﻿&2G Mr. V. E. Pound on the Secondary Bays 



Table VI. 



Air in Apparatus. 



Fatigued carbon electrode. Charge on polonium — SO volts. 



Pressure of air in 

 vessel. 



•008 mm. 



•003 „ 



•002 „ 



•001 „ 



■<-ooi „ 



Time from initial 



reading taken 7 minutes 



after starting pump. 



Current to 

 electrode. 



minutes 

 5 



15 „ 



36 



60 „ 



327 



302 

 29-2 

 24-7 

 223 



After this experiment was completed the apparatus was 

 immediately filled with air at atmospheric pressure and left 

 standing for 22 hours. Then the above experiment was again 

 repeated with the following results. 



Table VII. 



Air in Apparatus. 



Fatigued carbon electrode. Charge on polonium =80 volts. 



Pressure of air in 

 vessel. 



Time from initial 



reading taken 7 minutes 



after starting pump. 



Current to 



electrode. 



•004 mm. 

 •001 „ 

 <-001 „ 



minutes 

 5 „ 

 22 



25-3 



22-8 

 21-8 



The results given in the last two columns of Tables V.— VII. 

 are represented by curves shown in fig. 4. The upper curve 

 is plotted from the results given in Table V., the middle 

 curve from Table VI., and the lower curve from Table VII. 



It will be seen on looking at the curves that each has a 

 gradual drop. This drop represents both the decrease as 

 time went on in the rate at which the carbon electrode sent 

 out secondary rays, and the decrease in the ionization current 

 across the air-gap between the polonium and the electrode, 

 beginning at a certain definite interval of time after the first 

 air was taken from the apparatus. It will be seen also on 

 comparing the curves that the initial point of the upper 

 curve is much higher than the initial points of the lower 

 curves. Also the upper curve decreases much more quickly 

 than the lower curves, until, finally, the three curves all come 



