41 
1897-98.] Leakage from Electrified Metal Plates. 
potential into time should be constant for the same deflection from 
metallic zero. Taking the numbers obtained for the 300 scale 
divisions of deflection in virtue of the Bunsen flame, we have : — 
Positive Charge. 
Negative Charge. 
V. 
s. 
V. 
s. 
9'5 x 
108 = 
1026 
95 x 
48 = 456 
135 x 
72 = 
972 
13 5 x 
30 -- 405 
16-5 x 
46 = 
759 
16-5 x 
18 = 297 
28*5 x 
15 = 
427 
28*5 x 
13 = 370 
44-5 x 
11 = 
489 
44‘5 x 
8 = 356 
72’5 x 
6*5 = 
•471 
72*5 x 
5 = 362 
91-5 x 
5 = 
457 
91-5 x 
4 = 366 
Thus it is proved that the leakage between two plates, each 10 
square centimetres in area, 1 centimetre apart when the fumes 
from a Bunsen burner pass between them and round them, is 
approximately proportional to the difference of potential between 
them, when that difference is above 20 volts and up to 94 volts, 
the highest we have tried ; but that, below 20, it diminishes with 
diminishing voltages more than according to simple proportion. 
§ 4. To determine the currents which we had in our arrangement, 
we took a movable plate of a small air condenser charged to a 
known potential, and applied it to the insulated terminal of the 
quadrant electrometer. In this way we found that a quantity 
equal to 0*15 electrostatic unit, gave a deflection of 300 scale 
divisions. Hence in the experiments with the Bunsen flame and 
with a potential of - 94 volts kept on the uninsulated copper plate, 
the current to the insulated copper plate opposite to it, when 300 
scale divisions was reached in five seconds, was— 
0*15 
g -^9 x 4= 10- 11 ampere. 
= — - — mikro-ampere. 
100000 * 
§5. One of us about the year 1865, when occupied in ex- 
perimenting with the latest form of portable electrometer, found 
that if it was held with the top of its insulated wire (which was 
about 33 centimetres long) a few inches below a gas-burner, a 
charge of electricity, whether positive or negative, given to this 
wire was very rapidly lost. The disinsulating power of flames and 
of hot fumes from flames was well known at that time, but it was 
surprising to find that cold air flowing up towards the flame did 
somehow acquire the property of carrying away electricity from a 
