THE STORY OF NINETEENTH-CENTURY SCIENCE 



scope was perfected, the photographic method, in con- 

 junction with its use, became invaluable to the chemist. 

 By this means comparisons of spectra may be made 

 with a degree of accuracy not otherwise obtainable ; 

 and in case of the stars, whole clusters of spectra may 

 be placed on record at a single observation. 



As the examination of the sun and stars proceeded, 

 chemists were amazed or delighted, according to their 

 various preconceptions, to witness the proof that many 

 familiar terrestrial elements are to be found in the ce- 

 lestial bodies. But what perhaps surprised them most 

 was to observe the enormous preponderance in the si- 

 deral bodies of the element hj^drogen. Not only are 

 there vast quantities of this element in the sun's atmos- 

 phere, but some other suns appeared to show hydrogen 

 lines almost exclusively in their spectra. Presently it 

 appeared that the stars of which this is true are those 

 white stars, such as Sirius, which had been conjectured 

 to be the hottest ; whereas stars that are only red-hot, 

 like our sun, show also the vapors of many other ele- 

 ments, including iron and other metals. 



In 1878 Mr. J. Norman Lockyer, in a paper before 

 the Royal Society, called attention to the possible sig- 

 nificance of this series of observations. He urged that 

 the fact of the sun showing fewer elements than are ob- 

 served here on the cool earth, while stars much hotter 

 than the sun show chiefly one element, and that one 

 hydrogen, the lightest of known elements, seemed to give 

 color to the possibility that our alleged elements are 

 really compounds, which at the temperature of the hot- 

 test stars may be decomposed into hydrogen, the latter 

 " element " itself being also doubtless a compound, which 

 might be resolved under yet more trying conditions. 



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