OXYGEN IN THE SUN. 17 



from the absence of the lines of particular elements from 

 the solar spectrum as in weighing the extremely important 

 discovery which has just been effected by Dr. H. Draper. 



I would specially call attention now to a point which I 

 thus presented seven years ago : " The great difficulty of 

 interpreting the results of the spectroscopic analysis of the 

 sun arises from the circumstance that we have no means of 

 learning whence that part of the light comes which gives 

 the continuous spectrum. When we recognize certain dark 

 lines, we know certainly that the corresponding element 

 exists in the gaseous form at a lower temperature than the 

 substance which gives the continuous spectrum. But as 

 regards that continuous spectrum itself we can form no such 

 exact opinion." It might, for instance, have its origin in 

 glowing liquid or solid matter; but it might also be com- 

 pounded of many spectra, each containing a large number 

 of bands, the bands of one spectrum filling up the spaces 

 which would be left dark between the bands of another 

 spectrum, and so on until the entire range from the extreme 

 visible red to the exterme visible violet were occupied by 

 what appeared as a continuous rainbow-tinted streak. " We 

 have, in fact, in the sun," as I pointed out, " a vast agglo- 

 meration of elements, subject to two giant influences, pro- 

 ducing in some sort opposing effects viz., a temperature 

 far surpassing any we can form any conception of, and a 

 pressure (throughout nearly the whole of the sun's globe) 

 which is perhaps even more disproportionate to the phe- 

 nomena of our experience. Each known element would 

 be vaporized by the solar temperature at "known pressures ; 

 each (there can be little question) would be solidified by the 

 vast pressures, did these arise at known temperatures. Now 

 whether, under these circumstances, the laws of gaseous 

 diffusion prevail where the elements are gaseous in the solar 

 globe ; whether, where liquid matter exists it is in general 

 bounded in a definite manner from the neighbouring gaseous 

 matter; whether any elements at all are solid, and if so 

 under what conditions their solidity is maintained and the 



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