918 Mr. F. P. Slater on .Excitation of 7 Radiation 



Table I. For each heavy element investigated the column 

 headed "Total Ionization" shows the relative ionization, at 

 various absorption thicknesses of aluminium, as read off 

 from the smooth experimental curve. 



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The columns headed "Ionization due to soft rays" and 

 "Ionization due to hard rays" for each element are the 

 analysed components of the smooth experimental curve. 

 There is a discrepancy in each case where the experimental 

 curve bends sharply (see fig. 5), since the experimental curve 

 is very ill-defined at this point. There is no strong in- 

 dication, in the case of the heavy elements, of a radiation 

 intermediate in quality between hard and soft radiations 

 except in the case of Pt, where the soft type is harder than 

 would be expected by comparison with Pb and An. 



