596 Prof. J. S. Townsend and Mr. V. A. Bailey on 



It will be seen that no great difference between the three 

 gases is to be found from the measurements of the velocity W 

 in the direction of the electric force alone. 



Fig. 1. 



12 



10 



8 



WxlO 



.5 













yT 













&S 















3$ 





%2& 































^ 



z s/ 

















































z 

 p 





0-5 



10 



The values of k for the pure argon, for nitrogen, and for 

 hydrogen in terms of the ratio Z/p are given by the curves 

 in fig. 2, which show a great difference between the three 

 gases. 



5. The velocity of agitation u of an electron, its mean free 

 path /, and the proportion X of the energy of an electron 

 lost in a collision with a molecule of argon, are given in 

 Table I. The numbers for W, I, and \ are obtained from 

 the formulae 



u =1-I5xl0 7 x s/k, 

 p m u 



\ =2-4,6 x 



W : 



the numerical factor in the last formula being an approxi- 

 mate estimate as explained in the previous paper *. 



* Pbil. Mag-. Dec. 1921, p. 889. 



