186 



Mr. J. Norman Lockyer. 



in importance with the increase of stellar temperature in the stars I 

 have so far discussed. 



For instance, if such hotter stars were found we might expect that 

 either hydrogen or the cleveite gas lines would thin out and then 

 disappear first, as the iron lines thin out in Rigel and disappear in 

 Bellatrix, and that they would be replaced by other lines. 



As a matter of fact, the hottest stars under discussion do contain 

 other lines besides those of hydrogen and the cleveite gases. 



XI. Beaeing op the New Results on the Dissociation 

 Hypothesis, 



§ 1. Historical Statement. 



It was in 1873 that I first called the attention of the Society to the 

 very remarkable facts which had been even then got together regard- 

 ing the possible action of heat in the sun and stars. Referring 

 more especially to the classification of stars by Rutherfurd and 

 Secchi, I wrote as follows : — * 



"I have asked myself whether all the above facts cannot be 

 grouped together in a working hypothesis which assumes that in 

 the reversing layers of the sun and stars various degrees of ' celes- 

 tial dissociation ' are at work, which dissociation prevents the coming 

 together of the atoms which, at the temperature of the earth and at 

 all artificial temperatures yet attained here, compose the metals, the 

 metalloids, and compounds." 



Subsequently in a private letter to M. Dumas, who took the 

 keenest interest in my solar work, I wrote, " II semble que plus une 

 etoile est chaude plus son spectre est simple." 



I also pointed out the close relation of hydrogen to calcium, 

 magnesium, and other metals (it was on this ground that I had 

 named the substance which gave D 3 , which always varied with 

 hydrogen, helium), and the absence of all other terrestrial gases 

 from the solar spectrum. An interesting discussion at the Paris 

 Academy of Sciences was thus concluded by M. Dumas : — 



" En resume, quand je soutenais devant l'Academie que les 

 elements de Lavoisier devaient etre considered, ainsi qu'il avait etabli 

 lui-meme, non comme les elements absolus de l'univers, mais comme 

 les elements relatifs de Texperience humaine ; quand je professais, 

 il y a longtemps, que Vkydrogene etait plus pres des metaux que de 

 tonte autre classe de corps; j'emettais des opinions que les decou- 

 vertes actuelles viennent confirmer et que je n'ai point a modifier 

 aujourd'hui."f 



* ' Phil. Trans.,' vol. 164, Part 2, p. 491 (reproduced in ' Chemistry of the Sun,' 

 p. 201). 



t « The Chemistry of the Sun,' p. 205. 



