416 



Dr. Barkla and Mr. Sadler on Secondary 



curve in fig. 5. This was obtained by using the secondary 

 beam from carbon — that is a beam consisting entirely of 



•05 

 04 















Fig. 



o. 





























Zv 



























•03 



CO 

























































\ V 



























A// 



























•02 



Co 



*WvT" 





















































* 





\- v i 























•■01 







S\w 





























X- 





^ 



^ 



^^fe 





_^^_ 



— 





( 



) 



5 5 









7 



5 



l( 



)0 ! 



25 



150 



175 £0 



Atomic Weight of Absorber, 



scattered primary rays — instead of the primary as used by 

 Benoist, and plotting transparency to such a beam as ordinates 

 and atomic weight of absorbing substance as abscissae. 



The following table gives the thickness of each absorbing- 

 plate in centimetres necessary to absorb 75 per cent, of the 

 radiation from each of the substances given in the first column. 

 In the case of the radiation from carbon the numbers are only 

 approximately correct, as they were calculated in the same 

 way as for homogeneous beams. 



Table II. 



Radiator. 



Absorber. 



Zu 



Cu 



Al. 



Fe. 



Cu. Zu. 



Ag. Sn. ! Pt. 



•0386 

 •0309 

 •0254 

 •0214 

 •0173 

 •114 



•0100 



•00929 



•00876 



•0224 



0211 



•0363 



•0241 

 •0338 

 •0203 

 •0170 

 •0137 

 •0242 



•0292 



•0240 



•0195 



0160 



•01265 



•0225 



•00758! -0061 -00839 

 •00625' *OOo08' •nnfiOT 



m 



Co 



Fe 



C 



1 



•00516 -00425 

 •00424' -00350 

 •00362 -00289 

 •0220 -0195 



•00571 

 •00498 

 •00457 

 •0151 



