650 Mr. J. L. Glasson on the Variation of Ionizing 



Thus when the Faraday cylinder is positively charged the 

 current is given by 



d = ne + nodpe, 



and when the cylinder is negative, 



C! 2 = ne — ncdpe. 

 Thus, 





N). 



It will be convenient to denote this ratio by N ; it is 

 evidently the number of pairs of ions made by a ray in 

 crossing the chamber. 



From the ratio N knowing I and p we can at once 

 determine a or the specific ionization produced by a cathode 

 ray. 



At pressures such as those used here ionization by collision 

 comes in for comparatively low field strengths and there is 

 some difficulty in determining the correct voltage to apply 

 to the gas in order to obtain saturation. One of the curves 



c — c 



connecting--^ — ^ 2 ( = N) with voltage is shown in fig. 2. 



Ffcr. 2. 



1 















*I0 



! 



^•5 













^---' 



























1 



1 

 * 















20 



30 



40 



50 



60 



It will be seen that ionization by collision comes in almost 

 as soon as saturation is obtained. In these experiments a 

 potential of 6 volts was applied to the cylinder. 



Results. 



The method of taking the readings is as follows. The 

 apparatus was exhausted down to a pressure at which the 

 cathode rays begin to be produced. The current through 



