MancJicster Memoirs, Vol. liv. (1910), No. 8. 9 



on this curve. Bearing in mind the possibility that 

 Radium A and Radium B may not be radiated up the 

 tube in equal quantities, the limits of any such an equality 

 can be found by varying the proportion in which the 

 quantities (i) and (2) are added together. 



The dotted line in Fig. 2 shows the decay curve that 

 would be obtained if twice as much Radium B had been 

 projected as Radium A. Inspection shows that the 

 experimental points lie within the limits defined by the 

 two curves drawn. 



Hence from the analysis corresponding to an exposure 

 of 10 minutes, it may be pretty confidently stated that 

 Radium A and Radium B are projected up the tube in 

 nearly equal proportions. 



The case of an exposure lasting three hours admits of 

 comparatively simple treatment, for in this case Ruther- 

 ford has shown that a state of equilibrium exists between 

 the different short lived products obtained from the 

 Emanation. 



Hence, owing to the direct firing of Radium A, we 

 have at the moment of removal the same number of 

 Radium C particles breaking up per second as Radium A 

 particles. If Radium B is radiated up the tube in an 

 equal proportion to Radium A. then a similar number of 

 Radium C particles will be breaking up per second on 

 the disc at the instant of removal due to this cause as 

 when the radiation is due to Radium A. 



Hence the initial alpha ray activity due to the first 

 cause will be twice that due to the second. 



The variation in the alpha ray activity of the disc due 

 to the Radium A radiated on to it corresponds to the well 

 known decay curve for an exposure of three hours. This 

 variation is tabulated in Table II., Column 2. 



