122 



Sir Norman Lockyer. 



tion that with such a tremendous outburst we should expact the original 

 invisible swarm to have been (very rapidly) advanced to a considerable 

 condensation at the locus of impact, and therefore to resemble some 

 " star " which had (slowly) arrived at a position pretty high up on the 

 ascending temperature curve in the ordinary course of evolution on the 

 meteoritic hypothesis. 



A comparison of the bright lines recorded by Campbell* and Vogelf 

 in the spectrum of Nova Aurigse with the strongest lines of cc Cygni — 

 a very detailed record of the spectrum of which star has been 

 recently compiled here — shows that there is a close agreement 

 between the two sets of lines. These strong a Cygni lines are almost 

 without exception the representatives of "enhanced" lines of some of 

 the metals j chiefly Fe, Ti, Cr, Ni, Ca, Sr, and Sc. If we exclude the 

 lines of hydrogen from those which were recorded in the spectrum of 

 Nova Aurigse, there remain forty-four lines for comparison. Thirty of 

 these, or about 70 per cent., agree approximately in position with either 

 strong "isolated lines or groups of lines in the spectrum of a Cygni. 



It may be assumed that, taking into consideration the brdad nature 

 of the Nova lines, if there be any genuine connection between them and 

 the lines of a Cygni, any close groups of separately distinguishable 

 lines in the latter spectrum would be thrown together in the Nova 

 spectrum, and appear as broad bands. A good instance of this appears 

 in Campbell's list. He records a band extending from XX 4534 to 

 4501. In the spectrum of a Cygni there is a strong line at each of the 

 positions given, and between them there occurs a strong quartet of 

 lines. The former are well enhanced lines of titanium, and the latter 

 of iron. It seems extremely likely, therefore, that the six lines thrown 

 together produce the apparently continuous band observed by 

 Campbell. 



If the stage of a Cygni has really been reached, the following con- 

 siderations come in : — 



In the orderly condensation of swarms, according to the meteoritic 

 hypothesis, the earlier stages are — 



A f Dark lines, corresponding chiefly "with 



Cygman < . ' , 1 „ c . J 



6 L the enhanced lines ot various metals, 



j- * 



-r> t ■ f Dark lines, comprising both arc and 



rolarian •{ , ' 1 °. 



I enhanced lines ot various metals. 



r Dark lines, chiefly corresponding to 



Aldebarian < those which appear in the arc spectra 



L of various metals. 



r Mixed bright and dark flutings and dark 



Antarian < lines. Bright lines of hydrogen in 



I those stars which are variable. 



Nebula Bright lines. 



* ' Ast.-Phys. Jour.,' vol. xi, p. 807, 1892. 

 f 'Ast.-Phys. Jour.,' vol. xii, p. 912, 1893. 



