On the Chemistry of the Hottest Stars. 



187 



At that time (1873) no fluted metallic spectra, with the exception 

 of hydrogen, had been recognised, and I stated that my work had 

 not revealed any.* From that time to the present the area of inves- 

 tigation has been extended by leaps and bounds : hundreds of 

 thousands of facts have been accumulated. I propose, therefore, to 

 inquire in this concluding part of my communication whether my 

 early attempt to group the facts available nearly a quarter of a 

 century ago still holds good. 



Before, however, I refer to the results of the new work contained 

 in this memoir, having special reference to the stars, it will be neces- 

 sary to give a very hasty sketch of some of the main conclusions 

 derived from solar research, the more especially since the stellar 

 work was taken up with a view of testing the views arrived at from 

 a special study of the sun. 



When I began spectroscopic work in 1865, the general idea was 

 that the spectrum of a chemical substance was one and indivisible — 

 that it could not be fundamentally changed by temperature. 



In a paper communicated to the Royal Societyf in 1874, I alluded 

 to the evidence showing that this opinion was erroneous, and that 

 metals, including hydrogen and, as recently had been shown, J potas- 

 sium and sodium possessed fluted spectra, the line, fluting, and con- 

 tinuous spectra indicating different molecular complexities which 

 could be dissociated by heat and electricity. 



In 1878 I went further, § and showed that the solar phenomena 

 could only be explained by assuming that the changes in the various 

 intensities of lines in the line spectrum itself indicated successive 

 dissociations. I pictured the effect of furnaces of different tempera- 

 tures, and I wrote as follows : — 



"It is abundantly clear that if the so-called elements, or, more 

 properly speaking, their finest atoms — those that give us line spectra 

 — are really compounds, the compounds must have been formed at a 

 very high temperature. It is easy to imagine that there may be no 

 superior limit to temperature, and therefore no superior limit beyond 

 which such combinations are possible, because the atoms which have 

 the power of combining together at these transcendental stages of 

 heat do not exist as such, or rather they exist combined with other 

 atoms, like or unlike, at all lower temperatures. Hence association 

 will be a combination of more complex molecules as temperature is 

 reduced, and of dissociation, therefore, with increased temperature, 

 there may be no end."|| 



* « Phil. Trans.,' 1873, p. 652, vol. 163, Part 2. 

 f ' Koy. Soc. Proc.,' vol. 22, p. 374. 

 X Ibid., vol. 22, pp. 362 and 376. 

 § Ibid., vol. 28, p. 157. 

 || Ibid,, vol. 28, p. 169. 



