2S6 



Cool'sey — Corpuscular Rays produced in 



that the velocity does not depend at all on the intensity, but 

 does depend on the penetrating power of the primary Rontgen 

 rays producing them ; the harder or more penetrating primary 

 rays producing higher velocities in the corpuscular rays. From 

 some results published by Prof Bumstead* on the heating 

 effects produced when Rontgen rays are absorbed by different 

 metals, I was led to investigate this last type of rays, which 



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we shall refer to as "Corpuscular Secondary Rays." with a view 

 to determining the relative number produced in different 

 metals for equal absorptions of the same beam of Rontgen 

 rays. 



Apparatus. 



It was decided to investigate these corpuscular secondary 

 rays by means of the ionization which they produce, but owing 

 to the great ease with which they are absorbed it was found 

 that the thinnest aluminium which could be obtained would 

 stop all but a few of these rays. It was necessary, therefore, to 

 *This Journal, xxi, Jan., 1906. 



