Section III., 1908. 



[S] 



Trans. R. S. C. 



II. — The Secondary y Rays Due to the y Rays of Radium C. 



By A. S. Eve, D.Sc, Associate Professor of Mathematics and 

 Lecturer in Radioactivity, McGill University, Montreal, 



(Communicated by Dr. H. T. Barnes, and read May 26, 1908.) 



The Rontgen rays and the y rays from radioactive substances 

 have so many properties in common that they are generally believed 

 to be fundamentally of the same nature. But the secondary radia- 

 tions caused by X rays and by y rays, respectively, appear at first to 

 be widely different. Whilst the y rays give rise to secondary radia- 

 tions following the order of the densities of the radiators, the X rays 

 cause secondary radiations strongly diverging from that order. Thus 

 Townsend found actually more secondary radiation from solid paraffin 

 than from lead. The values he obtained were: — 



TABLE I. ' 

 X Rays, Secondary Radiation. 



Proc. Camb., Phil. Soc. X, p. 217, 1899. 



Let us compare the secondary radiations from the ;;/ 

 radium bromide enclosed in lead. 



TABLE II. 



7 Rays, Secondary Radiations. 



Radiators. 



Lead . 100 



Copper 61 



ravs of 



Brass 59 



Aluminium 30 



Glass 35 



Solid Paraffin 20 



Phil. Mag., Dec, 1904. 



In this case the order of secondary radiation is that of density. 



