Manchester Memoirs, Vol. xlviii. (1904), No. 8. 37 



theory Giesel's result may be translated to mean that 

 polonium is produced from radium and deposited from 

 the solution on bismuth, platinum, and palladium. He 

 further found that the radioactive deposit was formed on 

 a wire held in the air above the solution, which is in accord- 

 ance with the above conclusion that polonium is produced 

 from the matter causing the induced activity, which 

 itself is produced from the emanation which would diffuse 

 into the air above a radium solution. But as the residual 

 activity so produced certainly in my experiments gave j3 

 rays, although in feeble intensity, some doubt is thrown 

 on the whole result and whether the activity on the metals 

 left in the solution was also completely free from /3 

 radiation. This explanation, therefore, cannot be regarded 

 as quite proved at the present time. 



If the time of our observations could be extended 

 from a few years to a few thousand years, the arguments 

 advanced for polonium would apply with equal force to 

 the case of radium. This element, from its known rate 

 of change, must also be a transition-form, and its present 

 existence can only be accounted for on the view that it is 

 being reproduced in the minerals as fast as it disintegrates. 

 I have been conducting some experiments during the 

 past year to try to determine experimentally whether a 

 quantity of uranium, originally free from radium, would 

 not grow a crop of the latter element in the course of 

 time. But the experiments have hardly been carried on 

 long enough at present to furnish conclusive results. 

 Many objections, it is true, can be urged against the 

 view, but it remains to be seen whether they are real or 

 apparent. There is one very great unknown factor in 

 these considerations, and that is actinium. Until this 

 element becomes available for exact study, the possibilities 

 that have to be taken into account in attempting to 



