THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



A PEIL 1910. 



XLIX. On the Pressure of the Electric Wind in Hydrogen 

 containing traces of Oxygen. By A. P. Chattock, Pro- 

 fessor of Physics, and A. M. Tyndall, B.Sc, Lecturer in 

 Physics, in the University of Bristol*. 



IN a recent paper t dealing with the influence of oxygen 

 on point-discharge in hydrogen at atmospheric pressure 

 the present authors showed that if the amount of oxygen 

 in the hydrogen be reduced to a fraction of one per cent., 

 certain phenomena accompanying the negative discharge are 

 modified in a marked way. 



Among these it seemed possible that the velocity of the 

 negative ions was to be classed, its value being apparently 

 raised as the hydrogen approached a state of purity (loc. cit. 

 pp. 44-47). As, however, the principle upon which this 

 statement was based is not above criticism (see below p. 45b') 

 it seemed desirable to measure the ionic velocities again in 

 some other way. 



This we have now done, using the wind-pressure method + 

 for the purpose, and the results obtained are discussed in 

 what follows. 



* Communicated by the Authors. 

 t Phil. Mag. 1908 [01 vol. xvi. p. 24. 

 % Phil. Mag. 1899 [5] vol. xlviii. p. 401. 



Phil. Mag. S. 6. Vol. 19. No. 112. April 1910. 2 G 



