328 Prof. J. J. Thomson, On the Effect of Pressure and [Jan. 28, 
density diminishes, in order to see whether the diminution of the 
strength caused by the increase of temperature could be accounted 
for by the rarefaction of the gas. I repeated the experiments 
on H .CO, and air, when the gases were sealed up in tubes, 
so that the density could not alter; from the following results it 
will be seen that the electric strength under these circumstances 
1s practically constant, so that at temperatures between 15° and 
300° C. the electric strength only depends on the number of 
molecules in unit volume. 
Air at constant density. 
Temp. Air space. 
10 ler 
20 17 
35 a 
50 NG 
60 Lg 
70 ila 
80 17 
100 16°5 
120 165 
140 16°5 
160 16°5 
180 16°5 
200% 165 
Another tube. 
Temp. Air space. 
18 
AO 
65 
100 2 
120 2°5 
140 25 
170 2°5 
200 3° 
CO, at constant density 
Temp. Air space. 
Uy 2 
35 15 
65 15 
90 15 
140 15 
160 15 
185 15 
200 ?. 
