214 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



It surprises me tliiit Aston considered this theory as a prophetic 

 vision of isotopy. For my part, I attribute only to chance any 

 analogy between the two theories. 



The experiments of Crookes relative to meta elements had the 

 incontestable merit of bringinf; to light a series of remarkable phe- 

 nomena then entirely novel. Would that he had then listened to 

 the wise counsel which ^Marignac gave him so diplomaticall}' and 

 courteously in the Journal of the Natural and Physical Sciences of 

 Geneva. Why did he not mind the objections with which Lecoq 

 de Boisbaudran so justly opposed his theory, and Avhich proved 

 so clearly that the phosphorescent spectra of yttrium did not belong 

 to yttrium but to impurities? The criticisms of Marignac and Lecoq 

 de Boisbaudran appear to have been met with general indifference. 

 Indeed, the theory of meta elements was very favorably received. 

 Crookes did not lack either approval or imitation, but to-day the 

 meta elements have no standing. Of the long discussion which I 

 had with Crookes on the matter, there remain to-day only the gen- 

 eral laws of cathode phosphorescence. 



The passing interpretation of the facts matters little in com- 

 parison with the real observed phenomena themselves. The work 

 of Crookes on the phosphorescence of the yttria earths is a lasting 

 monument. This we can admire without reserve, closing our ears 

 to the interpretation, I regret only that my illustrious opponent 

 lost through his mistaken theories the advantage of an important 

 discovery, for unwittingly^ he had come upon europium. - I would 

 be happy could I save this from oblivion. Crookes had observed 

 in the mixtures which contained both samarium and yttrium, and 

 which consequently should contain all the intermediate earth ele- 

 ments, a phosphorescent band which appeared to him to behave 

 in a peculiar manner. He designated it for that reason an " ab- 

 normal band." At the time he attributed it to both samarium 

 and yttrium, considering it as a resultant vibration of the atoms 

 of the two elements. Lecoq de Boisbaudran, who found several 

 analogies in certain phosphorescent spectra of solutions, which he 

 designated " reversed spectra," attributed the band to a ncAv element. 

 He said that this band " was perhaps not without relationship to 

 the abnormal band of Crookes." That is definite enough. Thus 

 Crookes was left free to vindicate himself in the discovery of tliis 

 new element. He remained contented to consider his band as char- 

 acteristic of a meta element of samarium. 



Among the earths which show^cd him the reversed band, Lecoq de 

 Boisbaudran observed a new spark spectrum; but he reserved the 

 question of deciding whether or not it was identical with the ele- 

 ment showing the "' reversed spectrum " or that which produced the 

 direct spark. 



