16 Johnstone and BolUuood — Relative Activity 



UXr^-UX^UH-^Io ^T?a 

 12 3r 2r 32 m 



(I) UI 





Aw: — n — 



(id ui-mjx^hjx-iHjii 



~SZL TZ IE 3ZT V 



\JYMJ Z^Ac -*- 

 iz 3z: m 



It is not proposed to discuss these schemes in detail or 

 to consider at any length certain minor points involved 

 to which exception might be taken. It is, however, diffi- 

 cult to understand just what is implied by the dual 

 transformation with the expulsion of a-particles in both 

 cases which is suggested for U I in the first scheme and 

 for U II in the second. It would appear that the loss 

 of an a-particle in each case should lead to the production 

 of one and the same kind of matter, namely, to a single 

 product and not to two different products to be desig- 

 nated as U X x and U Y in one example and as Io and 

 U Y in the other. The main point under consideration 

 is, however, whether either of these schemes give us a 

 clue to the explanation of the relative activities of ura- 

 nium and radium as they have been found in our experi- 

 ments, and it may be stated that they do not, since the 

 first scheme would suggest a ratio of 1/-55 for the rela- 

 tive activities of the uranium and the radium while the 

 second scheme would imply a ratio of 1/-53 for the same 

 quantities. 



In order that Scheme I might satisfactorily apply to 

 the ratio as found by experiment it would be necessary 

 to assume that about 26 out of every 100 atoms of U I 

 were transformed in the mode leading to the production 

 of actinium. This in turn is contradicted by the relative 



