610 
MR. J. HOPKINSON ON THE 
I. 
II. 
III. 
IV. 
V. 
VI. 
VII. 
i 
JL 
CO 
1 
37 
222 
252 
i 
X 
3 
42 
43 
42 J 
127-5 
124 
2 
i 
32 
32 1 
32| 
64-5 
72 
5 
l 
23 
22 1 
22| 
22-75 
24 
15 
4 
23 
23 
5-75 
4-25 
The differences between VI. and VII. are somewhat large ; they may perhaps be in 
part attributed to the fact that is deduced from observations on a quantity not uni- 
formly increasing, on the assumption that the increase is uniform, and to the inequality 
of the times of insulation. 
Glass No. 6. — A flint glass containing less lead than No. 7. 
Experiments a and /3. — 66 divisions of the scale equal to one Daniell’s element. 
The flask was continuously connected with the battery, and only insulated for brief 
periods, to determine the rate of loss, the following values are thence deduced : — 
t. . . 
5. 
15. 120. 
240. 
m- 
. . . 0-013 
0-007 
0-004 0-0016 
0-001 
Experiment y.- 
— The flask was 
charged for 
13 hours with 48 elements, then 
discharged. 
The columns are the same as 
in glass No. 
5. 
I. 
II. 
III. 
IV. 
V. 
1 
21 
i 
¥ 
63 
0-02 
5 
37± 
2 
18*75 
0-006 
15 
48 
6 
8-0 
0-0026 
75 
60 
24 
2-5 
0-0008 
There is a considerable discrepancy between the values of 4/(1} from a and 4(1) — B 
from y ; the former may be in error, as it was deduced from the time of traversing 
3 divisions only. 
Glass No. 7. — Optical “light flint.” Density 3-2. Composed of silica, potash, 
and lead Almost colourless. The surface neither “sweats” nor tarnishes in the 
slightest degree. This glass at ordinary temperatures is sensibly a perfect insulator. 
A flask was mounted in the usual way on July 15th ; it was charged with 48 elements 
for some hours, the potential being 240 scale-divisions as measured through the 
“ induction-plate ” of the electrometer. The charging-wire was then withdrawn. On 
July 23rd the wire was again introduced and connected with the induction-plate; a 
charge of 183 scale-divisions still remained, although the temperature of the room 
