OBSERVATIONS OF THE MAGNETIC FORCE. 
289 
tion of m and X (the values of the magnetic moment of the deflecting magnet and 
of the horizontal component of the force). The values of the absolute horizontal 
force are expressed in the units directed in the Report of the Committee of Physics 
of the Royal Society, 1840, pp. 21, 22. These values may be converted into their 
equivalents in the scale more frequently employed by the continental magneticians, 
hy being multiplied by the factor 0’4609. 
Table XXX. — Abstract of the observations to determine the absolute value of the 
horizontal component of the Magnetic Force with a German transportable magne- 
tometer. 
Angles of deflection. 
Corrected 
Temperature. 
Values of m. 
X. 
t 
Date. 
Station. 
Bar. 
time of one 
( 
u. 
u'. 
u". 
vibration. 
Deflection. 
•Vibration. 
N. 13. 
N. IX. 
Observed. 
Mean. 
1842. 
380 
30-3 
O 
42-6 
169 
n 
27-6 
40-6 
s 
Sept. 7. 
Quebec . . . -j^ 
N. IX. 
N. 13. 
11 
12 
7 
8 
4 
4 
6- 929 
7- 137 
62 
62 
62 
63 
•798 
•756 
3045 1 
3-035 J 
3040 
Near theR. A. Barracks 
16. 
Montreal ... 
N. 13. 
11 
54-9 
7 
48-1 
4 
230 
7-201 
62 
62 
■776 
3-064 
3 064 
St. Helen’s, [tanville. 
25. 
New York . . . 
N. 13. 
9 
17-8 
6 
08-2 
3 
273 
6-286 
55 
58 
•779 
4-008 
4008 
Lun. Asylum, Manhat- 
Oct. 1. 
Cambridge 
N. 13. 
N. IX. 
10 
9 
02-2 
30-3 
6 
6 
38-1 
16-7 
3 
3 
44-8 
38-7 
6-598 
6-364 
72 
65 
65 
72 
•774 
•744 
3-662 
3-669 
3-665 
Magnetic observatory. 
13. 
Philadelphia 
N. 13. 
8 
48-3 
5 
49-5 
3 
175 
6163 
55 
51 
•778 
4176 
4176 
Magnetic observatory. 
Nov. 12. 
Chicago* | 
N. 13. 
N. IX. 
9 
8 
04-3 
29-8 
6 
5 
00-3 
351 
3 
3 
23-5 
15-4 
6-765 
6-752 
29 
35 
43 
28 
•788 
•731 
4106] 
4105 j 
4-106 
Oct. 28. 
Toronto f 
N. 13. 
10 
23-8 
6 
52-8 
3 
53-4 
6-718 
50 
50 
•775 
3-529 ] 
N. IX. 
9 
38-6 
6 
27-3 
3 
44-2 
6-509 
50 
51 
>> 
•745 
3-501 
3-532 
Dec. 19. 
1843. 
Mar. 25. 
Toronto ... 
N. 13. 
10 
22-5 
6 
52-6 
3 
53- 1 
6-680 
33 
32 
•779 
3-547 
N. IX. 
9 
44-7 
6 
27-9 
3 
44-2 
6-492 
32 
33 
•738 
3-552 j 
Magnetic obser- 
Toronto 
N. IX. 
9 
17-3 
6 
11-3 
3 
34-6 
6-633 
46 
45 
•712 
3-5261 
vatorv. 
Mean 3-5365. 
27. 
Toronto 
N. IX. 
9 
21-9 
6 
12-4 
3 
35-3 
6-621 
42 
42 
•711 
3-545 
28. 
Toronto 
N. IX. 
9 
190 
6 
10-7 
3 
34-2 
6-623 
49 
46 
>> 
•710 
3-551 
3-541 
Mar. 25. 
Toronto 
N. 13. 
10 
15-4 
6 
47-4 
3 
50-1 
6-730 
46 
45 
•768 
3-546 
J 
27. 
Toronto 
N. 13. 
10 
15-9 
6 
47-9 
3 
50-4 
6-725 
42 
41 
•772 
3-536 
28. 
Toronto 
N. 13. 
10 
18-0 
6 
49-1 
3 
50-8 
6-722 
48 
47 
•770 
3-541 J 
“ I proceed to the observations of absolute horizontal force made subsequently 
to March 1833 with a portable unifilar magnetometer, constructed on the principle 
proposed by Dr. Lamont, in which the deflecting bar is retained at right angles to 
the suspended bar, and the angles of deflection are read off upon the graduated circle 
of the base. The lengths of the suspended and deflecting bars were in the ratio of 1 
* The observations at this station were made by Lieut. Younghusband, R.A. The bar was vibrated in a 
different stirrup from that commonly employed, and its moment of inertia was afterwards ascertained at Toronto, 
by vibration of each bar with and without weights: the following were the dimensions; /= 3'755 inches; 
r=0’4095 inches; y>=418'0 grains; whence K l =(jtfi + r‘ i )p=20'594 ; and the following were the resulting 
values of log ir 2 K, by a single set of vibrations with each bar : N. IX. = 213194 ; N. 13. = 2-17200. 
t The observations at Toronto in 1842 have been already published in the Toronto volume for 1840-42. 
The series in March 1843 was observed by Lieut. Younghusband. The horizontal intensity at Toronto 
having since been determined with superior instruments, these results are principally interesting for compa- 
rison with those obtained at other stations. 
