1886.] New Elements in Gadolinite and Samarskite. 505 



presence of yttria was not necessary to bring it out, although by 

 deadening the brightness of the other bands it was useful, ^ not 

 seeming to affect the line 609. Several circumstances, however, 

 tended to show that although line 609 accompanied samarium with the 

 utmost pertinacity, it was not so integral a part of its spectrum as the 

 other red, green, and orange lines. For instance, the chemical as well 

 as physical behaviour of these line-forming bodies was different. On 

 closely comparing the spectra of specimens of samaria from different 

 sources, line 609 varied much in intensity, in some cases being strong 

 and in others almost absent. The addition of yttria was found to 

 greatly deaden the red, orange, and green lines of samarium, while 

 yttria had little or no effect on the line 609 ; again, a little lime 

 entirely suppressed line 609, while it brought out the samarium lines 

 with increased vigour. Finally attempts to separate line 609 from 

 samarium and those portions of the samarskite earths in which it 

 chiefly concentrated resulted in sufficient success to show me that, 

 given time enough and an almost inexhaustible supply of material, a 

 separation would not be difficult. 



But what was then practically impossible to me, restricted by limited 

 time and means, Nature has succeeded in effecting in the most perfect 

 manner. I had been working on samarskite, and many observations 

 had led me to think that the proportion of band-forming constituents 

 varied. slightly in the same earth from different minerals. Amongst 

 others, gadolinite showed indications of such a differentiation, and 

 therefore I continued the work on this mineral. Very few fractiona- 

 tions were necessary to show that the body giving line 609 was not 

 present in the gadolinite earths, no admixtures of yttria and samaria 

 from this source giving a trace of it. It follows, therefore, that the 

 body whose phosphorescent spectrum gives line 609 occurs in samar- 

 skite, but not in gadolinite; thus it cannot be due to samarium, 

 yttrium, or a mixture of these two elements ; the only other probable 

 alternative is that the source of this line is a new element. 



Chemical fractionation is very similar to the formation of a spec- 

 trum with a very wide slit and a succession of shallow prisms. The 

 centre portion remains unchanged for a long time, and the only 

 approach to purity at first will be at the two ends, while a consider- 

 able series of operations is needed to produce an appreciable change 

 in the centre. 



During the later fractionations of the yttria earths another set 

 of facts, formerly only suspected, have assumed consistent form. The 

 spectrum bands which hitherto I had thought belonged to yttria soon 

 began to vary in intensity among themselves, and continued fractiona- 

 tion increased the differences first observed. It would exceed the 

 limits of a preliminary note were I to enter into details respecting the 

 chemical and physical reasons which lead me to the definite conclu- 



