HEREDITY AND RADIUM AT DUBLIN 187 



points ; and the suggestion is that the law may carry farther 

 than even the Mendelians — who had things all their own way 

 at Dublin — hoped. However, after all, the Darwinians had 

 the last word. In " the division of spoils " a sum of £30 was 

 allotted to Mr. Francis Darwin for " the study of heredity." 



Professor Curie shared with the Abbe Mendel the honours 

 of the meeting. Physicists are absorbed in radium and its 

 ancestors ; and happily one of the Presidents — not, however, 

 of the Physical but of the Geological Section — had during the 

 3'ear made an immense advance in the investigation not of 

 the properties, a knowledge of which has not been much 

 advanced by recent investigation, but of the distribution of 

 radium and uranium. It was very delightful, while Professor Joly 

 was delivering his remarkable address, to see the youthful 

 zeal and excitement of Sir Archibald Geikie, who afterwards 

 heralded " the new epoch in geology." Both the record of 

 ascertained fact and the inferences make a quite new contri- 

 bution to both geology and geography. The fact is now 

 established that uranium is the primary source of the supply 

 of radium. 



The recent discover}^ of ionium by Boltwood serves to link 

 uranium and radium, and explains why it was that those who 

 sought for radium as the immediate offspring of uranium found 

 the latter apparently unproductive, the actual relation of uranium 

 to radium being that of grandparent. But even were we 

 without this connected knowledge, the fact of the invariable 

 occurrence in Nature of these elements, not only in association 

 but in a quantitative relationship, can only be explained on a 

 genetic connection between the two. This evidence, mainly 

 due to the work of Boltwood, when examined in detail, becomes 

 overwhelmingly convincing. 



Thus it is to uranium that we look for the continuance of 

 the supplies of radium. In it we find an all but eternal source. 

 The fraction of this substance which decays each year, or 

 rather is transformed to a lower atomic weight, is measured 

 in tens of thousands of millionths ; so that the uranium of the 

 earth one hundred million years ago was hardly more than one 

 per cent, greater in mass than it is to-day. 



The supply of uranium near the surface of the earth is 

 surprisingly large. It might be expected that 



the concentration of the heaviest element known to us (uranium) 

 at the surface of the earth is just what we would not have 

 expected. Yet a simple enough explanation may be at hand in 



