Dr. J. A. Crowther on U J" Radiation. 



12 



absorption of winch in aluminium is 6*1 cm." 



Another 



set of observations, using primary rays with a coefficient of 

 absorption in aluminium of 1*94, gave a value for \' of 6'0. 

 Similar experiments were carried out with radiators of 

 paraffin-wax and of copper. In the case of the Jatter element 



Fig. 2. 



Q-U 



0-Z 



X ^^w 







• 









^ Loo i 









L °3 fj|')\ 







i 





















0-1 



0-2. 



the results were complicated by the presence of a large 

 amount of the fluorescent K radiation of the element, which, 

 in the absence of absorbing screens, produced nearly fifteen 

 times the combined effect of the harder secondary radiations. 

 The K radiation appeared, however, to be almost completely 

 absorbed by the thinnest screen employed (-071 cm. thick), 

 and the results were calculated from the readings obtained 

 with the thicker screens. The results are given in Table IT., 

 \ being the coefficient of absorption of the primary boa in 

 and \' that of the fluorescent radiation excited. 



