. 
Dip reduced 
to August, 
or 
Angle (f. 
Total 
Intensity, 
or 
Cor. 0 
Month. 
Year. 
Fah. ° 
Sui (iT — 0) 
London 
June 
1837. 
No. 1, 
74k 
21° 
59'.0 
69° 
17'.5 
Paris 
Aug. 
ti 
it 
72| 
24 
47 .3 
67 
21 .0 
0.979 
London 
June 
a 
No. 2, 
74k 
19 
13 .5 
Paris 
Aug. 
it 
it 
72 i 
22 
48 .2 
0.976 
London 
Aug. 
1838. 
No. J, 
65 
22 
31 .3 
69 
12 .3 
Paris 
July 
it 
it 
75 
25 
41 .7 
67 
16 .2 
0.9791 
London 
Aug. 
u 
No. 2, 
65 
19 
59 .4 
Paris 
July! 
it 
U 
77 
23 
12 .5 
0.980t 
The horizontal intensity deduced from these results by using the dip already 
given, is 1.065, agreeing closely with the determination by the method of 
vibrations. This latter determination rests upon 4072 oscillations at one 
station, and 6426 at the other, besides the verification by the statical method. 
The foregoing results are collected in the following table. 
* See the paper of Professor Forbes before referred to, in the Edinburgh Transactions, vol. xiv. 
p. 27. 
t A small correction has been applied for the effect of temperature, amounting to 0.003 and 
0.002 in the two cases respectively. 
VII.—w 86 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
Horizontal and Total Intensities and Dip at London and Paris. 
Date. 
Needle. 
Horizontal 
Intensity. 
Total Intensity. 
Magnetic Dip. 
Paris. 
London. 
Paris. 
London. 
Paris. 
London. 
1837. 
June, July, Aug. 
Cylinder. 
1.069 
1.000 
0.982 
1.000 
67° 21'.4* 
69° 17\8t 
Bar. 
1.066 
0.980 
H. R. 
1.066 
0.980 
H. B. 
1.062 
0.976 
Lloyd No. 1. 
1.067 
0.980 
“ “ 2, 
1.063 
0.976 
1838, 
July, Aug. 
Cylinder. 
1.066 
0.980 
67° 16.5 
69° 12'.3 
Bar. 
1.068 
0.981 
Lloyd No. 1. 
1.067 
0.981 
“ “ 2, 
1.066 
0.980 
Mean, 
1.066 
1.000 
0.979 
1.000 
1.000 
0.938 
1.000 
1.021 
BRUSSELS. 
The horizontal intensity at Brussels compared with that at Paris being well 
known through the observations of M. Quetelet and others, it is important to 
me as a verification of my results, and as connecting stations in the United 
States with those in Europe, to compare my determinations with those already 
on record. The dip at Brussels is also, no doubt, accurately known from the 
regular observations of M. Quetelet since 1827; and I regretted that an acci- 
dent which had happened to my dipping circle at Paris prevented me from 
farther putting its accuracy to the test. The observations for horizontal in- 
tensity were made in the garden of the Observatory. The chronometer was 
compared with the observatory clock before and after the observations. 
* The mean of this result and that obtained in 1838, reduced to August 16th, 1837, allowing a 
diminution of dip yearly of 2'.8, is 67° 20'.8. 
t The mean of this result and that in 1838, reduced to June 16th, allowing an annual decrease 
of dip of 2'.4, (see Major Sabine’s Report on the Magnetic Survey of the British Islands,) is 
69° 16'.0. AT TWENTY-ONE STATIONS IN EUROPE. 
87 
Observations for Horizontal Intensity at Brussels. 
Needle. 
Date. 
Temp. 
Number 
of 
Oscill’ns. 
Time of 
Ten 
Oscill’ns. 
Corrected 
Time of 
Ten 
Oscill’ns. 
Mean. 
Correction 
for 
Loss of 
Magnetism. 
Hor. 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. 0 
Secs. 
Secs. 
Secs. 
Paris 1. 
Cylinder. 
1838 
July 
25 
2|, 
P.M. 
62 
300 
35.596 
35.640 
44 
44 
44 
44 
2$, 
44 
61 
300 
.599 
.644 
35.642 
1.0026 
0.968 
Bar. 
U 
44 
44 
3|, 
4 £ 
60 
350 
38.366 
38.417 
44 
44 
44 
44 
5s, 
44 
57 
350 
.334 
.398 
38.407 
1.0002 
0.970 
The mean of these results, 0.969*, is in close accordance with the results 
before referred to as given by M. Quetelet, the mean of the several series of 
observations made at Brussels between 1828 and 1838 being nearly 0.964. 
