236 



On Radiant Matter Spectroscopy. 



[Feb. 25, 



II. " On Radiant Matter Spectroscopy : Note on the Earth Ya." 

 By William Crookes, F.R.S. Received February 18, 

 1886. 



Among the samarskite earths which concentrate towards the 

 middle of the fractionations there is one (or a gronp) which presents 

 in the radiant matter tube a well marked phosphorescent spectrum 

 differing from those I have already described. 



The measurements of the bands and lines are given below : — 



Scale of 



X. 



1 



Remarks. 



spectroscope. 



X 2 



1U oaq 







Approximate centre of a red. band, 

 shaded off on the least refran- 

 gible side. 



10*310 



6415 



2430 



Somewhat sharp edge of the red 

 band. 



10-185 



6189 



2611 



Approximate centre of a very 

 faint orange band. 



10 -130 



6094 



2693 



A sharp narrow orange-red line. 



10 -050 



5970 



2806 



Approximate centre of a narrow 

 bright orange band. (Between 

 this line and 2693 is a fainter 

 semi- continuous orange band.) 



9-840 



5676 



3104 



Approximate centre of a narrow 

 bright green band. 



9-790 



5613 



3174 



Approximate centre of a narrow 

 green band, not quite so bright 

 as 3104. 



9-690 



5495 



3312 



Approximate centre of a bright 

 green band, wider than the 

 other three green bands. 



9-610 



5406 



3422 



Approximate centre of a narrow 

 bright green band. 



The accompanying figure gives the spectrum drawn to the — scale. 



210 230 250 2 



! 1 J ■:■ 



70 290 310 330 350 370 390 



1 1 1 1 I 





T 



j 





I 



The earth giving the above spectrum, when sufficiently purified, 

 presents all the characteristics of the earth discovered by Marignac, 

 and provisionally called by him Ya.* Through the kindness of M. de 

 * " Comptes rendus," xc, p. 899. 



