﻿823 



excited hy the Alpha Rays from Polonium. 



If the results that were obtained while the pressure of the 

 air was decreasing are compared with the results obtained 

 while the pressure was increasing, as given in Table IV., and 

 shown graphically in fig. 3, it will be seen that at any given 



Fio-. 3. 



.032 



.024 .016 .008 



Pressure in mms of Hy. 



pressure the rate of charging of the electrode was greater as 

 the pressure was decreasing than as it was increasing. It 

 will also be seen that the rate of charging at a pressure of 

 *035 mm. of mercury as the pressure was increasing was 

 very much less than the rate of charging at much smaller 

 pressures as the pressure was decreasing. These results show 

 clearly then, that the decrease in the rate of charging of the 

 electrode as the air was pumped out of the apparatus was 

 not all due to a decrease in the ionization current through 

 the gas. For since the ionization current is only dependent 

 on the pressure of the air in the chamber, it should have the 

 same value at like pressures, whether the pressure was 

 decreasing or increasing. 



If the decrease in the rate of charging of the electrode 

 with the time was not all due to a decrease in the ionization 

 current through the gas there must be some other reason for 

 this decrease. As shown in § 3, there are three other 

 currents which cause the electrode to charge up besides the 



