University Studies 



Vol. VII APRIL 1907. No 2 



I. — Fatigue and Recovery of the Photo-Electric Current^ 



BY W. F. HOLMAN 



The experiments of H. A. Wilson- showing that the escape of 

 negative electricity from incandescent platinum disappears when 

 the metal is freed from absorbed hydrogen, and those of Skin- 

 ner,'' that in the glow current through rarefied gases hydrogen 

 atoms serve as carriers of negative electricity from metallic cath- 

 odes to the gas, suggest the possibility of the absorbed gas play- 

 ing a part in the escape of negative electricity from a metal sub- 

 jected to ultra-violent radiations. In fact, the experiments of 

 Wulf* indicate that the presence of absorbed hydrogen increases 

 the photo-electric current from platinum, in that after the plat- 

 inum has been allowed to stand in an atmosphere of hydrogen 

 for some time there is a marked increase of the current over that 

 obtained in air, and again a decrease as the metal supposedly loses 

 its charge of hydrogen. 



This photo-electric current depends on two principal factors, 

 first that arising from the escape of negative carriers from the 



^Read in part before the joint meeting of the American Physical So- 

 ciety and section B of the American Association for the Advancement of 

 Science, Ithaca, June, 1906. 



-Phil. Trans., 202, p. 243. 1903. 

 ^Pkys. Rev., XI, p. 1. 1905. 

 *Ann. d. Physik, 9. p. 946. 1902. 



University Studies, Vol. VII, No. 2, April 1907. 



125 



