748 Mr. & Mrs. Soddy and Mr. A. S. Kussell on the 



E>F>G if thickness be only 0-3 cm. From VIII. o£ 

 Table IV. it may be seen that if brass is used as absorbent 

 instead of lead the variation of the other factors of the 

 disposition have no effect on the value of the leak. 



Table IV. 





Disposition. 



Nature of the Effects. 



I 



1 lead (7*5 cm. thick), 



2 wood (3 cm. thick), 



3 absent, 5 wood. 



Leak greater without 4 (lead) than 

 with it. — (A and B.) 



II 



1 lead, 2 wood, 4 absent, 

 5 wood. 



Leak greater without 3 (lead) than with 

 it.— (C and D.) 



Ill 



1 lead, 2 wood, 3 lead, 

 5 wood. 



Leak greater without 4 (lead) than with 

 it.— (E and F.) 



IV 



1 lead, 2 wood, 5 lead. 



Leak the same whether either or 

 both 4 and 5 (lead) be present or 

 absent. — (G.) 



V 



1 lead, 2 lead. 



Leak the same whatever be the nature 

 of 3, 4, or 5, and whether 3 or 4 be 

 present or not. — (H.) 



VI 



1 lead, 2 wood, 3 brass, 

 5 brass. 



Leak practically the same whether 

 4 (lead) be present or not. — (J.) 



VII. ... 



1 lead, 2 wood, 5 lead. 



Leak the same without 4 (brass) as with 

 it and greater than when 4 (lead) is 

 preseDt. — (K.) 



VIII.... 



1 brass, 2 wood, 3 brass 

 or lead, 5 wood, brass, 

 or lead. 



Leak the same whether 4 (lead) is 

 present or not. — (L.) 



IX 



Thick lead electroscope 

 whatever be the nature 

 of 1, 2, 3, or 5. 



Leak the same whether 4 (lead) is 

 present or not. 



From these observations the following results have been 

 deduced. The process of absorption of the y-rays by lead 

 causes a secondary radiation, probably an incidence radiation, 

 to be produced by the primary in the metal. This radiation 

 is absorbed by the lead also and so cannot emerge from the 

 lead in appreciable amount. In the experiments described 

 in Table IV. the radium is inserted between thicknesses of 

 lead and of wood. Through the wood this peculiar radiation 

 escapes, and when it has escaped it can penetrate with ease 



