142 



MR. G. W. C. KAYE ON THE 



anomaly either in the relative intensity of its radiation or in the relative absorption 

 coefficients of different screens in dealing with its radiation. 



The anomalous behaviour of nickel with thin screens appears to be due to the fact that 

 the softer components of its radiation are considerably more penetrating than the softer 

 components of the radiation from iron : possibly also the question of a different distri- 

 bution of the rays comes in. If a similar result is true for the secondary radiations and, 

 judging from the many points of resemblance between the primary and secondary 

 rays from the same metal, such an assumption would not appear to be altogether 

 unwarranted then Messrs. BARKLA and SADLER'S results can be completely explained. 



It is worth noticing that KLKEMAN,* working with very hard incident rays (y rays 

 from radium), found nickel perfectly normal in the intensity of its secondary radiation. 

 liACKETTf measured the quantity of secondary rays produced by the j8 rays from 

 radium, and found that nickel took up a place just below cobalt, and one justified by 

 its accepted atomic weight. DEWAK and JONES} have recently determined the 

 vapour density of nickel carbonyl and confirmed the value 58 '7 obtained by WINKLER 

 (1803) and I'rcTiAiiDS and CusHMAN (1890) for the atomic weight of nickel. 



025 



UNIT ARf* C' iCffLV 



125 



Fig. 10. Al radiator, 20,000 volts. 



Absorptions by Equal Masses of Screens.- The interesting feature in the curves of 

 figs. 7, 8, and is the homogeneity manifested when radiator and screen are alike. 

 Let us examine in turn the way in which the radiations from the metals aluminium, 

 copper, and platinum are dealt with by screens of equal masses. In figs. 10, 11, 

 and 12, Iog 10 (I/I ) is plotted against the mass per unit area of each of the screens. 



* KLKEMAN, 'Phil. Mag.,' p. 618, Nov., 1907. 

 t HACKETT, 'Nature,' 75, p. 535, April, 1907. 

 J DEWAR and JONES, ' Proc. Roy. Soc.,' A, 80, p. 234 (1908). 



