Fatigue and Recovery of the Photo-Elcctric Current y 



being" affected in different degrees. The probable explanation is, 

 that use as anode or even contact with the gas (possibly not en- 

 tirely pure) tarnished the surface of the metal, and this reduced, 

 as is known, the photo-electric action. By use as cathode with 

 the glow discharge the metal surface in these tests was probably 

 cleaned of tarnish but not sufficiently depleted of its negative car- 

 riers to reduce the photo-electric current. 



It was thought possible to obtain less complicated results by 

 operating with the glow discharge in argon instead of hydrogen, 

 since, according to Skinner, use as cathode in this gas serves to 

 deplete the store of hydrogen, while use as anode has nO appre- 

 ciable effect. The results obtained are recorded in table VI. For 

 these experiments, the capacity, C. v.^as again reduced to 1,400 

 cm. 



Table VI 



The results here are very similar to those recorded in table V, 

 with the exception that the use of qopper and silver as anode 

 with a glow current in argon appears to clean the metal of its 

 tarnish, in that it increases its photo-electric current. It should 

 be remarked that in no case did a I'isible tarnish appear when 

 argon was used. ■ 



Although the results given in tables I-IV could not be dupli- 

 cated, they are so definite that it seems probable that the desired 

 state of depletion of the metal by use as cathode was not reached 

 in the later experiments. Unfortunately further prosecution of 

 the investigation was impossible. 



133 



