545 
Secondary Cathode Rays from gases. 
between them) is 3 - 7 x 10 8 cm. /sec. : the difference between these 
values is hardly greater than the errors of experiments. 
The constancy of the velocity of the corpuscles would be 
attained if the primary rays were to detach in the first instance 
from the molecules of the gas, not a corpuscle, but a more complex 
system, say for example a doublet containing a corpuscle and 
a positively charged particle, the two constituents of the doublet 
rotating rapidly round each other. If this doublet were subse- 
quently to be broken up, the corpuscle flying off with the velocity 
due to its rotation in the doublet, and if similar doublets came 
from the molecules of different gases, the velocity of the secondary 
cathode rays would be independent of the nature of the gas as 
well as of the intensity of the rays. 
I wish to acknowledge the great help I have received from 
Mr G. W. C. Kaye, of Trinity College, in carrying out this investi- 
gation. 
