292 Trot E. Rutherford on Slow 



expressed by an equation of the form 

 I 



I, 



= l-e~ xt 



where I is the maximum activity. The activity reaches half 



■ ACTIVITY 







r 



F ? 



i 



Cm 



-»» 



>* 



^ o 



o 









>. 







































\ 





C 



: 



t 



> 

 < 











\ 















\ 







 Cm 











j 































r 





3 



its final value in about six days. The value of \ is given by 

 *115 (day)"" 1 . A recovery curve of this character indicates 



