THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 





[SIXTH SERIES.] 



MARCH 1910. 



XXXV. Homogeneous Corpuscular Radiation. By Charles 

 A. Sadler, M.Sc, Oliver Lodge Fellow, University of 

 Liverpool*. 



[Plate V.] 



DURING investigations upon the nature of Rontgen rays 

 various experimenters observed that when these rays 

 were allowed to fall upon metal plates secondary radiations 

 were emitted. From an element of low atomic weight this 

 radiation was of a type indistinguishable from the exciting 

 beam ; it carried no charge and had the same penetrating 

 power as the primary. From an element of higher atomic 

 weight a radiation carrying no charge, but considerably less 

 penetrating than the primary beam, was produced!. But in 

 addition to the secondary radiation of these types there was 

 found to exist in some cases a radiation which was completely 

 absorbed in a few millimetres of airf. This radiation was 

 found to consist of negatively charged particles identical in 

 character with the negative corpuscles which carry the 

 current in a discharge-tube. 



It was soon found § that the intensity of this corpuscular 

 radiation depended both upon the " hardness " of the primary 

 beam employed and upon the nature of the metal plate upon 

 which it fell, but the results obtained by different investi- 



* Communicated by the Author. 

 | Barkla, Phil. Mag. June 1906, pp. 812-828. 

 % Townsend, Proc. Camb. Phil. Soc. x. p. 217 (1899). 

 § See publications by Perrin, Sagnac, Langevin and Townsend, and 

 others on corpuscular radiation excited by X rays. 



Phil Mag. S. 6. Vol. 19. No. 111. March 1910. Z 



