1886.] New Elements in Gadolinite and Samarskite. 507 



handrail has ohtained, among others, two hands (X 573 and \ 543*2), 

 which he considers to be cansed by two elements, named respectively 

 Zac and Z/3, and which he considers new, at all events if we except 

 terbinm, and possibly the elements of what was formerly called 

 holminm. His method fails to show any spectrnm in solutions of 

 yttria which by my method give the yttria bands with the greatest 

 brilliancy ; while conversely his method shows a fluorescent spectrum 

 in solutions of earths separated as widely as possible from yttria, 

 chemically as well as spectroscopically. My experiments on both 

 these methods tend to the conclusion that our bands are not due to 

 the same cause, although M. de Boisbandran's experiments have led 

 him to the opposite conclusion. The band of Z/3 (543) falls between 

 the double green band of gadolinium (549 and 541), and the band of 

 Za (573) would come very near the citron line (574). 



A hitherto unrecognised band in the spectrum by absorption or 

 phosphorescence is not of itself definite proof of a new element, but 

 if it is supported by chemical facts such as I have brought forward 

 there is sufficient prima facie evidence that a new element is present. 

 Until, however, the new earths are separated in sufficient purity to 

 enable their atomic weights to be approximately determined, and 

 their chemical and physical properties observed, I think it is more 

 prudent to regard them as elements on probation. I should therefore 

 prefer to designate them provisionally by the mean wave-length of the 

 dominant baud. In this I am following the plan adopted by astrono- 

 mers in naming the minor planets, which are known by a number 

 encircled by a line. If, however, for the sake of easier discussion 

 among chemists a definite name is thought more convenient I will 

 follow the plan frequently adopted in such cases, and provisionally 

 name these bodies as shown in the following table : — 



Position of lines 

 in the 

 spectrum. 



Scale of 

 spectro- 

 scope. 



Mean waye- 



length of 

 band or line. 



1 



A 2 



Pro- 

 visional 

 name. 



Probability. 



Absorption-bands in \ 



f 8-270° 



443 



5096 



Da 



New. 



violet and blue . . J 



I 8-828 



475 



4432 



S/3 



New. 



Bright lines in — 













Violet 



8 515 



456 



4809 



Sy 



Ytterbium. 





8 931 



482 



4304 



Ga 



New. 



Greenish-blue (mean 













of a close pair) . . 



9-650 



545 



3367 



G/3 



Gadolinium, 













or Z£. 



9-812 



564 



3144 



Gey 



New. 





9 -890 



574 



3035 



Gd 



New, or Za. 



Yellow 



10 050 



597 



2806 



Gee 



New. 





10-129 



609 



2693 



S8 



New. 



Bed 



10-185 



619 . 



2611 



G£ 



New. 





. 10-338 



647 



2389 





New. 



