﻿516 



Dr. J. Robinson on tlte Photoelectric 



This seems to show that occluded gas in the film influences 

 the actual magnitudes of the velocities, though not the ratio 

 for the incident to emergent effects. The values given 

 for the velocities represent steady values which are only 

 obtained some time after the film was deposited. Imme- 

 diately after a film has been deposited the velocities vary 

 considerably, but more for incident than for emergent light. 

 A constant ratio was only obtained sometime after depositing. 

 Frequent attempts were made to find whether it was possible 

 to eliminate these initial variations by passing the current 

 for a long time before depositing the film, so as to get rid of 

 occluded gas from the platinum electrode, but so far it has 

 not been found possible to do this. 



Fig". 3. — Film of 5 minutes. 



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 30 





















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Fi^. 4. — Film of 8 minutes. 



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PoTEIVTIfiL DIFFERENCE 



The results of Table II. are shown graphically in figs. 3-6. 

 It is seen that in every case the photoelectric current 



