OF ELECTEOSTATIC UNITS IN THE ELECTROMAGNETIC UNIT. 
419 
oft' on the electrodynamometer scale, the mean between these two deflections was taken 
as representing Avhat would have been the deflection supposing that the process of eli- 
minating the horizontal component of the earth’s magnetism had been perfectly success- 
ful. These deflections are noted as R. and L. (right and left) with reference to the 
sides of the battery-key. Corresponding to each, two readings were obtained in the 
absolute electrometer by reversing the electrometer-key while the battery-circuit con- 
tinued “ made,” half the difference of readings due to this reversal representing the dif- 
ference of potentials between the two ends of the coils through which the current was 
passing. 
It was found, however, in most of the comparisons, that the current corresponding 
to a difference of potentials sufficiently large to be measured on the electrometer with 
a small percentage of error, produced a deflection in the electrodynamometer beyond 
the limits of the scale. 
In order to reduce the strength of current without at the same time reducing the 
difference of potentials to be measured by the electrometer, a large resistance (R), gene- 
rally equal to that of the circuit formed by the coils, was introduced between the coils and 
the battery, and the difference of potentials between one extremity of this interpolated 
resistance and the remote end of the coils was observed. From this the difference of 
potentials between the two ends of the coils was immediately deducible. 
Temp. 8 0, 2 C. March 11, 1870. Battery 180 cells. 
Resistance in B. A. 
v in centims. per 
second. 
Electrometer. 
Electrodynamometer. 
units. 1 = 10 9 centims. 
per second. 
Difference. 
Mean. 
Deflection. 
Mean. 
63-3 
63*1 
63-2 
R. 420-5 
L. 421-0 
420-75 
15587 
293-Ox 10 s 
63*4 
63-4 
63-4 
L. 420-5 
R. 420-5 
420-5 
(15597) 
292-2 X 10 s 
63-1 
63-3 
63-2 
L. 420-0 
R. 419-0 
419-5 
15607 
292-3 x 10 s 
Temp. 9°'4 C. March 15, 1870. Battery 180 cells. 
Electrometer. 
Electrodynamometer. 
Resistance in B. A. 
units. 1 = 10 9 centims. 
per second. 
v in centims. per 
second. 
Difference. 
61-5 
61- 4 
61-8 
62- 0 
61-7 
61-4 
Mean. 
61-45 
61-90 
61-55 
Deflection. 
R. 412-0 
L. 408-5 
R. 410 0 
L. 408-5 
R. 409-0 
L. 407-5 
Mean. 
410-25 
409-25 
408-25 
15555 
297-0 xlO 8 
294- 5 x 10 3 
295- 8 x 10 3 
3 i 2 
