414 Dr. Barkla and Mr. Sadler on Secondary 



substances were experimented upon in the inverse order were 

 61-2, 61-6, 61-5, 61-3, 61-3. 



Fig. 3. 



6000 



5000 



4000 



X 



3000 



-see- 



-&m 



200Q 



1000 



-4QQ- 



-aee 



55 -60 65 



Atomic IA/£icht of fffiOiATOR 



55 



65 



The curves obtained from the experiments on iron and 

 copper were too irregular to admit the determination of 

 accurate results. These are consequently omitted. 



The striking irregularities in form shown by the curves 

 obtained from experiments in which iron and copper were 

 used as the absorbing substances were obviously due in one 

 case to the absorption by iron of the rays from iron and 

 cobalt being much lower than might have been expected from 

 observation of the general relation between atomic weight 

 of radiator and absorbability of the emitted radiation and 

 the absorption by copper of the radiation from copper 

 being low. 



