which are produced by Homogeneous Rontgen Radiations. 493 



Now if we take a reading with in position, and another 

 with replaced by G, the silver leaf being uppermost, the differ- 

 ence will represent the ioniaation due to cathode particles on the 

 emergent side of C. The direct ionisation due to Rontgen radiation* 

 will be the same in both cases, since and C absorb the radiation 

 equally. 



If now we reverse C, we can in the same way find the ionisation 

 due to the cathode particles on the incident side of the silver leaf. 

 We must make a correction in the emergent case since the radia- 

 tion passing through the leaf has been absorbed to some extent 

 by the paper and the leaf itself. 



The cathode particles due to soft radiations (Fe, Cu) emerge 

 only from a small fraction of the thickness of the leaf. Hence we 

 may assume that in the emergent case, the radiation has suffered 

 absorption by the whole thickness of the leaf. 



This absorption was found to be 14-8 °/^ for the Fe radiation. 



Hence the emergence values were multiplied by tt^ to bring 



them up to the value which they would have had if the Fe 

 radiation had suffered no absorption. 



_ T- „ . Enerqy of emergent cathode 

 Table I. Ratio = ^ ^ -^ . — r^— ■. 



incident 



Similar corrections were made for the Cu and Se radiations. 

 The corrections for the harder radiations were negligible. The 

 change in the secondary radiation from the leaf when and C were 



