﻿Elements of the Higher Groups, 1137 



The pair 4550*8 and 4647*6 are very prominent in the 

 spectra of Novai simultaneously with strong enhanced 

 nitrogen lines 1+631+ 3!+, 4640-82. If the above considerations 

 be correct, carbon occurs in stellar spectra as C + and C ++ , 

 and the two stages follow each other in rather quick suc- 

 cession. This is to be expected of an element having a 

 large "steric factor." 



Silicon. — Lockyer t classified the lines of silicon in four 

 groups, according to their mode of production, and has 

 shown that each group is represented with the greatest 

 intensity in stars at different stages of development. The 

 following is compiled from the Harvard Annals: — 



Group I. Group II. Group III. Group IV. 



Stellar^ X -«W05f«1 X = 4131 ,„. + . \=4869 «,. + +* A = 40891 



Class.} X-390o(Si). 4128 (Sl) ' 4553 (bl } " f>740 f 



K ? — — — 



G 12* Absent. — 



F Present. Present. — — 



A — Present. — — 



B9 — 3 — — 



B6 — 3 — — 



Bo — 3 — — 



B3 — 2 1 — 



B2 — 1 2 2 



Bl — — 4 5 



BO — — 5 15 



Oc5 — — ? 12 



Oe — — . ? 6 



* Intensity in the solar spectrum on Rowland's scale. 



It is not quite certain if lines belonging to Group III. and 

 •Group IV. can be regarded as due to Si ++ and Si +++ re- 

 spectively. If Sommerfeld and KosseTs spectral displace- 

 ment law J be true, the spectrum of Si ++ ought to have the 

 same constitution as the spectrum of neutral magnesium, 

 i. e. ought to consist of triplets and singlets. Group III. 

 and Group IV. may be both regarded as due to Si + + , 

 Group III. belonging to combinations like lS-mp 2 , Group IV. 

 to stronger combinations like IS— mP. This is of course 

 only a suggestion. But there appears to be but little doubt 

 that in the stellar range available for us, silicon occurs not 



f The Si+-pair is present in the star y Oygni (FSA) and is as strong as in 

 .a Cygni (A2F) (Lockyer, Month. Not. R. A. S. 1921). In FoA stars they are 

 weakened, and entirely absent from the solar spectrum. Additional lines of 

 Group IV. at X=5740'2, 4829-4, 4820-1. 48137 have been identified by 

 •Fowler in the spectra of /3 Crucis type Bi, Monthly Notices, vol. Ixxvi. p. 196. 



I Sommerfeld, Atombau. 



