454 
PEOFESSOE W. WATSON ON A DETEEMINATION OF THE VALUE OF 
The following table contains a summary of the results obtained. The value of H 
given in the twelfth column is derived from the reading of the recording magneto¬ 
graph, the value of the base line of the trace being deduced from the sets of absolute 
measurements made with the Observatory standard instruments, by the Observatory 
staff, during January and February, 1901. The values of H obtained wdth the coil 
when using the shorter of the two magnetic needles, which are indicated by an S 
placed in the ninth column, have been corrected for the inclination of the magnetic 
axis of this needle. That is, the values of H have been multiplied by cos 38'. This 
reduces the value of H by 0'000012. 
In obtaining the value of TI, given in this table, the same values for the resistance 
of the coils have been used as were employed in deducing the E.M.F. of the cadmium 
cells in the talJe on p. 455. Also the mean value of the E.M.F., as deduced from 
the llayleigh voltameter there given, was used as corresponding to the E.M.F. of 
the cell at 20° C. Hence the value of H given does not depend in any way on the 
absolute value of the resistances, or of the E.M.F. of the cadmium cell, but only on 
the value assumed for the electro-chemical equivalent of silver, wJrich was taken 
as O'OOlllS in the case of the Rayleigh form of voltameter. 
Column 1 contains the number of the experiment, col. 2 the date, 3 the time, 
4 the temperature of tlie cadmium cell, 5 the temperature of the resistance coils, 
6 the temperature of the Helmholtz galvanometer, 7 the number of cadmium cells 
which were included in the potential circuit, 8 the numbers of the resistance coils 
between the terminals of which the difference of potential was adjusted to balance 
the E.M.F. of the number of cells given in column 7, 9 the deflection of the 
Helmholtz galvanometer, 10 the value of H deduced from the galvanometer 
deflection, 11 the value of H as obtained from the magnetograph trace, and 12 the 
difference between the values of H given in the two preceding columns. 
1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 
10. 
11. 
12. 
1 
1901. 
Feb. 4 
h m. 
15 25 
o ^ 
17-3 
o 
o • 
“ 0. 
11 
1 
2 + 3 
23 12 45 
T8443 
•18441 
•0000 i 
+2 
2 
5) 
15 35 
17-2 
11-5 
11 
1 
2 + 3 
23 12 54 
T8440 
•18439 
+ 1 1 
3 
15 46 
17T 
11-6 
12 
1 
2 + 3 
23 12 47 
T8441 
•18440 
+ 1 
4 
15 55 
17-0 
11-6 
12 
1 
2 + 3 
23 12 36 
T8443 
•18440 
+ 3 
5 
16 1 
17-0 
11-8 
12 
1 
2 + 3 
23 12 39 
T8442 
•18441 
+ 1 
6 
Feb. 5 
12 29. 
19-5 
11-3 
14 
1 
2 + 3 
S 23 12 29 
•18441 
•18440 
+ 1 
7 
3) 
12 38 
19-5 
11-8 
14 
1 
2 + 3 
S 23 12 21 
■18443 
•18441 
+ 2 
8 
33 
13 44 
19-9 
14-6 
18 
1 
2 + 3 
S 23 11 28 
•18447 
•18446 
+ 1 
9 
33 
13 52 
19-8 
14-8 
18 
1 
2 + 3 
S 23 11 31 
•18446 
•18446 
+ 0 
10 
33 
14 0 
19-8 
14-8 
18 
1 
2 + 3 
S 23 11 28 
•18447 
•18445 
+ 2 
11 
33 
14 6 
20-3 
15-0 
18 
1 
2 + 3 
S 23 11 32 
•18445 
■18444 
+ 1 
12 
33 
14 22 
20-4 
15T 
18 
1 
2 + 3 
23 11 45 
•18443 
•18444 
- 1 
13 
33 
14 32 
20-5 
15-2 
18 
1 
2 + 3 
23 11 40 
•18443 
•18443 
+ 0 
14 
33 
14 41 
20-5 
15-4 
18 
1 
2 + 3 
23 11 39 
•18443 
•18444 
- 1 
15 
33 
14 48 
20-4 
15-4 
19 
1 
2 + 3 
23 11 34 
•18443 
•18444 
-1 
16 
33 
14 55 
20-3 
15-5 
19 
1 
2 + 3 
23 11 32 
•18443 
•18444 
-1 
