TEMPERATURE COEFFICIENT OF THE BALANCE MAGNET. xiii 
Taste 14.—Observations for the Temperature Coefficient of the Deflection Magnet. 
Reading Biflar. 
Gottingen Tempera- Reading jof Declino-| u—wp ¥ Correction 
Mean Time, ture of to — te 0 meter enna 9) |S ei eed AOE abr. 
Magnet. Unifilar. | reduced | f(d—d)).| Reading | Thermo- =i 
= fide Corrected.| meter. 
° SI Se. Diy. Se. Div. Se. Diy. Se. Diy. 
Magnet | away. 264-39 | 157-26 
35:30 10-73 | 156-65 501-0 
Nov. 11 0 59-05 | 266? | 1205 | 15617 | 1" 501-7 aed 
76:85 = 13-07 | 155-59 502-7 S 
S 17-90 : -000278 
58-95 e 11-88 | 155-63 503-3 : 
22-05 . -000309 
36-90 10-05 | 155-49 503-9 : 
20-20 a -000289 
57-10 11-68 | 155-64 504-3 : : 
is 21-60 < -000260 
78-70 13-16 | 155-67 505-6 . 
22-20 : -000272 
56-50 11-11 | 155-13 505-8 . 
19-90 a -000265 
36-60 10-05 | 155-36 506-8 . 
20-30 = : -000253 
56-90 25.05 11:50 | 155-50 , 507-4 ‘ 000307 
81-95 21-05 13-41 | 155-50 : 506-8 . .000233 
60-90 2 | 12:50 | 155-80 507-4 . 
24-05 = = : -000268 
36:85 10-78 | 155-69 507-7 : 
30-50 : -000287 
67-35 13-30 | 156-00 508-0 . 
23-40 -000324 
43-95 99.55 11-72 | 156-33 ’ 507-8 : .000315 
66-50 13-88 | 156-70 508-1 
Magnet | away. 264-35 | 157-02 
0 
0 
1 
1 
1 
2 
2 
2 
2 
3 
3 
3 
4 
4 
4 45 
The mean value of g = 0:0002877. 
Balance Magnet. 
61. The value of the coefficient for the balance magnet was obtained by obser- 
vations, similar to those for the deflecting magnet, on 5 different days ; weight was 
given to the result of each day’s observations, depending on the formula, No. 32. 
The final result was 
= 0:000073.* 
62. The impossibility of determining the value of the micrometer divisions of 
the balance magnetometer by the usual method has been already pointed out. It 
is obvious, therefore, that if shut up to this method the temperature corrections 
cannot be applied even when the observations are left in the state of micrometer 
divisions. The doubt whether the changes of the magnetic moment of the needle 
occur as rapidly as those of temperature in all cases, and therefore, whether a co- 
efficient obtained from changes of 30° or 40° in a few minutes (as in the tempera- 
ture experiments) was likely to be applicable to observations where the changing 
temperature of the needle was rarely above 1° in the hour, and the fact that other 
sources of error (perhaps the effect of temperature on the points of support of ‘the 
* Tables 19 and 20, Introduction to the Makerstoun Observations, 1841 and 1842. 
