316 Proceedings of Roy cd Society of Edinburgh. [sess. 
quadrant of tlie electrometer in connection with the electric filter, 
and to start working tlie air-pump at the rate of one stroke per 
three seconds. The time of each experiment was ten minutes 
(200 strokes of the air-pump). The results obtained are given in 
the following table. In testing the electrometer matches, four 
matches were stuck in holes in a metallic plate, and the plate con- 
nected hy a wire to the case of the electrometer. These matches, 
according to a suggestion made more than thirty years ago hy 
Faraday, are made of white blotting-paper soaked in a solution of 
nitrate of lead, and rolled up with paste into little rods of about 
five millimetres diameter. The hydrogen was generated in an 
ordinary Woulffe’s bottle from zinc and hydrochloric acid. The 
rise of the dilute hydrochloric acid in the long vertical tube through 
which the acid was admitted, indicated the pressure under the 
nozzle, above which the hydrogen was burning. 
Sensitiveness of the Electrometer 110 scale divisions per volt. 
1. One candle . 
2. One paraffin lamp— 
(a) without glass funnel 
(b) with glass funnel . 
3. One spirit lamp . 
4. Four portable electrometer matches 
5. One Bunsen flame 
6. One hydrogen flame 
Number 
of Experi- 
ments. 
Mean De- 
flection in 
Scale Divi- 
sions of Elec- 
trometer. 
Potential in 
Volts. 
negative. 
negative. 
2 
90 
0-81 
2 
84 
0-76 
2 
30 
0-27 
4 
109 
0*99 
2 
224 
2*03 
4 
30 
0*27 
At low pressure gave small negative ; 
at higher pressures large positive. 
No electrification was found from 
the jet at any pressure when not 
burning. 
7. Charcoal 
8. Coals . 
Both gave negative electrification 
when there was a flame ; and botli 
gave positive electrification when 
they were glowing without flame. 
§ 6. In the case of the charcoal and coal, the burning fuel was 
placed at the bottom of the iron funnel in a thin rectangular 
metallic vessel with small holes perforated in the bottom and in 
the sides. A wire from the case of the electrometer passed through 
