﻿Motion of Electrons in Argon and in Hydrogen. 1035 



very small when the electric force is small ami the plate P 

 is at the potential 6V. The current is increased by 

 increasing the pontential of the plate P, and with the gauze 

 at the potential 3V the electrons pass through a, distance of 

 one centimetre under the force Z before reaching the slit. 

 With the gases at the higher pressures the number of 

 collisions of each electron with molecules of the gas in this 

 distance is very large, and the motion of the electron acquires 

 ;the steady state corresponding to the force Z before passing- 

 through the slit. 



6V 



Fig.l 

 P 



3V 



zv C 



R a 



R, 



n 



R, 



In the instrument with the slit 4 centimetres from the 

 receiving electrodes there are three guard-rings between 'R x 

 and the ring A with the slit, as shown in the diagram, 

 page 875, Phil. Mag. Dec. 1921. The dimensions of the 

 electrodes and the guard-rings were the same in both 

 instruments. 



In order to avoid errors which might arise from contact 

 potentials at the surfaces of the rings R or the electrodes E, 

 the metal surfaces were all electroplated with silver which 

 is less liable to become oxidized than brass. The variations 

 in contact potential which may arise owing to oxidation 



3X2 



