114 



Dr. W. Makower and Dr. S. Russ on the 



law of absorption of radium C by air. The results are given in 

 Table I. (p. 113) and fig. 6. The absorption at different 

 pressures can be seen frouiUhe last column, which gives the 

 quantity of radium C reaching the disk, the mean of the two 

 vacuum readings being taken as 100. 



Absorption of RaC by Air. 



O Of -CZ 03 04 -OS 06 0] 08 



Although the results are not very consistent, the order of 

 magnitude of the absorption can be seen from the numbers 

 given. By a comparison with the absorption of the radiant 

 matter from the emanation condensed at the bottom of a tube 

 in liquid air, studied in a previous paper, it will be seen that 

 radium A and radium B, when expelled as the result of a 

 recoil from an a particle, can penetrate only about 40 times 

 as much air without being stopped as radium C when it 

 recoils as the result of the emission of a ft particle from 

 radium Bx Now it has already been calculated that the 

 energy possessed by radium C should be less than one- 

 millionth of that possessed by radium A or radium B after 

 recoil. The order of magnitude of the absorption of radium C 

 is therefore far smaller than was to be anticipated. It is 

 difficult to explain this discrepancy ; if an a particle of slow 

 velocity were expelled during the transformation of radium B 