BERLIN. 
I am indebted for an opportunity to make this set of observations to the 
kindness of Professor Encke, who put his convenient magnetic observatory 
at my disposal, and removed from it the variation magnetometer and dipping 
needle which it contained: without this, I could not have observed at this sea- 
son of the year. In my first attempts to obtain the dip I was unsuccessful, 
owing to the great loss of force which my magnets for reversing the poles of 
the dipping needle had sustained during a circuitous journey from Switzerland 
to this capital. The magnets were retrenched by CErtel, and the results then 
obtained appear worthy of confidence. Since this time I have taken the pre- 
caution to oscillate the dipping needles before observing with them after the 
reversion of the poles, to ascertain that they are charged nearly, or quite, to 
saturation. As the periods which elapsed between these observations and 
those which preceded and succeeded them, at Paris, were not very different, I 
have calculated the intensity at Berlin in reference to both the series at Paris, 
applying the correction for the loss of magnetism by the needles, deduced as 
* This number differs by 0.001 from the result given by M. Quetelet in the Bulletin of the Brus- 
sels Academy, vol. v. p. 481. In the numbers communicated to him I had applied a correction for 
the loss of magnetism of the needles which was too high by nearly this difference; which is, how- 
ever, entirely unimportant. 88 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
already stated. The coincidence of the two results shows strikingly the accu- 
racy with which the curve already described supplies the data for the correc- 
tion of the loss of force by the horizontal needles. 
The chronometer was compared with the observatory clock. 
Observations at Berlin. 
For Horizontal Intensity. 
Needle. 
Date. 
Temp. 
No. 
of 
Series. 
No. of 
Oseill’ns. 
Time of 
Ten 
Oscill’ns. 
Corrected 
Time of 
Ten 
Oscill’ns. 
Correction 
for 
Loss of 
Magnet’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. ° 
Secs. 
Secs. 
Paris 1. 
Cylinder 
1837 
Dec. 
16 
2, P.M. 
37| 
2 
690 
34.966 
35.006 
1837. 
1.015 
0.974 
1838. 
0.975 
0.977 
Bar 
1837 
U 
<< 
2\ “ 
35 
2 
660 
37.886 
37.993 
1837. 
1.005 
0.983 
1838. 
0.993 
0.984 
Mean, . . 
0.979 
For Dip. 
1837, Dec. 29, 
Needle No. 1 
No. 2 
, 68° 06'.5 
,68 10.6 
Mean, 68° 08'.5. 
Total Intensity compared with Paris 
as unity, 
1.0145. 
The horizontal intensities of Berlin and Paris were compared by M. Rud- 
berg, who made the relation 0.974, and by M. Quetelet,* who gave 0.975 for 
the relative intensities. My result differs but slightly from these. 
The dip at Berlin is very well known from a series of observations extend- 
ing from 1806 to 1837, and my result can add nothing to the knowledge of this 
element, but as obtained with the same instrument which was used at Paris, 
the total intensity will be, probably, a nearer approximation by using it than 
* Annuaire de l’Observatoire de Bruxelles pour l’an 1834, p. 266. On the next page M. Quete- 
let gives 0.9886 for the relative intensities, but this is doubtless a mistake. AT TWENTY-ONE STATIONS IN EUROPE. 
89 
by employing in the calculation the more accurate determination of the long 
series just referred to. 
Professor Encke has determined from this series a formula by which the 
dip may be calculated for any epoch, namely, S = 68° 7'.3 — 3'.52 (t — 1836,) 
in which S is the dip and t the year or fraction of a year. The dip in Decern* 
ber, 1837, calculated from this formula, is 68° 00'.4, from which my result dif- 
fers about eight minutes. 
MM. Humboldt and Gay Lussac determined, in 1809, the relative inten- 
sities at Berlin and Paris to be 1.014; M. Erman, in 1828, and M. Quetelet 
in 1829, 1.0165.* My determination is 1.0145. 
VIENNA. 
These observations were made in the Botanic Garden, upon the upper 
platform. The chronometer was compared, before and after the observations, 
with the observatory clock. The time of ten oscillations and the dip are com- 
pared with the mean of the observations at Paris in 1837 and 1838, in calcu- 
lating the horizontal and total intensities. 
Observations at Vienna. 
For Horizontal Intensity. 
Needle. 
Date. 
Temp. 
No. of 
Series. 
No. of 
Oscill’ns. 
Time of 
Ten 
Oscill’ns. 
Coeffie’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. ° 
Secs. 
