422 MR. DTTGALD M‘KICHAN ON THE DETERMINATION OF THE NUMBER 
Temp. 17° C. September 12, 1871. Battery 90 cells. 
Electrometer. 
Electrodynamometer. 
Resistance in B. A. 
units. 1 = 10° centims. 
per second. 
v in centims. per 
second. 
Difference. 
36-25 
36-25 
36-25 
36-3 
Mean. 
36-25 
36-27 
Deflection. 
R. 647-5 
L. 647-5 
R. 646-75 
L. 646-75 
Mean. 
647-5 
646-75 
15960 
298-8 x 10 s 
298-5 x 10 8 
September 16, 1871. Battery 90 cells. 
Electrometer. 
Electrodynamometer. 
Difference. 
Mean. 
Deflection. 
Mean. 
35-1 
35-1 
35-1 
It. 608-5 
L. 613-5 
611-0 
35-6 
34-4 
35-0 
R. 602-5 
L. 600-5 
601-5 
34-3 1 
R. 616-0 
614-5 
34-8 1 
34-8 
L. 613-0 
35-25 J 
R. 615-5 
615-0 
36-6 
36-0 
35-5 
35-7 
L. 614-5 
35-4 
35-4 
35-55 
35-6 
35-8 
R. 613-5 
L. 613-5 
R. 613-5 
L. 615-0 
613- 5 
614- 25 
Resistance in B. A. 
units. 1 = 10 ;) centims. 
per second. 
v in centims. per 
second. 
(15960) 
assumed from 
former 
measurements. 
299*8 x 10 s 
298-3 X 10 8 
303-9 X 10 s 
293-2 X 10 8 
297-Ox 10 3 
295-5 X 10 8 
A considerable degree of uncertainty attaches to the foregoing results on account of 
their variations amongst themselves, and also because an independent determination of 
the resistance of the coils was not made. The variations are due chiefly to variations 
in the electrometer readings, to which there was the greater liability on account of the 
smallness of the difference of potentials measured. A battery of 90 cells was employed, 
no additional resistance having been introduced into the circuit. 
In the series which follow a continuous measurement of resistance was made. The 
same battery was used, but the differences of readings in the electrometer show less 
variation among themselves. The period of vibration of the coil was 5-811 seconds, 
and the corresponding value of y -00002015. 
