Radio activity of Lead and other Metals. Ill 



conductivity, but the initial value of 54*5 divisions was never 

 reached without re-cleaning and washing the inner surface 

 of the lead. 



Ffc. 2. 



b ^ 63 



^ ^ 60 



5 7 9 M 13 15 17 49 2/1 23 25 27 29 



JUNE 



From these observations it would appear that the rise in 

 the conductivity of the air in both cylinders may be divided 

 into two parts and ascribed to different causes; the one being 

 associated with some change in the surface of the metals 

 used in the construction of the cylinders, and the other with 

 some substance which becomes diffused throughout the air, 

 and can be blown out with it* 



With cylinder No. 1 the part due to the first cause was 

 very small, and in no case exceeded 10 or 12 per cent, of the 

 minimum reading obtained for the conductivity. 



The second part, too, was very definite with this cylinder, 

 and when the maximum conductivity had been reached it 

 corresponded to a reading of between 2*5 and 3 divisions 

 per minute. 



With cylinder No. 2 both parts of the rise in conductivity 

 were well marked. But as the numbers in Table VIII. show, 

 both parts exhibited a steady increase during the time the 



