20 



Mr. J. N. Lockyer. On the Classification [Apr. 12, 



associated. It is fair to assume that these stars are of a lower tem- 

 perature than our sun. 



In the same year, in a letter to M. Dumas, published in the 

 { Comptes Rendus,'* I again pointed out that, if we consider merely 

 the scale of temperature, a celestial body with flutings in its spectrum 

 would be cooler than one which had lines in its spectrum ; and I also 

 pointed out that, taking the considerable development of the blue end 

 of the spectrum in white stars as contrasted with its feeble exhibition 

 in stars like our sun, we had strong presumptive evidence to the effect 

 that the stars like a, Lyree, with few lines in their spectra, were hotter 

 than those resembling our sun, in which the number of lines was very 

 much more considerable, and I added an inference from this : " plus 

 une etoile est chaude, plus son spectre est simple." This related 

 merely, as I have said before, to the consideration of one line of 

 temperature. 



VogeVs Classification. 



In the year following my paper, the most considerable classification 

 which has been put forward of late years was published by Dr. Vogel 

 (' Astr. Nachr.,' No. 2000), who, basing his work on the previous 

 types of Secchi, and also taking into account the inference I drew 

 in my letter to Dumas, modified Secchi's types to a certain extent, 

 but always along one line of temperature, the leading idea being, as I 

 gather from many remarks made in Duner's admirable memoir, to be 

 referred to presently, that the classification is based upon descending 

 temperatures, and that all the stars included in it are supposed 

 at one time or other to have had a spectrum similar to that of 



*-Lyra3.t 



This classification is as follows : — 



* "II semble que plus une etoile est chaude, plus son spectre est simple et que les 

 elements metalliques se font voir dans l'ordre de leurs poids atomiques. Ainsi nous 

 avons : — 



" (1) Pes etoiles tres brillantes, oil nous ne voyons que l'hydrogene en quantite 

 enorvne, et le magnesium. 



" (2) Des etoiles plus froides, comme notre soleil, oil nous trovons : — 



H + Mg + Na. 



H + Mg + Na + Ca, Fe, &c. ; 



dans ces etoiles, pas de metallo'ides. 



" (3) Des 6toiles plus froides encore, dans lesquelles tous les elements metalliques 

 sont associes, oil leurs lignes ne sont plus visibles, et oil nous n' avons que les spectres 

 des metalloides et des composes. 



" (4) Plus une etoile est agee, plus l'hydrogene libre disparalt ; sur la terre, nous 

 ne trouvons plus l'hydrogene en liberte." 



f " Car selon la theorie il faudra que tot ou tard toutes les etoiles de la premiere 

 classe deviennent ue la seconde, et celles-ci de la troisieme." — (Duner.) 



