202 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1925 



I hope is passing, does not attribute to you the fatherhood of it, but 

 ■when the history of the element is written completely and impar- 

 tially, full credit will be given to your name. 



With Crookes you knew the phosphorescent elements in the cath- 

 ode rays; with Lecoq de Boisbaudran, you saw those revealed by 

 the induction spark. In the arc spectrum you witnessed the birth of 

 luticium. With Ramsay you saw the ninth column come into the 

 classification of Mendeleeff, for the existence of which you have vic- 

 toriously fought. In helium, neon, argon, krypton, and xenon you 

 knew the astonishment which the existence of chemically inert ele- 

 ments aroused. 



At that time we considered our chemical elements eternal, immut- 

 able. Doubtless we need not have been deeply philosophical to have 

 recognized in the doctrine of Mendeleeff the thread of an evolution- 

 ary theory such as then dominated science and of which Lamarck and 

 Darwin were the promoters. Was Mendeleeff really an evolutionist 

 as to the chemical elements? I would not dare to affirm it, not 

 having read all that this genial Slav scientist has written. I have 

 known him only through what has been more or less correctly trans- 

 lated into French. But you should know and doubtless are the only 

 one who could settle the point. On my part I have always thought 

 that he was. For how can one know the analogies which Mendeleeff 's 

 table brings into relief, how recognize the family traits, those inti- 

 mate relationships of chemical characters and physical properties, 

 without supposing some mode of birth which requires certain ele- 

 ments to be like brothers and certain others to be like more distant 

 relatives? Have not you and Mendeleeff added something to science 

 which is not read in the printed text but which may be read between 

 the lines? I am disposed to see here the source of that contagious 

 enthusiasm which the periodic system has inspired in you. You 

 should have been prepared to admit that chemical elements are born 

 and die. But before photography and electrometry had given, 

 through H. Becquerel, Pierre and Mme. Curie, their marvelous dis- 

 covery of the radioactive elements, the evolution of elements could 

 have been only a philosophical hypothesis with no real experimental 

 foundation. With radium transforming into the gas radon, with 

 radon in turn changing into other new elements themselves radio- 

 active, the hypothesis of the evolution of the elements becomes a 

 reality. The chemical elements lose their immutability, are no longer 

 dead as considered by the scientists of the era just passed. They 

 enter into an active life. 



The old philosophical dream of our medieval ancestors comes from 

 the distant past into a wonderful reality. We would be tempted 

 to cry " miracle " were we not preoccupied with consigning to the 



