Electricity through Gases by Charged Ions. 257 



But 



fc=2n&eX , 



since when dX/dx = 0, n 1 =n 2 . 



The measurements of X for gases exposed to Rontgen rays 

 show that unless the current is approaching the maximum value 

 it can attain, X is practically constant for some distance near 

 the middle of the plates; hence in this case we have d 2 X/d% 2 = 

 midway between the plates, and therefore by equations (3) 

 and (5) q=a?i 2 ; substituting this value of n we have 



Swek' 



or 



-X* — =CXo= (6) 



1 



Sirek 



k~ 

 At either plate ^2 = 0, so that JQ-2P 2 — * 2 = 0, thus 



gek 

 -X?_J^ =CX 1 i^ ; .... (7) 



1- 



a 



Sirek 

 hence from (6) and (7) 



.„ Sirek 

 or it 



| i =/5 2 "V (8) 



It follows from this equation that X ly /X is greater than 

 unity, and that the value of this ratio increases from unity to 

 infinity as /3 increases from zero to infinity. We see that /3 

 does not involve either q or i. So that, to take a particular 

 case, when the gas between two plates is exposed to Rontgen 

 rays, the ratio of the electric intensity at the plates to that 

 midway between them is independent of the intensity of the 

 radiation and of the current through the gas. The curves 



