H.. Goldmark—Atmospherie Electricity. 53 
To measure the potential I employed one of Thomson’s 
quadrant electrometers, which was charged sometimes by ‘a 
Holtz machine and sometimes by the Ruhmkorff coil. This 
instrument carries a small concave mirror which reflects a spot 
The method of procedure was as follows: The opposite 
quadrants of the electrometer were connected with two of the 
four binding screws of a peculiar key constructed for the instru- 
ment, while to the other two the wire coming from the measur- 
ing instrument and a wire leading to the earth were respect- 
ively attached. The potential of the air in the drum was then 
measured, the temperature being that of the air of the room. 
The result showed a very constant negative potential, varying 
but little in the successive days on which the experiment was 
made. The potential of the air of the room was also measured 
at the same time, and found to be the same as that of the 
enclosed air, thus proving that the drum had no effect upon 
the electric céndition of its contents. The burners were then 
lighted, and the potential was, from time to time, measured 
after the temperature of the enclosed air, as observed by the 
thermometer ¢, had risen above that outside. 
The change was by no means marked, but I did not on any 
occasion, notice any decrease of potential, but on the contrary 
a small but constant increase on raising the temperature. The 
following table gives some of the measurements m 
April 21. April 24. 25. 
in Potential in 
cee ee ges eer ees Soe 
203 154 23 15 22 164 
30 19 50 204 42 19} 
60 20 67 23 14 204 
88 22 
96 23 
On extinguishing the burners and allowing the enclosed air to — 
cool slowly, it retained the maximum potential it had reached 
on heating, even after it had regained its original low tempera- 
t 
ure, 
Asa result of my experiments I arrived at the following con- 
clusions; Pee 
‘Ist. That, even a very considerable change of temperature, 
does not have any great or marked effect upon the electric poten- 
tial of the air. 
2d. That however a rise in se? yest does produce a slight 
but constant increase in the potentié as, 
