RECENT DISCOVERIES IN RADIATION. 499 



radium is itself a product of the disintegration of some heavier element 

 which has been undergoing this process of decay since the world began. 



Subaiomic Energies. 

 The energy which would be required to produce such changes from 

 the simpler to the heavier atoms, and the equivalent energies which are 

 set free when the heavier atoms disintegrate into simpler ones, are 

 enormously greater than those involved in the changes which take place 

 in the constitution of molecules in the ordinary chemical transforma- 

 tions with which we have thus far been familiar. The disintegration 

 of a gram of uranium, or thorium, or radium, sets free at least a 

 million times as much energy as that which is represented in any 

 known chemical change taking place within a gram weight of any 

 known compound substance. The experiments of the last eight years 

 have then marked a remarkable advance in science in that they have 

 proved the existence of an immense store of subatomic energy. It 

 seems highly improbable, however, that this energy can ever be util- 

 ized on the earth to serve man's economic needs, for thus far we 

 know of but three substances which are disengaging it and these are 

 changing so slowly that the rate of evolution of energy is almost 

 infinitesimal. Eadium may possibly prove to be of some practical 

 value in the cure of disease, although it is too early yet to assert even 

 this with certainty. But even if no practical application of these dis- 

 coveries should be found, radio-activity will nevertheless have served 

 one of the most useful of all ends, namely, that of enlarging man's 

 knowledge of the ways of nature and of deepening his insight into the 

 constitution of matter. ■ 



