Manchester Memoirs, Vol. liv. (1910), No. 8. ii 



The variation in the alpha ray activity due to the 

 Radium B radiated to the disc has been calculated from 

 the expression Rt\- R\ where 



K,=—!i(i—ae - +ve - )e ^ 



and R'^ . \ Q,{e ^^'^-e" ^-^ ''' 



) where (9, = J;/(i -e"^''^). 



These numbers will be found in Column 3, and the 

 result of adding Columns 2 and 3 is reproduced as the 

 full line curve in Fig: 3. 



1^ 



>-^ 



JO 



fO 20 <30 UO JO 60 



7/lcozLofeJ . 



^ig' 3- 



It^will be seen that the experimental points, indicated 

 by small circles, do not lie exactly on the curve. 



Following the same procedure as for the short expo- 

 sure, and assuming that twice as much Radium B is 

 radiated up the tube as Radium A, we obtain the dotted 

 curve in Fig. 3. 



