750 



Dr. C. G. Barkla and Mr. C. A. Sadler on 



Fe, Ni, Cu, and Zn are among the elements from which a 

 homogeneous characteristic radiation is emitted in consider- 

 able intensity when the primary beam is of ordinary pene- 

 trating power. Ag emits a homogeneous radiation when 



Fm. 3. 



Absorption //v M (2l\ 



subject to a primary more penetrating than this radiation,, 

 that is more penetrating than any radiation here used. Sn 

 emits a radiation which on the whole appears slightly more 

 absorbable than the silver radiation, but although it has not 

 been investigated minutely, there is strong reason to believe 

 this consists of two homogeneous radiations, a very soft one, 

 and one either just more absorbable or just more penetrating 

 than that characteristic of Ag. 



Pt and Au have been found to emit a radiation which, 



