TRANSACTIONS OF SECTION B. 



589 



to be more conveDieut, I -will follow the plan frequently adopted in such cases, and 

 provisionally name these bodies as sho-wn in the following table : — 



The initial letters S and G- recall the origin of the earths respectively from 

 samarskite and gadolinite. 



Not only has yttrium been split up by subjection to fractionation, but samarium, 

 as I have hinted above, is likely to prove equally unable to resist this operation. 

 In the phosphorescent spectrum of samarium sulphate the line S8 (609) is one of 

 the constituent. AVhen yttria is added to samaria this line is developed in greater 

 intensity, as yttria has the power of deadening the other bands of samarium, while 

 it does not seem to affect the line SS. Several circumstances, however, tend to 

 show that although line SS accompanies samarium with the utmost pertinacity it 

 is 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 is different. On closely comparing the spectra of specimens of samaria from 

 different sources, line SS varies much in intensity, iu some cases being strong and 

 in others almost absent ; the addition of yttria is found greatly to deaden the red, 

 orange, and green lines of samarium, while yttria has little or no effect on the line 

 SS ; again, a little lime entirely suppresses line Sd, while it brings out the samarium 

 lines with increased vigour. Finally, attempts to separate line SS from samarium 

 and those portions of the samarskite earths in which it chiefly concentrates has 

 resulted in sufficient success to show me that, given time enough and an almost in- 

 exhaustible supply of material, a separation would not be difficult. These facts, 

 together with the peculiar behaviour of the lines Ge and G-y, strengthen my sus- 

 picion as to the resolvability of samarium. 



Samaria giving the line S6 has been prepared from cerite and samarskite. 

 Many observations have led me to think that the proportion of band-forming con- 

 stituents varies 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 fractionations were necessary to 

 show that the body giving line SS 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 S8 occurs in 

 samarskite and cerite, but not in gadolinite. 



It now became an interesting enquiry whether all these constituents of yttrium 

 were imited together in exactly the same proportion in every case. A glance at 

 the diagram before you will show that yttrias from different sources, although 

 they may be alike as far as our coarser chemical tests are concerned, are not built 

 up exactly in the same manner. Thus, when the samarskite yttrium was forming, 

 all the constituent molecules— which 1 have provisionally named Ga, G/3, G-y, G8, 

 Ge, QC, G7, and S5— condensed together in fair proportion. In gadolinite yttrium 

 the constituents G^ and GS are plentiful, Gf is very deficient, SS is absent, and 

 the others occur in moderate quantities. In the yttrium from xeuotime GS is 

 most plentiful, G^ occurs in smaller proportion, G^ is all but absent, and SS is 

 quite absent. Yttrium from monazite contains G/3 and GS, with a fair proportion 



