PEOCEEDINGS 



OF THE 



dtamkitrge ^Ijil0S0p]^kaI Snmtg* 



So7ne fatigue effects of the cathode in a discharge tube. By 

 R. Whiddington, B.A., Hutchinson Research Student of St John's 

 College. (Communicated by Professor Sir J. J. Thomson.) 



[Read 17 May 1909.] 



Skinner's* experiments on the vacuum tube discharge seem to 

 suggest that charged hydrogen atoms emitted from the cathode 

 play a considerable part in the carriage of the current. 



Chrisler-f- has studied experimentally the effect of absorbed 

 gases on the photoelectric activity of metals, coming to the 

 conclusion that hydrogen again plays a large part in the photo- 

 electric current. 



The pi'esent note describes the results of some simple experi- 

 ments designed to show what influence the gases occluded in the 

 cathode have on the emitted cathode rays. 



The method employed is qualitative and hardly capable of 

 quantitative application. It consists of comparing the behaviour 

 of a cathode, previously treated in various ways, with an exactly 

 similar, and similarly situated untreated standard electrode, in 

 the same tube. By this means the complicating influence of 

 pressure changes was eliminated, for the change over from one 

 cathode to the other was instantaneous leaving no time for a 

 change in pressure. 



If the looked-for effect has any existence it is reasonable to 

 suppose that it might be greatest in the case of a charcoal 

 cathode. For carbon can be made to absorb vast volumes of 

 many gases. 



* Fhys. Rev. Vol. xxi. 1905. 

 t Phys. Rev. Vol. xxvn. 1908. 



VOL. XV. PT. III. 13 