Paris 1.000. 
Cylinder. 
Bar. 
1838 
U 
March 
(( 
23 
ii 
3|, P.M. 
4£, “ 
58.3 
57.8 
2 
2 
700 
700 
33.436 
36.043 
1.0076 
1.0023 
Mean, 
1.084 
1.096 
1.090 
For Dip. 
1838, March 21, Needle No. 1, 64° 45'.8. 
No. 2, 53.7. Mean, 64° 49'.7. 
Total Intensity compared with Paris as unity, 0.989. 
The only published observations of magnetic intensity at Vienna with which 
I am acquainted are those quoted by Major Sabine, in his recent report, as 
* Major Sabine’s Report on the Magnetic Intensity of the Earth. 
VII. X 90 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
made by Keilhau and Boeck, and which give the total intensity at Vienna, as 
compared with Paris, 0.983, differing from the above only 0.006. 
The numbers for the horizontal intensity furnished by the two needles some- 
times, as in this particular case, differ; and, in general, the greater relative in- 
tensity is given by the bar needle. After an examination of various causes 
which suggested themselves as likely to produce this result, I am still at a loss 
to explain it. It is not due to an ill-ascertained correction for the loss of mag- 
netic force, nor for temperature, nor to a want of horizontality in the magnetic 
axis of the needle. The mode of observing renders the limits of error in the 
separate sets of observations much below these differences. It was my prac- 
tice in observing to employ the cylinder needle which has a very small cor- 
rection for temperature first, and, mean while, to place the other in the shade, 
so as to avoid an error from its not having acquired the temperature of the sur- 
rounding air. 
TRIESTE AND VENICE. 
The observations at Trieste were made in the Botanical Garden, and those 
at Venice in the garden of the Armenian Convent, on the Island of St. La- 
zarus. 
Observations at Trieste and Venice. 
For Horizontal Intensity. 
Place. 
Needle. 
* Date. 
Temp. 
No. of 
Series. 
No. of 
Oscill’ns. 
Time of 
Ten 
Oseill’ns 
at 60°. 
Coeffic’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. ° 
Secs. 
Paris 1. 
Trieste 
Cylinder 
1838 
April 
4 
10|, A. M. 
54.0 
2 
700 
32.889 
1.0091 
1.121 
Bar 
4 4 
44 
44 
Ill, “ 
54.5 
2 
580 
35.426 
1.0024 
1.135 
Mean, 
1.128 
Venice 
Cylinder 
1838 
April 
11 
12|, P. M. 
67.5 
2 
700 
32.876 
1.0097 
1.122 
Bar 
44 
4 4 
44 
1 1 “ 
67.6 
2 
700 
35.393 
1.0029 
1.137 
Mean, 
1.129 
For Dip. 
Trieste, 1838, April 4th, Needle No. 1, 
03° 19'.1 
No. 2, 
“ 22.5 
Mean, 
63° 20'.5 
Venice, 1838, April lltli, Needle No. 1 
, 63° 18'.9 
No. 2 
, “ 24 .9 
Mean 
, 63° 21'.9 
Total Intensity at Trieste, compared with Paris as 
unity, 0.970, 
4 4 
44 
Venice, 
44 
44 
4 4 
“ 0.9715. AT TWENTY-ONE STATIONS IN EUROPE. 
91 
In this table the mean time of the oscillations at Paris and the mean of the 
observed dips in 1837 and 1838, is taken as the unit of reference in calculating 
the relative horizontal and total intensities. 
The total intensity at Trieste, compared with Paris, is given by Major Sa- 
bine, in his report before referred to, as determined by Messrs. Keiliiau and 
Boeck, in 1826, as 0.977; differing from the mean of my results 0.007, the 
difference between us having a contrary sign from that at Vienna. M. Que- 
telet * gives the horizontal intensity at Venice as 1.1566, which is much 
greater than my number. 
ROME AND NAPLES. 
The observations at Rome were made at two different stations; one out of 
the region of the volcanic tufa upon which the city is built, upon the calcare- 
ous formation of Monte Mario, in the garden of the Villa Mellini, the other 
in the temple of Venus and Rome, opposite to the Colosseum. At the latter 
station a curious instance of local attraction occurred: I had selected a block 
of marble, apparently free from iron fastenings of any sort, as the resting place 
for the instrument, and finding results very discordant from those obtained on 
the Monte Mario, I next placed the instrument in a brick niche, to examine if 
the local attraction were common to the whole station. The results obtained 
when the instrument was in the niche were so different from the former that I 
placed it again upon the block, to ascertain if any mistake had occurred, but 
found again the same anomaly as at first. There was, probably, some iron be- 
neath the pavement upon which the block of marble rested, suggesting the ne- 
cessity for caution in the selection of these places of observation. 
