Decay of Radio-activity 



bib 



radium or thorium become coated with a radio-active deposit. The 

 rate of decay of tliis activity depends on the time of exposure to 

 the emanation, and does not always show the usual simple ty^ie of 



40 r 



so'f 



Decay of 

 of Radiun. 



Excite 

 ^ short 



Activuy 

 exposure 



eo ao 

 Time in Minutes 



Fig. 2. 



120 UQ 



100 



46 60 76 



Time in Minutes. 



\ia 



FiR. 3. 



