CAPACITY AND RESIDUAL CHARGE OF DIELECTRICS. 
121 
from 21° to 122°, but here the sensibility was not so good as with the higher 
frequency. We conclude that the apparently great capacity of this glass at a 
temperature from 120° to 170° is due to residual charge, but that the effects of this 
part of the residual charge are not greatly felt if the frequency is greater than 
about 10,000 a second. 
The extent to which the capacity of the window-glass flask is affected by the 
frequency at ordinary temperatures, 8° C., is shown by the following figures :— 
Frequency .... 12 39 70 
Capacity.'00075 '0008 '001 
Table IV. 
20th November, 1894. 
Frequency, 72 ; volts, 70. 
21st November, 1894. 
Frequency, 85|; volts, 71^. 
26tli November, 1894. 
Temperature, 120° C. 
Tempera¬ 
ture. 
C. 
Capacity of 
flask in 
terms of itself 
at 1.5°. 
Tempera¬ 
ture. 
C. 
Capacity of 
bask in 
terms of itself 
at 25° C. 
Frequency. 
R./Ri. 
Remarks. 
L”) 
1 
2.54 
1 
7-3 
1-27 
Standard conden- 
92 
1-31 
54 
1-05 
12 
111 
ser unaltered 
117 
l-()6 
9.5 
1-27 
394 
•87 
throughout ex- 
l.")4 
2-6 
120 
1-.59 
7U 
•78 
periment 
170 
2-61 
100 
•75 
Conductivity after Electrification for Short Times. 
The Battery. —This consists of 12 series of small storage cells, fig. 5, each series 
containing 50 cells. The poles of each set of 50 cells are connected to mercury 
cups in a paraffin block, and numbered 1, 3, 5, . . . 21, 23, on the positive side; 
2, 4, 6, . . . 22, 24, on the negative. Cups h, d, are connected to the poles of the 
56 cells in the Laboratory, and therefore, by connecting d, 1, 2 . . .21, 23, together 
on the one side, and 2, 4, . . . 22, 24, h, together on the other side, the cells can 
be charged in parallel. For the purpose of these experiments, a large potential 
difference is required ; this is obtained by removing the charging bars, and replacing 
them by a series of conductors connecting a; to 1, 2 to 3 . . . 22 to 23, 24 to y. In 
this manner, the whole of the 600 cells are placed in series with one another. 
Across the terminals x, y, are placed a condenser Kg of about 4'3 microfarads, and a 
Kelvin vertical electrostatic voltmeter V. In order to change over quickly, and for 
the purpose of safety, the charging bars and connections for placing the cells in series 
are mounted on wood. 
MDCCCXCVIl,—A. 
R 
