132 Dr Hunt, Celestial Chemistry [Nov. 28, 



Benjamin Brodie, whose only publication on the subject, so far as 

 I am aware, was his lecture of 1867, unknown to me until its 

 reprint in 1880. 



It was at the grave of Priestley, in 1874, that I for the second 

 time considered the doctrine of celestial dissociation, commencing 

 with an account of the hypothesis put forward by F. W. Clarke of 

 Cincinnati, in January, 1873 1 , to explain the growing complexity 

 which is observed when we compare the spectra of the white, 

 yellow and red stars ; in which he saw evidence of a progressive 

 evolution of chemical species by a stoichiogenic process from more 

 elemental forms of matter. I then referred to the farther develop- 

 ment of this view by Lockyer in his communication to the French 

 Academy of Sciences in November of the same year, wherein he 

 connected the successive appearance in celestial bodies of chemical 

 species of higher and higher vapour-densities with the speculations 

 of Dumas (and Pettenkofer) as to the composite nature of the 

 chemical elements 2 . I then quoted from my lecture of 1867 the 

 language already cited to the effect that dissociation by intense 

 heat in stellar worlds migdit 2five us more elemental forms of mat- 

 ter than any known on earth, and farther suggested that the green 

 line in the spectrum of the solar corona, which had been supposed 

 to indicate a hitherto unknown substance, may be due to a " more 

 elemental form of matter, which, though not seen in the nebulae, 

 is liberated by the intense heat of the solar sphere, and may 

 possibly correspond to the primary matter conjectured by Dumas, 

 having an equivalent weight one fourth that of hydrogen." The 

 suggestion of Lavoisier that " hydrogen, nitrogen and oxygen, with 

 heat and light, might be regarded as simpler forms of matter from 

 which all others are derived" was also noticed in connection with 

 the fact that the nebulae, which we conceive to be condensing into 

 suns and planets, have hitherto shown evidences only of the 

 presence of the first two of these elements, which, as is well 

 known, make up a large part of the gaseous envelope of our planet, 

 in the forms of air and aqueous vapour. With this I connected 

 the hypothesis that our atmosphere and ocean are but portions of 

 the universal medium which, in an attenuated form, fills the 

 interstellary spaces ; and farther suggested " as a legitimate and 

 plausible speculation," that " these same nebulae and their result- 

 ing worlds may be evolved by a process of chemical condensation 

 from this universal atmosphere, to which they would sustain a 

 relation somewhat analogous to that of clouds and rain to the 

 aqueous vapour around us 3 ." 



1 Clarke, "Evolution and the Spectroscope," Popular Science Monthly. New 

 York, Vol. ii. p. 32. 



2 Lockyer, Comptcs Rendus, Nov. 3, 1873. 



3 A Century's Progress in Theoretical Chemistry, being an address at Northum- 



