100 



Mr. A. S. Eve on the Radioactive 



used to collect the active deposit from a known volume of 

 air, and the amount was measured by an electroscope. A 

 known weight of pure radium bromide in solution was then 



Table I. 

 Decay of Excited Activity. 



Time 

 in niiraites. 



Radium 

 Emanation. 

 Rutherford. 



Atmospheric 



deposit. 



Eve. 



Difference. 



10 



20 



30 



40 



50 



60 



70 



80 



90 



100 



110 



120 



52 

 45-4 



40-4 

 35-6 

 30-4 

 25-4 



17 : 4 



ii-6 • 



"7 : 6 



52 

 48 

 42-5 

 37-5 

 32-5 

 27-8 

 22-8 

 18-5 

 14'5 

 110 

 8-0 

 66 



+26 

 +2-1 

 4-1-9 

 +2-1 

 +2-4 



+ 1-1 



-"•6 



-l-b 



Fk-. 1. 



£ ^K^ j 



o 



^ 



TTrrte m N/nufes 



taken, and the resulting emanation was collected and trans- 

 ferred to another closed vessel; the excited activity was 

 again obtained on a negatively-charged wire and measured 

 by the same electroscope. In this way the emanation in the 

 air was measured in terms of the amount of radium which 

 would be required to produce it. in all cases the charged 

 wire was exposed for almost three hours, so that practically 



