42 SODDY, Evolution of Matter by Radio-active Elements. 



As science has advanced, the limitations of the universe 

 with reference to the extent of its past and future existence 

 have been forced steadily back. By the discovery of radio- 

 activity and the revelation that has followed, of the vast 

 and hitherto unsuspected stores of energy associated with 

 the atomic structure of the more complex forms of matter, 

 the possibilities of its life in both directions have been 

 enormously extended. The extension in the present 

 state of knowledge cannot, however, be regarded as 

 anything more than of the nature of a reprieve. The 

 end has been postponed, not avoided. In spite of 

 these advances cosmical history still opens with a 

 mysterious origin and closes with the pronouncement of 

 an inevitable doom. None will believe that the last word 

 has yet been spoken. There is at least a dawning probk- 

 bility that by further discoveries the two insoluble enigmas 

 of philosophy may be avoided, and that ultimately the 

 universe may be regarded as a truly conservative system, 

 limited with respect neither to the future nor the past, but 

 proceeding through continuous cycles of evolution. 



