by a Particles from Radium Emanation. 



911 



absorbing material in millimetres. It will be seen that the 

 points marked in open circles lie very nearly on a straight 

 line which corresponds to a radiation having an absorption 



Fio-. 3. 



20 



Loo 



/on/Sd 



1-6 



1-2 



0-8 



0-4 



f/i?/7 X© ^v 



°/ 









i — — ~ 



i 

 1 





Vv 



\^0 































\ 





'\ 













\ 



X 



/vr/rtx. of Lead 



coefficient 1*8 cm. -1 in lead. The radiation is apparently 

 homogeneous with almost an exponential absorption, though 

 there was some experimental evidence of a softer radiation 

 present. 



Tin. The absorption in lead of the tin radiation is shown 

 by curve T T in the same figure. Again the points 

 marked by filled-in circles lie almost on a straight line, 

 corresponding to a homogeneous radiation of absorption 

 coefficient 2'1 cm. -1 in lead. Here also there was some 

 experimental evidence of a softer radiation. 



Owing to the effect of the primary /8-rays of radium B 

 and the high-speed /3-rays of radium C, it was impossible 

 to reduce the thickness of the absorbing lead base much 

 below 2 mm., and consequently the existence and nature 

 of this softer radiation could not be ascertained definitely. 

 The usual method of absorption curve analysis is not 

 applicable here, as the curves given in figure 3 depend on 



