Radioactivity of Lead ami other Metals. 775 



drop in the conductivity occurred to between 8 and 8*5 

 divisions per minute. 



If the air was again left undisturbed in the cylinder, its 

 conductivity rose once more and finally reached the maximum 

 value of approximately 11 divisions per minute. In con- 

 ducting these operations it was not found necessary to draw 

 fresh air through the cylinder for more than twenty minutes 

 in order to lower the conductivity to the minimum value. 



Table VII. 



Cylinder No. 1. 



Conductivity 

 Date. (Arbitrary Scale). 



May 16 7-7 



17 9-0 



18 9-6 



19 10-32 



21 10-65 



22 11-09 



24 11-02 



Fresh air blown through cylinder for 

 twenty minutes : 

 May 24 8\54 



25 8-91 



27 9-83 



29 10-16 



June 1 10-79 



4 11-3 



Fresh air again blown through cylinder for 

 twenty minutes : 



June 4 8*1 



Fig. 1. 



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 10 



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IS 17 '13 19 20 21 22 23 24 25 26 27 28 29 30 32 1 2 3 4 5 



MAT JUJVE 



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