92 Mr. McClung on the Effect of Temperature on the 
In taking the observations the rays were started and 
allowed to run for a definite number of seconds, so that the 
ionization might reach a steady state, both the electrodes H 
and I being to earth during this time. At the end of this 
interval the electrode E was insulated and the key W opened 
simultaneously, and the rays were allowed to run for a given 
time. The electrodes E and I were thus allowed to charge 
up for exactly the same time, and under the influence of 
the same cone of rays. The reading of the electrometer 
corresponding to the charge on E was’ observed, and then 
the quadrants of the electrometer were discharged and again 
insulated, and the key W was then closed and the deflexion 
corresponding to the charge on I observed. ‘This served 
therefore as a very close check on the constancy of the rays 
during exactly the same time as the measurements were being 
made in the cylinder AB. 
The first gas tested with this apparatus was of course air, 
in order to see if the results would be in agreement with 
the previous experiments. Observations were taken over a 
range of temperature of nearly 200°C., and the results 
obtained exactly confirmed the previous results which I had 
obtained. In this case when the density of the air was kept 
constant, the amount of ionization also remained constant. 
The change of temperature of the air had no effect whatever 
upon the amount of ionization produced in it. A set of 
results obtained is shown in Table II. as a specimen. 
TAsi EOL Aw 





Ionization as represented | Ionization as represented | Temperature of 
by Scale-Divisions for | by Scale-Divisions for Air in 
the Cylinder AB. | Standard Apparatus. Cylinder AB. 
83°7 27-0 201°C 
| 86°5 | 30°35 152° 
82'8 re Gt | 118° 
85°8 | 315 | 87° 
80-4 | 28-5 45° 
83°2 | 28°95 14° 

From the results obtained therefore by the two methods 
there appears to be no doubt whatever that, when the density 
of a given volume of air is kept constant, the amount of 
ionization produced in it per second by rays of a given 
intensity is quite independent of the temperature of the air. 
ad 
