382 Mr. P. W. Burbidge on the Absorption of the 



a lead tube allowed the silver rays to pass out to the absorp- 

 tion chamber (fig. 2). Direct radiation from the bulb fell 

 on the silver plate only, and scattered radiation from 

 surrounding walls was reduced to a minimum. 



Fig. 1. — Absorption-Curve of X-Rays. 



8-0. 



1-5 



T 



Log lo I 



10 

















I 





















\V 











s 



1 



























»V N 







! 











"£\ \ 





1 



i 

 1 





\^ 



•rv 



■JU— 







s. 



i 









<^ 



e*v 









o-i 



•3 -4 -5 



Cms. ofAl 



Absorption curves of the rays were determined by placing 

 sheets of aluminium betweem the absorption chamber and 

 the large lead box. The curve for the rays used (fig. 1) 

 showed considerable homogeneity to exist. The radiation 

 appeared homogeneous till 95 per cent, was absorbed, the 

 effective coefficient of absorption in aluminium, fi M , being 

 6*01. Assuming the mean for silver K rays in aluminium 

 to be &6 (corresponding to Barkla's figure 2*5 for p/p, the 

 mass absorption coefficient), the curve can be analysed into 

 two straight lines corresponding to radiations with yu,= 6*6 



