612 
ME. J. HOPKINSON ON THE 
Experiment 0. — The flask was charged for 5 seconds, insulated, and the potential 
read off at intervals of | minutes. The results are the mean of two observations : — 
Reading . . 497 479£ 475£ 474 473 472^ 472|- ■ 
Time ... 0 ^ 1 1|- 2 3 
from this it may be inferred that \|/(0) is considerably greater than 0*07. An experi- 
ment on residual charge gives ^('1) — B=0'017. 
Glass No. 9. — Extra dense flint. Density 3*88. Colour slightly yellow. The pro- 
portion of lead- is somewhat greater than in No. 8. The surface tarnishes slowly if 
exposed unprotected to the air. 
The flask was charged for 10 seconds to 500, and was then insulated. 
After 1 minute the reading was 499 
„ 3 minutes „ „ „ 497f 
30 
60 
59 55 
95 55 
95 95 
59 
„ 495 
„ 486| 
„ 479 
The flask was charged with 48 elements for 1^ hour, and the residual charge 
observed, 
^{2)-B=0-003. 
An attempt was made to obtain a knowledge of the form of the function in the 
same manner as for No. 7. The flask was charged from the electrophorus, and allowed 
to stand insulated for 22 hours ; it was then discharged and temporarily insulated at 
intervals. 
At 
JL 
2 
minute 
traversed 130 
divisions 
in 
^ minute 
= 780 per minute. 
95 
1 
- „ 
59 
160 
55 
59 
i 
3 >5 
o 
GO 
II 
55 
2 
minutes 
99 
145 
95 
99, 
1 
2 y> 
=290 „ 
55 
5 
99 
55 * 
152 
59 
59 
1 „ 
=152 . „ 
5.9 
10 
95 
95 • 
189 
59 
99 
2 minutes 
= 941 „ 
15 
95 
55 
217 
55 
59 
3 „ 
= 72 „ 
55. 
30 
95 
55 
275 
55 
55 
6 „ 
= 46 „ 
55 
60 
„ 
„ 
360 
„ 
59 
12 „ 
= 30 „ 
95 
120 
95 
437 
95 
55 
24 „ 
= 18 „ 
It will be remarked that in this case ^f/(£)— B deviates further from the reciprocal of 
the time than in the case of No. 7. 
Glass No. 10. — Opal glass. This glass is white and opaque. It is essentially a 
flint. The reason for examining it was to ascertain if its opacity had any striking effect 
on its electrical properties. 
