y-Rays of Thorium and Actinium , 



153 



In Disposition 2 the curve is the more continuously convex 

 to the origin. For both dispositions the ratio of the absorp- 

 tion coefficients is about 1 : 1*9 for Class II. bodies, and the 

 effect of hardening the zinc is the same, the value of X being 

 reduced to 80 per cent. But the actinium rays are, rela- 

 tively to radium, hardened more in Disposition 5 than in 2. 

 Grodlevvski concluded that the actinium 7-rays have only 

 one-tenth of the penetrating power of the harder 7-rays of 

 radium. As in the case of uranium X, however, work with 

 more active preparations over greater ranges has reduced 

 this difference, though actinium is still far removed in this 

 respect from the other y-ray sources examined. 



.Some Generalizations ivith regard to y-Rays. 



The results for actinium help to accentuate several relation- 

 ships which exist between the penetrating power of the 7-rays 

 of the radio-elements in solid bodies and other properties 

 they possess. There is obviously an intimate connexion 

 between penetrating power, abnormality of absorption by 

 lead and hardening by lead. The rule is — the greater the 

 penetrating power of the ray, tbe less abnormal is the absorp- 

 tion by lead as compared with that of Class II. bodies, and 

 further the less hardening effect has lead on the rays sub- 

 sequently absorbed by Class II. bodies. In Disposition l y 

 however, thorium D is an exception. 





Thorium 

 D. 



Radium 

 C. 



Mesotho- 

 rium 2. 



Uranium 

 X. 



Actinium 

 C. 



X/d Lead 



X/d Class 11. ^Position 1 .. 



1-28 



1-10 



1-28 



1-35 



X/d Lead 



X/d Class II. Dls P° sltl0n 2A . 



0-95 



1-07 



1-28 



— 



1-93 



X/d Lead 



X/d Class II. ^position 2B. 



1-03 

 1-08 



1-16 



1-40 



— 



— 



X/d Class II. (Disposition 2 A) 

 X/d Class 11. (Disposition 2D). 



112 



112 - 



— 



125 



Again, as regards penetrability, there is far more con- 

 nexion between the 7-ray and the a-rays preceding and 

 following it in the disintegration series, than there is between 



