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CHAPTER IX. THE STELLAR EVIDENCE. 



I NEXT proceed to consider whether the views which I found 

 necessary to enable me to group together harmoniously and con- 

 tinuously solar phenomena years ago when nothing was known of 

 stellar chemistry, are weakened or strengthened by the study of the 

 enormous new field of investigation opened out by the recent stellar 

 work, by which we have finally the sun taking its place as one term in a 

 long series, the complete study of which enables us to watch the work- 

 ings of the celestial evolution which has built up the heavens as we 

 know them. 



The great increase of our knowledge we have gained from the 

 study of stars arises from the fact that they have revealed to us a 

 continuous series of spectral changes at temperatures much higher 

 than the sun affords us. 



One of the minor advantages of this is, that we can, taking the sun 

 as our base, see what would happen if the sun were to become hotter. 

 Let us consider this point first. 



In approaching this part of the subject, it is necessary to proceed 

 with great caution, since the things observed are different. The solar 

 work has consisted in observing different parts of the sun, the star 

 work puts us in presence of the total effects both of radiation and 

 absorption in the case of each body observed. 



The facts with regard to the lower portions of the solar atmosphere 

 have already been detailed. They have been gathered from the 

 photographs secured during the eclipse of 1898. 



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

 found that the absorption indicated by the Fraunhofer lines is not 

 caused by the chromosphere, and that the most valid absorbing layer 

 lies above the chromosphere. We have also seen that in the chromo- 

 sphere we find enhanced lines among the Fraunhofer lines, which are 

 chiefly arc lines. What must happen then if the sun is supposed to get 

 hotter 1 



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 Fraunhofer spectrum 



