i6o 



Transactions of the Canadian Institute. 



[vol. IX 



under the same conditions. Accordingly the brass electrode was re- 

 moved from the apparatus and a similar shaped piece of carbon was put 

 in. The polonium was charged to a positive potential of 78 volts, and 

 the pump was started exhausting the air which was initially at atmos- 

 pheric pressure. Seven minutes after the pump was started readings 

 were taken of the pressure of air in the vessel as measured b}^ the McLeod 

 gauge, and the rate of charging of the carbon electrode. Similar read- 

 ings were made at different intervals of time after the initial readings. 

 The pump was kept going continuously throughout all the readings. 

 The results are given in the following table. 



Carbon Electrode. 



Table IV (a) 



Air in Apparatus. 



Charge on Pol. = 78 volts. 



The pump was then stopped and while the pressure gradually in- 

 creased as the air flowed out from the walls of the apparatus, the series 

 of readings were continued and are given below. 



Table IV (ft). 



