300 Cooksey — Corpuscular Rays produced in 



57 per cent for an increase of velocity of about T8 per cent. 

 Considering the slight variation in velocity with which the 

 corpuscles come off from the different metals in our experi- 

 ments, as shown by the variation in absorption, it seems safe 

 to assume that the specific ionization due to the corpuscles 

 from the different metals under consideration is approximately 

 the same for all the metals. 



To find the relation between N' and the ionization measured 

 let n be the number of ions produced by one corpuscle per cm. 

 of path, and let K be the coefficient of absorption in air for the 

 corpuscles from any metal. Then the number of ions pro- 

 duced in a layer of air between x and x+dx is n~N'e-&xd%, 

 and the total number of ions produced is 



ff-Kx nN' 

 )iN' I e dx=-jf- 



This is proportional to the quantity measured, say Q. There- 

 fore 



n 



In comparing the number of corpuscles produced in any 

 metal with the number produced in lead, we have: 



The ratio of the number of corpuscles produced in any metal 

 to the number produced in lead for equal absorptions and equal 

 intensities of the primary rays is equal to 



XK Q N 



The coefficient of absorption for the corpuscular rays in pass- 

 ing through any substance is proportional to the density of the 

 substance. We bave found the absorption of the corpuscular 

 rays in aluminium; let the coefficient of this be called k. Let 

 p be the density of any substance, and p' the density of alumin- 

 ium; then the above reduces to 



N A z ¥ p Q 



N, A k\ Pl Qi 



The values of \ were measured for the different metals used. 

 The values of h for the different metals are proportional to 

 the slopes of the straight lines plotted with the curves in the 

 cases where the lines pass through the origin. In the case of 

 the secondary rays produced by the soft primary rays, where 

 the straight lines do not pass through the origin, the following 

 method for finding k was used. The slope of the straight line 



