RESIDUAL CHARGE OF THE LEYDEN JAR. 
607 
Experiment s. — The flask was for many hours charged negatively, then positively for 
5 minutes, and observations of residual charge were made as before. 
doc 
Column III. are the values calculated from y by the formula 2\f/(T + tf). 
I. 
II. 
III. 
i 
— 310 
-301 
1 
-168 
-154 
2 
- 48 
- 44 
4 
+ 8 
+ 6 
5 
+ 17 
+ 16 
10 
+ 28 
+ 27 
15 
+ 27 
+ 28 
20 
+ 27 
+ 27 
Glass No. 3. — Common window-glass, composed of silica, soda, and lime, the quan- 
tity of lime being greater than in No. 2. This glass does not “ sweat ” in a moist atmo- 
sphere. The temperature was 68° F. 
Experiment a. — The flask was charged to 425 divisions for about 3^ hours, and was 
then insulated. After \ minute the charge was 210; 1 minute, 138; 2 minutes, 74; 
3 minutes, 50. Hence B is certainly greater than unity, and lies intermediate between 
the values for glasses 1 and 2. 
Experiment y gives the observed values of ^p(t) — B throughout a little less than in 
No. 2. As this flask was not very well blown further experiments were not made. 
If the values of — B could be accurately obtained for these three glasses, they 
would certainly differ less from each other than they appear to do. 
Glass No. 4. — Optical hard crown. Density 2-48. Composed of silica, potash, and 
lime. The composition may be regarded as corresponding to a glass intermediate 
between 1 and 3, with the soda replaced by potash. 
The experiments a and f3 were made by the following modified method :• — ' The whole 
battery of 48 elements was used, one pole being connected with the case of the electro- 
meter and the exterior of the flask, the other with the interior of the flask by a cup of 
mercury and also with one electrode of the electrometer. The other electrode was per- 
manently connected with the interior of the flask. It was ascertained that the image 
remained at zero whether both quadrants were charged equally or both discharged. 
The potential of the 48 elements was measured by 6 elements at a time ; the extremes 
were 432 and 437, and the total 3475 scale-divisions. Where the charge of each 
MDCCCLXXVII. 4 R 
