On the Chemistry of the Hottest Stars, 



201 



in both. Taking the magnesium lines by themselves then, they 

 would suggest a temperature lower than that of the spark, but re- 

 membering that 4481 is only a short line in the experimental spark, 

 it may be that its absence from the chromosphere is not so much clue 

 to low temperature as to the admixture of the magnesium with other 

 vapours. 



The intensities of the lines of calcium, iron, and magnesium, there- 

 fore, all accord with the view that the temperature of the region of 

 the chromosphere in which these vapours exist is not less than that 

 of the electric spark. 



The possible action of heat on the Sun's present Chromosphere. 



Having these unimpeachable series of facts to go upon, we have 

 first to consider what would happen if the temperature were raised. 

 We have seen that there are, in fact, in the chromosphere many 

 layers of vapours, that the thickest lines, H and K, are thickest at 

 bottom, and that if we take the lines observed in the spectra of 

 calcium, strontium" iron, magnesium, manganese, &c, the order of 

 thinning out has no known relation to the atomic weights of these 

 substances, while taking the facts as we find them, we are certainly 

 dealing simply with the power of resisting higher temperatures. 



Xow, it is only possible to consider the results produced by a 

 higher temperature on two hypotheses. The first, the usual one, 

 that the chemical elements are indestructible ; the second, that they 

 are not. 



On the first hypothesis it is difficult to say what change could 

 take place which would alter the characteristics of the spectrum very 

 widely. We have a complex mixture of the vapours of metallic 

 substances and gases with paramount calcium, hydrogen, and the 

 cleveite gases. Temperature cannot therefore vary the relative 

 intensities of the lines. H and K must always remain predominant, 

 iron must remain because it cannot be destroyed, and the quantity 

 of hydrogen and the cleveite gases present cannot be increased, their 

 lines cannot therefore become more important in the spectrum. 



It is also clear that any change of relative density on the usual 

 hypothesis cannot be brought about by an increase of temperature ; 

 this, theu, cannot alter, it cannot change the relative proportions of 

 chemical substances present in any layer, and therefore the relative 

 intensities of the lines which indicate the existence of the various 

 substances in the different layers. 



It may be said that in consequence of a more exalted temperature, 

 the hydrogen and cleveite gases may, for some reason or other, 

 escape from among the metallic vapours, and form an upper special 

 atmosphere of their own, in which, in consequence of its greater 