Fearing the influence of the ferruginous nature of the volcanic tufa upon 
which Naples is built,f I went to A versa, about eight miles to the north of the 
city. The place of observation was in the large garden attached to the Asy- 
lum for the Insane. 
* Annuaire de 1’Observatoire de Bruxelles pour l’an 1834. 
11 certainly did not at that time remember that M. Quetelet had expressed his opinion that 
there was no local disturbance from this cause, or I should have deferred to his authority. Never- 
theless, the precaution, though attended with some inconvenience, was not amiss. 92 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
At Rome the chronometer was compared, before and after the observations, 
with the observatory clock of the Roman College, and, at Naples, with that of 
the Royal Observatory. 
The horizontal intensity observed at Paris, for 1838, is taken as unity in the 
calculations, the correction for loss of force in the needles being applied for the 
same epoch. The dip which is used in calculating the total intensity is a mean 
of that actually observed at Paris in 1838, and of that which would result from 
applying the yearly diminution of 2'.8 to the dip observed in 1837. 
Observations at Rome and Naples. 
For Horizontal Intensity. 
Place. 
Needle. 
Date. 
Temp. 
No. 
of 
Series. 
No. of 
Oscill’ns. 
Time of 
Ten 
Oscill’ns. 
at 60°. 
Coeffic’t 
of 
Correction 
for 
Loss of 
Magnet’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. ° 
Secs. 
Paris 1. 
Rome* 
Cylinder 
1838 
May 
18 
8£, A. M. 
67.3 
2 
650 
31.574 
0.9935 
1.223 
Bar 
a 
66 
66 
91, “ 
67.0 
2 
600 
34.122 
0.9981 
1.226 
Romef 
Cylinder§ 
tt 
66 
66 
P. M. 
65.0 
1 
350 
31.539 
0.9935 
1.226 
u 
66 
66 
66 
66.2 
1 
350 
31.777 
Rejected. 
Mean, 
1.225 
Naples X 
Cylinder 
1838 
May 
7 
8, A. M. 
76.2 
2 
700 
31.290 
0.9921 
1.244 
Bar 
66 
(( 
66 
Ill “ 
75.2 
1 
350 
33.674 
0.9977 
1.258 
Mean, 
1.249 
For Dip. 
Rome,|| 1838, May 15, Needle No. 1, 60° 
13'.1 
18, “ 
No. 2, “ 
14 .9 
Mean, 60° 14'.0. 
1838, 
M ay 7 
, Needle No. 1, 59° 
04'.8 
66 
66 
No. 2, “ 
05 .5 
Mean, 59° 05'. 1. 
Total Intensity at Rome, compared with Paris as unity, 0.9525. 
66 
66 
Naples, 
66 
it 
66 
“ 0.9380. 
In taking the means for the horizontal intensity, weight is allowed in pro- 
portion to the number of oscillations observed. 
The observations at Rome confirm the statement of M. Quetelet, that no 
effect is produced upon the needle by the volcanic tufa. 
* Monte Mario. t Temple of Venus and Rome. t Aversa. 
§ In niche, on stone. || Monte Mario. If Aversa. 93 
AT TWENTY-ONE STATIONS IN EUROPE. 
The numbers assigned for the horizontal intensities at Rome and Naples, by 
M. Quetelet, are, respectively, 1.2471 and 1.2869, differing very considerably 
from my results. My total intensities agree, however, very nearly with those 
found by Humboldt and Gay Lussac, which were, for Rome, 0.945, and for 
Naples, 0.938. 
FLORENCE AND MILAN. 
The observations at Florence were made in the Boboli Gardens; those at 
Milan in the garden of M. Kramer, near the Porta Nuova. The chronome- 
ter was compared, at both places, with the observatory clock. 
The same data at Paris, which were referred to under the the head of Rome 
and Naples, were used in the calculations in the following table. 
Observations at Florence and Milan. 
For Horizontal Intensity. 
Place. 
Needle. 
Date. 
Temp. 
No. of Series. 
No. of 
Oscillations. 
Time of 
Ten 
Oscill’ns 
at 60°. 
Coeffic’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. 0 
Secs. 
Paris 1. 
Florence 
Cylinder 
1838 
May 
28 
2f,P.M. 
