6o2 THE POPULAR SCIENCE MONTHLY. 



1 . Des 6toiles tres-brillantes oti nous ne voyons que I'hydrogene en quantite 

 enorme, et le magnesium ; 



2. Des 6toiles plus froides, comma notre soleil, oti nous trouvons : 



Ilydrog^ne + Magnesium + Sodium 



riydrogene + Magnesium + Sodium + Calcium + Fer, . . . ; 



dans ces etoiles, pas de metalloides ; 



3. Des etoiles plus froides encore, dans lesquelles tons les elements metalliques 

 sont ASSociES, oil leurs lignes ne sont plus visibles, et oti nous n'avons que les 

 spectres des metalloides et des composes. 



4. Plus une etoile est ag6e, plus Vhydrogene Hire disparait; sur la terre, nous 

 ne trouvons plus d'hydrogeue en liberty. 



II me semble que ces faits sont les preuves de plusieurs idees 6mises par vous. 

 J'ai pense que nous pouvions imaginer une " dissociation celeste,'" qui continue le 

 travail de nos fourneaux, et que le metalloides sont des composes qui sont disso- 

 cies par la temperature solaire, pendant que les elements metalliques mona- 

 tomiques, dont les poids atomiques sont les moindres, sont pr6cis6ment ceux qui 

 resistent mime a la temperature des 6toiles les plus cbaudes. 



Before I proceed further I should state that, while observations of 

 the sun have since shown that calcium should be introduced between 

 hydrogen and magnesium for that luminary, Dr. Huggins's photographs 

 have demonstrated the same fact for the stars, so that in the present 

 state of our knowledge, independent of all hypotheses, the facts may 

 be represented as follows : 



Hottest Stars .) ( H + Ca + Mg 



Sun . . V Line3^ of -I H + Ca + Mg + Na + Fe 



Cooler Stars .) (— — Mg + Na + Fe + Bi + Hg 



Fluted Spectra of 

 Coolest . Fluted bands of — — — — — — ■{ Metals and Met- 

 alloids. 



I have no hesitation in stating my opinion that in this line of facts 

 we have the most important outcome of solar work during the last ten 

 years ; and if there were none others in support of them, the conclu- 

 sion would still stare us in the face that the running down of tein- 

 perature in a mass of matter which is eventually to form a star 

 is accompanied by a gradually increasing complexity of chemical 

 forms. 



This, then, is the result of one branch of the inquiry, which has 

 consisted in a careful chronicling of the spectroscopic phenomena pre- 

 sented to our study by the various -stars. 



Experimentalists have observed the spectrum of hydrogen, of cal- 

 cium, etc., in their laboratories, and have compared the bright lines 

 visible in the spectra with the dark ones in the stars, and on this 

 ground they have announced the discovery of calcium in the sun or of 

 hydrogen in Sirius. 



' Symbols are used here to save space. II = Hydrogen, Ca = Calcium, Mg = Mag- 

 nesium, Na = Sodium, Fe = Iron, Bi =: Bismuth, Hg =: Mercury. 



