THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE 



[SIXTH SERIES] 



DECEMBER 1921. 



XOVIL The Motion of Electrons in Gases. By J. S. 

 Townsend, M,A., E.E.S., Wykeham Professor of Physics, 

 Oxford, and V. A. Bailey, M.A., Queen's College, 

 Oxford*. 



1. 1 JS T some previous researches published in the Pro- 

 JL ceedings of the Royal Society, a full account has 

 been given of the determination of the motion of electrons in 

 air from measurements of the divergence of a stream moving 

 in a uniform electric field, and the deflexion of the stream 

 by a transverse magnetic force. 



The pressure of the air was varied from about a quarter of 

 a millimetre of mercury to 20 millimetres, and the electric 

 force from about 4 volts to 40 volts per centimetre, which 

 were found to be "the most suitable ranges of the pressure 

 and electric force for observing the motion of free electrons, 

 when the velocity of agitation exceeds the velocity in the 

 direction of the electric force. 



We give in this paper a brief account of the method of 

 rinding the velocities of the electrons and the application of 

 the results to determine some properties of the molecules of 

 gases. The paper also contains results of a large number 

 of experiments which have recently been made on the motion 

 of electrons in hydrogen, nitrogen, and oxygen, with ranges 

 of forces and pressures similar to those used in the experi- 

 ments with air. 



* Communicated by the Authors. 



Phil. Mag. S. 6. Vol. 42. No. 252. Dec. 1921. 3 M 



