118 



THE ROYAL SOCIETY OF CANADA 



7 

 6 



I 





0/5 



0-3 O'^S 



MASS or AB50f?B£ff IN GMS/CAr.^ 



Fig. 4 



slower ones. Intensities of this order are much smaller than the 

 natural leak and consequently a slight fluctuation of leak will give a 

 very large eiror in the apparent intensity. 



For these reasons it seems almost certain that with a very intense 

 source of radiation and a more precise method of measurement a 

 measurable quantity of scattered radiation would be detected through 

 a mass of absorber more closely approaching the range of the primary 

 rays. 



(2) Scattering is not a surface phenomenon (see Fig. 5) . Some of 

 the jS-particles will have penetrated a considerable distance into the 



radiating material before being deflected back, 

 and some will undergo several deflections inside 

 the radiator before emerging backwards. Hence 

 there will be an average distance inside the 

 radiator which the scattered particles traverse, 

 and while doing so they will lose velocity just 

 as has been shown to be the case whenever 

 /3-rays pass through matter. It is evident, 

 then, that the real range of the scattered rays 

 is the range actually found plus the equivalent 

 FJg- ^ of the average path in the radiator. It is not 



impossible, though it cannot yet be stated definitely, that this 



