Manchester Monoirs, Vol. liv. (1910), No. 8. 



/CO- 



/O xo 30 W ^O 60 



Fig. I. 



The question at once occurs in what proportions do 

 Radium A and Radium B exist on the disc? 



Consider the supply of Radium B to the disc due to 

 the disintegration of Radium A. 



If ;/ = number of particles of Radium A at the bottom 

 of the tube, then 



..Q, = ^n{v - ) 



