Decay of Radio-activity 



575 



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

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

 the emanation, and does not always show the usual simple type of 



40 60 BO 100 



Time in Minutei 

 Fig. 2. 



30 45 60 7 5 



Time in Min>tt,\<. 



Fig. 3. 



