Secondary Radiation. 235 



of the radium and the ionization measured at each stage. We 

 thus get from one experiment, the intensity of the primary 

 rays after they have passed through various thicknesses of 

 foil: and from the other experiment we get a measure of the 

 secondary rays produced by the primary after passing through 

 the same thickness of foil as before. 



The results are as follows, the primary and secondary 

 radiation being expressed so as to have a maximum of 100 

 in each case. 







Secondary 



Sheets of foil. 



Primary Radiation. 



Radiation. 







100 



100 



1 



61 



56 



2 



4:7-5 



41 



4 



40 



31 



8 



33 



19 



16 



27*5 



10 



32 



23 



7 



























Fig 



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The curves in fig \\ are plotted from the above numbers. 

 The curves show at a glance the relative efficiency of the 



