yan. 2, 1879] 



NATURE 



199 



purities is not sufficient. I shall show in detail in a sub- 

 sequent paper the hopeless confusion in which I have 

 been landed. I limit myself on the present occasion to 

 gi\-ing tables showing how the hypothesis deals with the 

 spectra of iron and titanium. 



We find short line coincidences between many metals the 

 impurities of which have been eliminated or in which the 

 freedom from mutual impurity has been demonstrated 

 by the absence of the longest lines. 



Evidences of Celestial Dissociation 



It is five years since I first pointed out that there 

 are many facts and many trains of thought suggested by 

 solar and stellar physics which point to another hj-po- 

 thesis— namely, that the elements themselves, or at all 

 events some of them, are co7npoitnd bodies. 



In a letter written to M. Dumas, December 3, 1873, 

 and printed in the Comptes Rendus, I thus summarised 

 a memoir which has since appeared in the Philosophical 

 Transactions. 



" II semble que plus une etoile est chaude plus son 

 spectre est simple, et que les dl^ments metalliques se font 

 voir dans I'ordre de leurs poids atomiques.^ 



" Ainsi nous avons : 



" I. Des ^toiles tres-brillantes ou nous ne voyons que 

 I'hydrog^ne, en quantite enorme, et le magnesium ; 



"2. Des etoiles plus froides, corame notre Soleil, oil 

 nous trouvons : 



H + Mg + Na 



H + Mg+Na+ Ca, Fe, . . • ; 

 dans ces Etoiles, pas de metalloides ; 



" 3- Des Etoiles plus froides encore, dans lesquelles 



' This referred to the old numbers in which Mg — 12, Xa = 23. 



tons les Elements metalliques sont ASSOCl£s, ou leurs lignes 

 ne sont plus visibles, et oii nous n' avons que les spectres 

 des metalloides et des composes. 



"4. Plus une Etoile est ag^e, plus V hydrogene libre 

 disparait; sur la terre, nous ne trouvons plus d'hydrogene 

 en liberty. 



" II me semble que ces faits sont les preuves de 

 plusieurs idees ^mises par vous. J'ai pens^ que nous 

 pouvions \m.z^aiG.x MXi^'' dissociation celeste,^ c^\ continue 

 le travail de nos foiu-neaux, et que les mdtalloides sont 

 des composes qui sont dissocies par la temperature solaire, 

 pendant que les Elements metalliques monatomiques, dont 

 les poids atomiques sont les moindres, son precislment 

 ceux qui resistent, meme a la temperature des etoiles les 

 plus chaudes." 



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. Muggins' photographs have demon- 

 strated 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, the symbol indi- 

 cating the spectrum in which the lines are visible. 



Hottest Stars 'o ( H 4- Ca -f Mg 



Sun ... S ^ H + Ca + Mg -I- Na -I- Fe 



Cooler Stars ■% \ — — Mg + Na -J- Fe 4- Bi + Hg 



Coolest 



S S 



Following out these views, I some time since communi- 