68.2 
2 
700 
32.395 
.9947 
1.164 
Bar 
6 4 
66 
66 
3|, “ 
67.0 
2 
66 
34.838 
.9985 
1.176 
Mean, 
1.170 
Milan 
Cylinder 
1838 
June 
10 
1, P. M. 
73.7 
2 
600 
33.269 
.9964 
1.106 
Bar 
66 
66 
66 
2, “ 
72.1 
2 
6 6 
35.765 
.9989 
1.117 
Mean, 
1.112 
For Dip. 
Florence, 1838, May 28th 
, Needle No. 
L, 62° 
06'.5 
No. 2, “ 
04 .5 
Mean, 
62° 05'.5 
Milan, 1838, June 10th, 
Needle No. 1 
63° 54'. 1 
No. 2 
“ 55 .4 
Mean, 63° 54'.7 
Total Intensity at Florence, compared with Paris as unity, 0.965. 
46 
66 
Milan, 
66 
66 
66 
“ 0.972. 
The same numbers for Paris being employed as in the preceding calcula- 
tions, and referring to 1838,1 thought it might be satisfactory to ascertain if any 
part of the differences of horizontal intensity, as shown by the two needles, 
(amounting, in the results at Florence and Milan, to .012 and .011,) could be 
explained by an erroneous correction for loss of magnetism. Referring the 
horizontal intensities to 1837, however, when the correction has the contrary 
effect from that in the table, the same difference results. 
VII. Y 94 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
Nor does this depend upon some peculiarity in the observations at Paris, 
since, referring to the observations at London, and taking the horizontal in- 
tensity there as unity, nearly the same difference appears. 
The horizontal intensities determined by M. Quetelet at these two stations 
both exceed my results, his number for Florence being 1.1830, and for Milan 
1.1335. The total intensities obtained by MM. Humboldt and Gay Lussac 
were, for Florence, 0.9481, and for Milan 0.9733, both of which numbers are 
less than mine.* 
TURIN AND CHAMBERI. 
The place of observation at Turin was in the Botanic Garden; at Cham- 
beri, in the park of the Count de Boignes, a short distance only from the 
town. At Turin the chronometer was compared with the observatory clock, 
and the same rate was applied at Chamberi. The comparison is made with 
the observations at Paris in 1838. 
Observations at Turin and Chamberi. 
For Horizontal Intensity. 
Place. 
Needle. 
Date. 
Temp. 
to 
5 
m 
o 
6 
£ 
G 
C+H O 
O 
• d 
o -n 
xrx 
o 
Time of 
Ten 
Oscill’ns. 
at 60°. 
Cceffic’t 
of 
Corr’n 
for 
Loss of 
Magn’m, 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. u 
Secs. 
Paris 1. 
Turin 
Cylinder 
‘ Bar 
1838 
66 
June 
66 
17 
( ( 
11, A. M. 
12, M. 
82.5 
83.0 
2 
2 
600 
It 
33.440 
36.149 
.9987 
.9992 
Mean, 
1.096 
1.093 
1.0945 
Chamberi 
Cylinder 
Bar 
1838 
66 
June 
66 
21 
66 
12f P. lM. 
2 
78.2 
77.5 
2 
2 
700 
It 
33.539 
36.235 
.9989 
.9993 
Mean, 
1.090 
1.088 
1.089 
For Dip. 
Turin, 1838, June 17, Needle No. 1, 63° 48'.8 
18, “ No. 2, “ 55 .6 Mean, 63° 52'.2. 
Chamberi, 1838, June 21, Needle No. 1, 64° 31'.5 
No. 2, “ 37 .5 Mean, 64° 35'.0. 
Total Intensity at Turin, compared with Paris as unity, 0.959. 
“ “ Chamberi, “ “ “ “ 0.979. 
* The authorities for these numbers are the same as previously quoted. In the remainder ol the 
paper, unless the contrary is stated, the numbers are derived from the same sources, namely, the 
Annual of the Brussels Observatory for 1834, or the Transactions of the Brussels Academy of Sci- 
ences, vol. vi., and the Report of Major Sabine on the Magnetic Intensity. AT TWENTY-ONE STATIONS IN EUROPE. 
95 
M. Quetelet assigns 1.112 as the horizontal intensity at Turin, and MM. 
Humboldt and Gay Lussac give 0.9911 as the total intensity. The latter 
number exceeds my determination very considerably. 
LYONS. 
These observations were made in a meadow to the south-east of Lyons, and 
across the Rhone from the city. In reducing the time of ten oscillations for 
the rate of the chronometer, the mean of the rates at Turin and Paris, which 
differed very slightly, has been employed. 
Observations at Lyons. 
