410 



Prof. C. G. Barkla on the Spectra of 



understanding of these phenomena to be acquainted with the 

 penetrating powers of these fluorescent radiations. 



Fisr. 3. 



440 



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60 



80 100 l£0 140 160 



/itomic Weight of /fao/Ar/HZ £l£me.nt 



200 £10 



It has been shown that eafch element has its own charac- 

 teristic fluorescent line spectrum in X-rays. This is very 

 conveniently represented as is a spectrum of ordinary light, 

 except that without a knowledge of the wave-length we are 



