of Rontgen Rays in Transmission through Matter. GG5 



This explanation of the phenomena is borne out by the 

 following experiments. 



Fig-. 2. 



An electroscope E 3 (fig. 2) was placed with its aperture 

 parallel to the primary beam. A guide S' was arranged so 

 that different substances could be placed in the path of the 

 beam entering E 2 . The secondary radiations excited in these 

 could be measured by E 3 . The ionization in electroscope Ej 

 serving as a standard. 



Strips of Ti, Cr, Fe, Cu, Zn were used as radiators. The 

 amounts by which the ionization in E 3 was diminished when 

 sheets of iron and aluminium respectively (absorbing the 

 same percentage of the primary) were put at S, were noted. 

 These diminutions in the secondary radiation indicated which 

 constituents of the primary were cut off by the iron and 

 aluminium respectively. The results are tabulated below. 



Table VII. 



Secondary 

 Eadiator. 



X/p for 



secondary 



radiation 



in Al. 



Per cent, by 

 which Al in pri- 

 mary (cutting off 

 63 per cent.) cuts 

 down secondary 

 radiation. 



Per cent, by 

 which Fo in pri- 

 mary (cutting off 

 62 8 per cent.) cuts 

 down secondary 

 radiation. 



X/p for 

 secondary 

 radiation 



in Iron. 



Ti 



230 

 136 



88 5 

 47-7 

 39-4 



681 

 63-7 

 53-5 

 45-3 

 423 



54 2 

 62 

 69-6 

 55 



-162 



173 

 104 

 66-2 

 268 

 221 



Cr 



Fe 



Cu 



Zn ......... 



Phil. Mag. S. (>. Vol. 21. No. 125. Man 191 1. 2 X 



