On the Chemistry of the Hottest Stars. 



205 



Front's Hypothesis. 



This result teaches us that Prout's hypothesis, though at the time 

 it was promulgated it was a magnificent approach to the truth, cannot 

 be true absolutely, for two reasons. (1) Gras X and helium take 

 precedence, in all probability, of hydrogen (excluding the new form) 

 in the evolutionary series ; and (2) terrestrial hydrogen, as we know 

 it, is broken up molecularly before it can give as the line spectrum, 

 and it is the hydrogen that gives us the line spectrum that makes its 

 appearance in stars in greater quantity as the enhanced iron lines 

 disappear in consequence of the action of a higher temperature. 



Final Result. 



The above conclusions, based upon laboratory, solar, and stellar 

 evidence, all tending in the same direction, may be regarded as the 

 result obtained so far in regard to the "celestial dissociation" 

 which I pictured to myself in 1873. 



I claim that each step in the work has demonstrated the truth, of 

 that hypothesis more and more, and that we can now acknowledge 

 that the phenomena of the inorganic world are dominated by an 

 evolution not less majestic, although much more simple, than that 

 now universally accepted in the case of organic nature. 



XII. — General Conclusjons. (March 20, 1897.) 



1. In a mixture of vapours at a particular temperature, a vapour 

 which is not present in sufficient quantity to show all the lines of its 

 spectrum will be represented by the lines which are longest in its 

 spectrum at the particular temperature in question. 



Only some of the short lines in metallic spectra represent the 

 effects of high temperature. 



2. Some of the substances which have been investigated, including 

 iron, calcium, and magnesium, have probably a definite spectrum, 

 consisting of a few lines, which can only be completely produced at a 

 temperature higher than any which is at present available in labora- 

 tory experiments. The lines constituting the new spectra are those 

 which either only appear in the spark spectrum, or are lengthened in 

 passing from the arc to the spark. Such lines are termed enhanced 

 lines. 



3. In the case of iron, calcium, and magnesium, there are four 

 distinct temperature steps which are marked by spectral changes : 

 (a) The flame spectrum, (b) the arc spectrum, (c) the spark spec- 

 trum, (d) a spectrum consisting solely of those lines which are 

 enhanced in passing from the arc to the spark. 



