THE ADVANCE OF SCIENCE 85 



this depreciatory statement we have the discovery by 

 Rutherford and others that radium is continually being 

 formed afresh, and from that particular element in con- 

 nection with which it was discovered namely, uranium. 

 Hypotheses and experiments as to the details of this 

 process are at this moment in full swing, and results 

 of a momentous kind, involving the building-up of an 

 element with high atomic weight by the interaction of 

 elements with a lower atomic weight, are thought by 

 some physicists to be not improbable in the immediate 

 future. 



The delicate electric test for radio-activity has been 

 largely applied in the last few years to ail sorts and 

 conditions of matter. As a result it appears that the 

 radium emanation is always present in our atmosphere ; 

 that the air in caves is especially rich in it, as are 

 underground waters. Tin-foil, glass, silver, zinc, lead, 

 copper, platinum and aluminium are, all of them, 

 slightly radio-active. The question has been raised 

 whether this widespread radio-activity is due to the 

 wide dissemination of infinitesimal quantities of strong 

 radio-active elements, or whether it is the natural in- 

 trinsic property of all matter to emit Becquerel rays. 

 This is the immediate subject of research. 



Over and above the more simply appreciable facts 

 which I have thus narrated, there comes the necessary 

 and difficult inquiry, What does it all mean ? What 

 are the Becquerel rays of radio-activity ? What must 

 we conceive to be the structure and mechanism of the 

 atoms of radium and allied elements, which can not 

 only pour forth ceaseless streams of intrinsic energy 

 from their own isolated substance, but are perpetu- 

 ally, though in infinitesimal proportions, changing 

 their elemental nature spontaneously, so as to give 