For Horizontal Intensity. 
Place. 
Needle. 
Date. 
Temp. 
No. of Series. 
No. of 
Oscillations. 
Time of 
Ten 
Oscill’ns 
at 60°. 
Coeffie’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. 0 
Secs. 
Paris 1. 
Lyons 
Cylinder 
Bar 
1838 
44 
June 
44 
25 
44 
12J, P. M. 
2i, “ 
75.7 
74.1 
2 
2 
700 
750 
33.739 
36.391 
.9991 
.9995 
Mean, 
1.077 
1.079 
1.078 
For Dip. 
Lyons, 1838, June 24, Needle No. 1, 64° 49'.5. 
No. 2, 48.6. Mean, 64° 49'.0. 
Total Intensity at Lyons, compared with Paris as unity, 0.978. 
According to MM. Humboldt and Gay Lussac, the total intensity at Ly- 
ons is .9889. 
CHAMOUNI AND THE FLEGIERE. 
i 
The place of observation which appeared to me most suitable, at the time of 
my visit to Chamouni, was in a field in rear of, and at some distance from, the 
Union Hotel. On the Flegiere the observations were made not far from, and 
about thirty feet above, the point where the cross is placed. The height of 
this point above the Valley of Chamouni is, in round numbers, about 3500 feet, 
and the valley itself is 3400 feet above the level of the sea. 96 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
These observations having been made in August, 1837, are compared with 
those at Paris in 1837, the dip being obtained, however, as in the similar case 
of 1838, by using both series of observations. The rate of the chronometer de- 
termined at Geneva was used in the reduction. 
Observations at Chamouni and the Flegiere, 
For Horizontal Intensity. 
Place. 
Needle. 
Date. 
Temp. 
No. of Series. 
No. of 
Oscillations. 
Time of 
Ten 
Oscill’ns 
at 60°. 
Coeffic’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fall. ° 
Secs. 
Paris 1. 
Chamouai 
Cylinder 
1837 
Aug. 
26 
9£,P.M. 
53.0 
1 
150 
32.902 
1.002 
1.088 
Bar 
44 
44 
10, “ 
50.0 
2 
300 
36.006 
1.001 
1.089 
Mean, 
1.0885 
The Flegiere 
Cylinder 
1837 
Aug. 
26 
12, M. 
68.0 
2 
650 
32.768 
1.002 
1.097 
Bar 
44 
44 
44 
12|, P. M. 
69.5 
1 
300 
35.945 
1.001 
1.101 
Mean, 
1.099 
For Dip. 
Chamouni, 1837, Aug. 26, Needle No. 1 
, 64° 38'.7 
No. 2, 64 37 .7 
Mean, 64° 38'.2. 
The Flegiere, 1837 
, Aug. 26, 
Needle No. 1, 64° 35'.8. 
Total Intensity at Chamouni, compared with Paris as unity, 0.979 
44 
44 
on the Flegiere, “ 
4 4 
44 
“ 0.987 
The horizontal intensity in the Valley of Chamouni, according to Professor 
Forbes, is 1.076,* and to M. Quetelet, 1.0935.f My result agrees nearly 
with the latter. The higher station presents a greater horizontal and total in- 
tensity than the lower, contrary to the general deduction from the laboured and 
ingenious memoir of Professor Forbes on this subject. It is worthy of remark, 
however, that the number given by Professor Forbes for the horizontal inten- 
sity at the Jardin is greater than that for the valley. M. Quetelet, on the 
contrary, found a less horizontal intensity on the Mer de Glace than at Cha- 
mouni. The anomaly is probably real, and adds another to the instances pre- 
sented by Professor Forbes, of the difficulties of the problem of which he has 
* Edinburgh Transactions, vol. xiv., part I. 
t Annuaire de l’Observatoire de Bruxelles pour l’an 1834. AT TWENTY-ONE STATIONS IN EUROPE. 
97 
successfully undertaken the solution. The dip given by Professor Forbes, at 
Chamouni, is 65° 00', and at the Jardin, 64° 58', both differing considerably 
from my results. 
GENEVA. 
These observations were made in the garden of M. Prevost-Martin, not 
far from the city; those with the cylindrical needle on the 24th of August and 
1st of September, those with the bar on the first occasion; the dip was mea- 
sured on the second. The observations at Chamouni intervened between the 
two sets at Geneva. The loss of the chronometer was ascertained from the 
standard near the Church of St. Peter, which is rated for the use of the watch- 
makers. 
The numbers for Paris used in the reductions were obtained as stated under 
the head of Chamouni. 
Observations at Geneva. 
