424 ME. DUGrALD M‘IvICHAN ON THE DETERMINATION OE THE NUMBER 
September 28, 1871. Battery 90 cells. 
mometer. 
Resistance in B. A. 
units. 1=10 9 centims. 
per second. 
v in centims. per 
second. 
Mean. 
536*5 
15715 
292*0 x 10 s 
5°8*0 
15715 
294*6 x 10 s 
518*25 
15711 
291*6 x 10 s 
519*25 
15722 
293-7 X 10 s 
Electrometer. 
1 
Difference. 
33-2 
33-5 
32-851 
32- 8 
32*5 
33- 0 
32*7 
33-1 
32-7 
32-8 
32*75 
32-6 
32*5 
32*4 
32*8 
32*8 
32*5 
32*8 
Mean. 
33*35 
32*79 
32*81 
32*63 
Deflection. 
R. 536*5 
L. 536*5 
L. 529*5 T 
> 
R. 526*5 J 
L. 51 8*25 
R. 518*25 
R. 520*0 1 
L. 518*5 
No further comparisons were made till February 21, 1872. In the series of observa- 
tions then taken, to secure a greater difference of readings in the electrometer, a larger 
battery was employed, and a resistance of 10,000 ohms was introduced into the circuit. 
The difference of potentials between the ends of the coils was thus = — — — — . e. where 
e represents the difference of potentials read off in the electrometer, and Ii is the resist- 
ance of the electrodynamometer circuit. 
The scale was removed to a greater distance, 367*9 centims., and the period of vibra- 
tion of the coil was 5*819 seconds. The corresponding value of y was *000019761. 
The resistance of the coils at the observed temperature was afterwards measured and 
found to be 15834 B. A. units. This value of R is used in the calculations. 
Temp. 15° C. February 21, 1872. 
Resistance in B. A. 
v in centims. per 
second. 
Electrometer. 
Electrodynamometer. 
units. 1 = 10° centims. 
per second. 
Difference. 
Mean. 
Deflection. 
Mean. 
58*0 
58*00 
R. 630*5 
L. 633-5 
632*00 
15834 
293*4 x 10 8 
58*1 
58*1 
58*10 
L. 636-0 
R. 633*5 
L. 638*25"| 
634*75 
293*5 x 10 8 
58-2^ 
> 
58*25 
R. 634*5 > 
L. 6,34*0 J 
636-19 
293*1 X 10 8 
58*3 J 
R. 634*0 5 
L. 638*0 }■ 
636*12 
292-3 X 10 8 
58-4 
R. 634*25 J 
58*2 
R. 635*0 
L. 638*25 
636-62 
293*5 X 10 s 
58*2 
L. 638*5 
R. 635*0 
636*75 
293*5 x 10 8 
