SOME PHYSICAL PROBLEMS 



regions. Reasoning from analogy, it may be supposed 

 that a corresponding layer of the atmosphere of other 

 stars is the one which gives us the reverse spectrum of 

 those stars. The exact composition of this layer of 

 the sidereal atmosphere must, of course, vary with the 

 temperature of the different stars, but in no case can 

 we expect to receive from the spectroscope a full record 

 of all the substances that may be present in other 

 layers of the atmosphere or in the body of the star it- 

 self. Thus, for example, the ordinary Freuenhofer 

 spectrum of the sun shows us no trace of the element 

 helium, though through other observations at the 

 time of eclipse Professor Lockyer had discovered that 

 element there, as we have seen, some thirty years be- 

 fore anything was known of it on the earth. 



In a recent eclipse photographs were taken of the 

 spectra of the lower part of the sun's atmosphere by 

 itself, and it was found that the spectrum of this re- 

 stricted area taken by itself gave the lines which 

 specialize the spectra of so different a star as Procyon. 

 "I recognize in the result," says Professor Lockyer, 

 "a veritable Rosetta Stone which will enable us to 

 read the celestial hieroglyphics presented to us in 

 stellar spectra, and help us to study the spectra and to 

 get at results much more distinctly and certainly than 

 ever before." 



But the most striking confirmation which the me- 

 teoritic hypothesis has received has come to hand 

 through study of the spectrum of the new star which 

 appeared in the constellation Perseus in February, 

 1901, and which was so widely heralded everywhere 

 in the public press. This star was discovered on the 



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