For Horizontal Intensity. 
Place. 
Needle. 
Date. 
Temp. 
No. of Series. 
No. of 
Oscillations. 
Time of 
Ten 
Oscill’ns 
at 60°. 
Coeffie’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. 0 
Secs. 
Paris 1. 
Geneva 
Cylinder 
1837 
Aug. 
24 
1, P.M. 
81.2 
2 
662 
32.904 
1.0023 
1.088 
<( 
6t 
Sept. 
1 
n, “ 
68.5 
1 
300 
33.033 
1.0032 
1.081 
Bar 
ti 
Aug. 
24 
it, “ 
82.0 
2 
650 
36.048 
1.0008 
1.086 
Mean, 
1.086 
For Dip. 
Geneva, 
1837, 
Sept. 1, Needle No. 1, 64° 
52'. 4. 
No. 2, 
47 .3. 
Mean, 64° 49'.8. 
Total Intensity at Geneva, compared with Paris as 
unity, 0.984. 
The horizontal intensity at Geneva, compared with that at Paris, is stated 
by M. Quetelet* to be 1.0805, and by Professor FoRBEsf, 1.071; my own re- 
sult agrees best with the former. Professor Forbes determined the dip, in 
August, 1832, to be 65° 05', and states that it was found, in 1825, by M. Arago, 
* Annuaire de l’Observatoire de Bruxelles, &c., 1834. 
t Edinburgh Transactions, vol. xiv. 
VII.—z 98 
OBSERVATIONS OF THE MAGNETIC INTENSITY 
to be 65° 48'.5. Adopting 2'.8 as the annual decrease of the dip at Geneva, the 
observations of Professor Forbes would give, for the epoch 1837, 64° 51'.0, and 
those of M. Arago, 65° 14'.9. 
BRIENTZ AND THE FAULHORN. 
These observations were made at places only about fourteen miles apart, hut 
differing in elevation 6800 feet: the lower station itself (Brientz) is about 8900 
feet above the level of the sea. The Faulhorn was one of the stations of Pro- 
fessor Forbes in his Alpine observations; and Brientz is about twelve miles 
W. N. W. of another of his stations, Meyringen. 
The observations at Brientz were made in a field in rear of, and about a hun- 
dred yards from the White Cross Hotel; those at the Faulhorn nearly on the 
very summit, and as far from the chalet as the ground would permit. 
The chronometer was rated at Zurich, and the rate, which differed but 
little from that found at Geneva, has been applied in the following table. The 
numbers already referred to for Paris, in 1837, have been used in the calcu- 
lations. 
Observations at Brientz and the Faulhorn. 
For Horizontal Intensity. 
Place. 
Needle. 
Date. 
Temp. 
No. of Series. 
No. of 
Oscillations. 
Time of 
Ten 
Oscill’ns. 
at 60°. 
Coeffic’t 
of 
Corr’n 
for 
Loss of 
Magn’m. 
Horizontal 
Intensity. 
Year. 
Month. 
D. 
H. 
Fah. ° 
Secs. 
Paris 1. 
Brientz 
Cylinder 
1837 
Sept. 
22 
11, A.M. 
65.0 
2 
700 
33.162 
1.0056 
1.075 
Bar 
<( 
Ct 
U 
12|, P.M. 
64.8 
2 
600 
36.141 
1.0020 
1.082 
Mean, 
1.078 
The Faulhorn 
Cylinder 
1837 
Sept. 
20 
3 P. M. 
50.5 
2 
700 
33.078 
1.0054 
1.080 
Bar 
U 
U 
4 “ 
43.7 
2 
600 
36.082 
1.0017 
1.085 
Mean, 
1.082 
For Dip. 
Brientz, 1837, Sept. 22, Needle No. 
1, 64° 59'.5 
No. 2, 65 15 .0 
Mean, 65° 06'.7. 
The Faulhorn, 1837, Sept. 20, Needle No. 1 
65° 0T.5 
No. 2 
, “ 01 .9 
Mean, 65° 01'.7. 
Total Intensity at Brientz, compared with Paris as unity, 0.9869. 
U 
ii 
Summit of the Faulhorn 
ii 
“ 0.9874. 
- AT TWENTY-ONE STATIONS IN EUROPE. 
99 
The difference in the dip at Brientz, as shown by the two needles, (No. 1 
and No. 2,) is very considerable, and, from the separate observed quantities, 
the results by No. 2 would appear more worthy of confidence than that by 
No. 1. 
