Dr Barkla, Phenomena of X-Ray Transmission. 263 



Au because in these the radiation A is not excited. When, 

 however, the primary radiation is sufficiently penetrating to 

 excite the radiation B in Fe, Ni, Cn, Zn, these take their proper 

 place. A radiation sufficiently penetrating to excite radiation 

 B in Ag, Sn, Pt, Au was not used, but when the radiation was 



800 

 600 

 400 

 200 



200 



n 



750 



^ICL 







100 



50 



M 



25- 



_ Au 



'^/V''*' l/erT/ 'soft' Radiation 



Sn/ 





v.-' 



if 



^ -^ Rather 'soft Radiation 



^^y^,^^^^^ Fairly penetrating Radiation 



50 100 150 200 



Atomic Weight of Absorbing Substance 



Fig. 3. 

 Note : Letters X , A and B denote the characteristic secondary radiations 

 excited (see fig. 1). 



sufficiently penetrating to excite the radiation A in Pt and Au, 

 these took their proper places with respect to Ag and Sn. 



Thus in fig. 3, curves I, II and III exhibit the relation 

 between the absorption in different elements and the atomic 

 weight of the absorbing element for three different radiations. 

 Curve I was obtained by using the very soft homogeneous radiation 



VOL. XV. PT. III. 18 



