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LIII, On Conditions controlling the Drop of Potential at the 

 Electrodes in Vacuum-tube Discharge. — (Second Paper*). 

 By Clarence A. Skikner, Adjunct Professor of Physics, 

 University of Nebraska-^. 



THE results of experiments described in a former com- 

 munication seem to indicate that the drop of potential 

 at the electrodes in vacuum-tube discharge is caused by a 

 resistance to discharge of the gas ion to the metal electrode, 

 this resistance increasing with the velocity with which the 

 ion impinges on the electrode. To explain this it is con- 

 ceived that the discharging ion must give up its kinetic 

 energy with — or before it can give up — its charge. Different 

 physicists have suggested that at least a momentary chemical 

 combination takes place between the carrier and the electrode. 

 It is very plausible then that the elastic reaction of the ion 

 impinging on the electrode introduces a force resisting dis- 

 charge, the resistance increasing with the velocity of impact. 

 This being true, the ions approaching the electrode will 

 accumulate at its surface until the thereby increased electric 

 intensity becomes sufficient to cause as many to discharge 

 in a given interval as arrive at the electrode during the 

 same interval. From this standpoint the drop of potential 

 will depend on the time required for the discharging ions, 

 arriving with a definite velocity, to come to rest at the 

 electrode — their kinetic energy being first given up by 

 collision with both the neighbouring gas molecules and the 

 electrode. 



This being a mechanical explanation of the phenomena the 

 laws of mechanics should be applicable in deducing and in 

 predicting experimental results. The complicated nature of 

 the problem, however, presents at present a discouraging 

 barrier to any rigid mathematical discussion, but a simplified 

 case may be considered in order to test the applicability of 

 the view. 



Suppose perpendicular to the plane of the figure (fig. 1) a 

 plane electrode OA. Moving freely in the direction «0 per- 

 pendicular to the electrode is a particle of mass m carrying a 

 positive charge e. This particle is supposed to be driven 

 towards the electrode by a uniform field equal to 



aO ~~ s ' 



* The first paper under this title was published in the Phil. Mag. of 

 Dec. 1901. 



t Communicated by the Author, having been read before the American 

 Association for the Advancement of Science, June 1902. 



