568 Dr. H. Stanley Allen on the 



2. Fatigue independent of the Electric Field. 



The rate at which fatigue takes place does not depend on 

 the strength of the electric field applied. This is illustrated 

 in Table IV., which contains results of experiments made in 

 the air of the room and of others made in the brass testing 

 vessel. The zinc plate used was polished with fine emery- 

 paper. 



Table IV. 

 Zinc plate. Fatigue period, 16 minutes. 





In air of room. 



In testing vessel. 





110 volts. 



480 volts. 



110 volts. 480 volts. 



I 



100 



100 



100 100 



II 



85 



89 



95 93 



Ill 



SO 



83 



91 88 



IV 



75 



79 



88 85 



V 



71 



75 



83 83 



VI 



68 



70 



81 80 



VII 



65 



66 



79 78 



VIII 



62 



60 



77 77 



IX 



59 



58 



76 76 



Again the percentage fatigue was the same whether the 

 gauze was charged (to 100 volts) positively (as of course it 

 must be when a measurement of the photoelectric current is 

 being made) or negatively. This is shown in Table V. 



Table V. 

 Zinc plate in air of room. Fatigue period, 16 minutes 



I 



100 



Gauze positive 



63 



60 



100 



II. to VII... . 

 VIII 



Gauze negative. 

 62 



IX 



60 





i 



It was thought that possibly more effect would be produced 

 by keeping the zinc plate at a high (positive or negative) 

 potential with the rest of the apparatus earthed. The results 

 in Table VI. show no effect of this kind when the potential 

 of the zinc plate is + 100 volts. 



