tJie Corpuscular Hypothesis of the y and X Rays. 407 



due to an agent which does not change when the gas is 

 changed, viz. the /3 rays from the vessel walls. The relative 

 ionizations in different gnses due to the y rays must be the 

 same as the relative ionizations due to fi rays ; and this is 



Fig. 3. 



GrLF, 



found to be the case very exactly, unless there is such a mass 

 of gas in the chamber that the second source of ft rays becomes 

 important. This occurs when the gas contains heavy atoms 

 like those of iodine. The " atomic ionizations " by /3 and 

 by y rays are set out below and show the close parallelism. 

 They are taken from a paper by Kleeman *. 



(3 



H. 



0. 



N. 



O. 



S. 



CI. 



Br. 



I. 



018. 

 018 



046 

 0-46- 



0-475 

 0-45 



058 

 0-58 



1-60 

 1-60 



1-44 

 1-44 



2-67 

 2-81 



410 



4-50 







If any part of the ionization in the gas were due to a direct 

 action of the y rays, and we were to reject the simple expla- 

 nation just given, we should certainly find it extraordinarily 

 difficult to explain the almost exact similarity of these two 

 rows of figures. This would be the case on the entity hypo- 

 thesis : if the y rays were supposed to be spreading pulses, 



* Proc. Roy. Soc. lxxix. p. 220, Feb. 1907. 



