﻿830 Mr. V. E. Pound on the Secondary Rays 



electrode as indicated by the upper curve. Hence the 

 above experiments indicate that the carbon electrode did not 

 regain any of its primary power of producing secondary 

 rays by being surrounded by hydrogen at atmospheric 

 pressure. 



The above experiments, therefore, show that a carbon 

 electrode which has been fatigued in the production of 

 secondary rays, and left in vacuo for a long time, will not 

 regain its primary power of producing secondary rays by 

 simply being placed in an atmosphere of either air or 

 hydrogen. Hence the fatigue of the carbon was not due to 

 a temporary loss of available negative corpuscles, which 

 might possibly be regained in some way from air or hydrogen 

 when these gases are allowed to surround the carbon. 



The next experiments that were tried were to find out 

 whether a piece of carbon would regain its power of pro- 

 ducing secondary rays if it were fatigued for a very short 

 time only. A fresh piece of carbon was placed in the appa- 

 ratus and a set of experiments similar to the ones described 

 above was performed, except that, instead of leaving the 

 carbon in the evacuated chamber after the current to the 

 carbon had gained a steady value, it was left for a week 

 with the air at atmospheric pressure. The readings taken 

 with the fresh carbon are given in Table X., and the readings 

 taken after the fatigued carbon had been left for a week 

 surrounded by air at atmospheric pressure are given in 

 Table XL 



The results given in these two Tables are graphically illus- 

 trated by the curves shown in fig. 6. The upper curve refers 



Table X. 



Fresh carbon electrode. 



Air in apparatus. Charge on polonium = 82 volts. 



Pressure of air in 



vessel. 



Time from initial 



reading taken 7 minutes 



after starting pump. 



Current to 

 electrode. 



•008 mm. 

 •003 „ 



•ooi „ 



•001 „ 



<-ooi „ 

 <-ooi „ 

 <:-001 ., 

 <-001 „ 



minutes 



5 „ 



15 



oO 



60 



90 



120 



142 



1235 

 82-5 

 44-5 

 29 

 22 

 19-5 

 18 

 17 5 



