THE CONCEPTION OF THE CHEMICAL 

 ELEMENT AS ENLARGED BY THE 

 STUDY OF RADIOACTIVE CHANGE 1 



THE Council of the Chemical Society have honoured 

 me with the invitation to deliver one of three lectures 

 bearing on the ultimate constitution of matter, and 

 I accepted the invitation in my desire to show how 

 greatly I appreciated it rather than with any prospect 

 of being enabled, when the time came, to say any- 

 thing on the subject which has not already been said 

 before. The problem of the ultimate constitution of 

 matter belongs to another world than that through 

 which for the past four years we have been living, 

 and although hostilities have at length ceased, and 

 we may look forward to an opportunity of resuming 

 in the future the thread of our philosophical investi- 

 gations, philosophy herself is not so easily to be 

 resumed. Novel in one sense as are the ideas intro- 

 duced into the concepts of physics and chemistry by 

 the study of radioactivity, four years' interruption 

 has made them appear rather as a remote historical 

 accomplishment than as a contemporaneous develop- 

 ment. Although no longer new, however, the more 

 as the subject matures does it become apparent that 

 these advances are of fundamental and increasing 

 importance to the chemist. 



One would perhaps have expected that on the 



1 A Lecture delivered before the London Chemical Society on 

 1 9th December 1918. 

 111 



