Decay of the Active Deposit from Radium. 405 



Bronson *, and has been attributed to the slowly moving 

 ft rays emitted by radium B, recently discovered by (Schmidt |. 

 Since these rays are emitted by radium B. whereas the a 

 and the more penetrating rays are emitted by radium C, it is 

 to be expected that the rate o£ decay as measured by these 

 two types of radiation will be different. 



Although this explanation seemed probable, it was thought 

 to be of interest to test this point somewhat more carefully, 

 to make sure that this explanation is really the correct one. 



Fie:. 1. 



The following experiments show conclusively that this is 

 the case. 



As the whole effect to be measured was very small, it was 

 necessary to make somewhat careful experiments to test the 

 matter, and the method used was as follows. 



Two ionization-vessels A and B (fig. 1) were connected to 



* Bronson, Phil. Mag. July 1906. 



t Schmidt, Phys. Zeit. vi. p. 897 (1905). 



