330 



Spectra of the Brighter Stars. [Dec. 8, 



(2.) Lines of iron and other 

 substances will disappear at this 

 Etage, because the bright lines 

 from the interspaces will counter- 

 act the lines in the same posi- 

 tions due to absorption of sur- 

 rounding 1 vapours. 



(3.) The chances of violent 

 collisions being now enormously 

 increased, we should expect the 

 absorption of very high-tempera- 

 ture vapours. The solar chromo- 

 spheric lines may be taken as 

 examples of lines produced at 

 such temperatures. 



(2.) In the spectrum of a 

 Cygni, which represents the 

 earliest example of this stage, 

 there are a few of the longest 

 lines of iron, but in other stars of 

 this class the iron lines disappear. 



(3.) The new lines which now 

 appear include the chromospheric 

 line at X4471, and possibly a few 

 others. 



The Hottest Stars. 



The order of the absorbing 

 layers should follow the original 

 order of the extension of the 

 vapours round the meteorites in 

 the first condition of the swarm, 

 and the lines seen bright in 

 nebulae, whatever their origins 

 may be, should therefore appear 

 almost alone as dark lines. 



In stars like <z Andromedae we 

 have absorption lines agreeing 

 in position with some of the bright 

 lines which appear in nebulae. 



Stars of Decreasing Temperature. 



Stage 1. Owing to the dimin- 

 ishing depth of the absorbing at- 

 mosphere, the hydrogen lines 

 will, on the whole, get thinner, 

 and new lines will appear. These 

 new lines will not necessarily be 

 identical with those observed in 

 the spectra of stars of increas- 

 ing temperature. In the latter 

 there will be the perpetual explo- 

 sions of the meteorites affecting 

 the atmospheres, whereas in a 

 cooling mass of vapour we get 

 the absorption of the highest 

 lavers of vapours. The first lines 



Taking Sirius as a type of 

 sta.rs in the first stage of de- 

 creasing temperature, it is found 



