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Transactions of the Canadian Institute. 



[vol. IX 



and a great drop in the upper curve. It will also be seen that the rate of 

 charging of the fatigued electrode as indicated by the lower curves is 

 nearly the same as the final value of the rate of charging of 

 the fresh 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 surround- 

 ed by hydrogen at atmospheric pressure. 



The above experiments therefore shew that a carbon electrode which 

 has been fatigued to 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 is not due to a temporary loss of negative 

 corpuscles which can readily be regained 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 producing secondary rays if 

 it were fatigued for a very short time only. A fresh piece of carbon was 

 placed in the apparatus and a set of experiments similar to the ones de- 

 scribed 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 sur- 

 rounded by air at atmospheric pressure are given in Table XI. 



Table X. 