The two horizontal needles, oscillated by Professor Forbes, on the Faulhorn, 
gave 1.071 and 1.060, mean 1.065 for the horizontal intensity compared with 
Paris, and the needle oscillated at the lower station, Meyringen, for compari- 
son, 1.075. My results, both at the upper and lower stations, exceed these, be- 
ing 1.082 and 1.078. The difference of the horizontal intensities at the upper 
and lower stations appears equally from my series and that of Professor Forbes 
to have been very small; less, in fact, than the differences between two needles 
at the same station. 
I am not aware that Professor Forbes determined the dip at his two corre- 
sponding stations. Using the mean dip for Brientz, the total intensity at the 
lower station appears very nearly the same with that at the upper; using the 
dip given by needle No. 1, it would, of course, be less; and using that shown 
by needle No. 2, it would exceed the total intensity at the upper station by 
only .0046. 
The details given in the preceding pages appear to me essential, in order to 
a just conclusion as to the character of the results, and for reference in regard 
to the localities and circumstances of the observations. The comparisons of 
my conclusions with those of others, as far as I am acquainted with them, will 
probably be found convenient, and, in some cases, had a specific object in 
reference to these observations themselves. The results being thus unavoid- 
ably scattered, I have thought it best, in conclusion, to present them in a sin- 
gle table, divested of particulars. 100 
OBSERVATIONS OF THE MAGNETIC INTENSITY, &C. 
The results are arranged in the order of the total intensities and columns are 
inserted for the latitude and longitude of the places. 
No. 
Place. 
Latitude. 
Longitude 
from 
Paris. 
Date. 
Horizontal 
Intensity. 
Dip. 
Total 
Intensity. 
o 
/ 
■d 
/ 
Paris = 1. 
o ! 
1 
/ 
Paris = 1. 
1 
Edinburgh. 
55 
57 N. 
5 
32W. 
Feb. 3, 1837. 
0.841 
# 
2 
Dublin. 
53 
23 “ 
8 
41 “ 
Nov. 20, 1836. 
0.879 
* 
3 
London. 
51 
31 “ 
2 
26 “ 
June 16, 1837. 
0.939f 
69 
16.0 
1.021 
4 
Brussels. 
50 
51 “ 
2 
02 E 
July 25, 1838. 
0.969 
5 
Berlin. 
52 
32 “ 
11 
02 “ 
Dec. 16, 1837. 
0.979 
68 
08.5 
1.014 
6 
Paris. 
48 
50 “ 
0 
00 “ 
Aug. 17, 1837. 
1.000 
67 
20.8 
1.000 
7 
Vienna. 
48 
13 “ 
14 
02 E. 
March 23, 1838. 
1.090 
64 
49.7 
0.989 
8 
The Flegiere. 
Aug. 26, 1837. 
1.099 
64 
35.8 
0.987 
9 
Brientz. 
Sept. 22, “ 
1.078 
65 
06.7 
0.987 
10 
The Faulhorn. 
Sept. 20, “ 
1.082 
65 
01.7 
0.987 
11 
Geneva. 
46 
12 “ 
3 
49 “ 
Aug. 25, “ 
1 1.086 
64 
49.8 
0.984 
12 
Chamberi. 
June 21,1838. 
1.089 
64 
35.0 
0.979 
13 
Chamouni. 
Aug. 26, 1837. 
1.088 
64 
38.2 
0.979 
14 
Lyons. 
45 
46 “ 
2 
29 “ 
June 25, 1838. 
1.078 
64 
49.0 
0.978 
15 
Milan. 
45 
28 “ 
6 
51 “ 
June 10, “ 
l.lll 
63 
54.7 
0.972 
16 
Venice. 
45 
26 “ 
10 
01 “ 
April 11, “ 
1.129 
63 
21.9 
0.971 
17 
Trieste. 
45 
38 “ 
11 
27 “ 
April 4, “ 
1.128 
63 
20.5 
0.970 
18 
Florence. 
43 
47 “ 
8 
55 “ 
May 28, “ 
1.170 
62 
05.5 
0.965 
19 
Turin. 
45 
04 “ 
5 
20 “ 
June 17, “ 
1.094 
63 
52.2 
0.959 
20 
Rome. 
41 
10 
10 “ 
May 18, “ 
1.225 
60 
14.0 
0.952 
21 
Naples. 
40 
52 « 
11 
57 “ 
May 7, “ 
1.249 
59 
05.1 
0.938 
* Dip not observed. t Mean of results in June, July, and August, 1837, and in July and August, 1838. 
ERRATUM. 
Page 96, (in table,) column headed “No. of Oscillations,” first line, for 150, read 350.