THE CHEMISTRY OP THE STARS. 173 



But useful as the method of observing the chromosphere without an 

 eclipse, which enables us 



". . . to feel from world to world," 



as Tennyson has put it, has proved, we want an eclipse to see it face to 

 face. 



A tremendous flood of light has been thrown upon it by the use of 

 large instruments constructed on a plan devised by Respighi and myself 

 in 1871. These give us an image of the chromosphere painted in each 

 one of its radiations, so that the exact locus of each chemical layer is 

 revealed. One of the instruments employed during the Indian eclipse 

 of this year is that used in photographing the spectra of stars, so that 

 it is now easy to place photographs of the spectra of the chromosphere 

 obtained during a total eclipse and of the various stars side by side. 



I have already pointed out that the chemical classification indicated 

 that the stars next above the sun in temperature are represented by y 

 Cygni and Procyon, one on the ascending, the other on the descending 

 branch of the temperature curve. 



Studying the spectra photographed during the eclipse of this year 

 we see that practically the lower part of the sun's atmosphere, if present 

 by itself, would give us the lines which specialize the spectra of y Cygni 

 or Procyon. 



I recognize in this result 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 dis- 

 tinctly and certainly than ever before. 



One of the most important conclusions we draw from the Indian 

 eclipse is that, for some reason or other, the lowest, hottest part of the 

 snn's atmosphere does not write its record among the lines which build 

 up the general spectrum so effectively as does a higher one. 



There was another point especially important on which we hoped for 

 information, and that was this: Up to the employment of the prismatic 

 camera insufficient attention had been directed to the fact that in obser- 

 vations made by an ordinary spectroscope no true measure of the height 

 to which the vapors or gases extended above the sun could be obtained ; 

 early observations, in fact, showed the existence of glare between the 

 observer and the dark moon; hence it must exist between us and the 

 sun's surroundings. 



The prismatic camera gets rid of the effects of this glare, and its 

 results indicate that the effective absorbing layer — that, namely, which 

 gives rise to the Fraunhofer lines — is much more restricted in thick- 

 ness than was to be gathered from the early observations. 



We are justified in extending these general conclusions to all the 

 stars that shine in the heavens. 



So much then, in brief, for solar teachings in relation to the record of 

 the absorption of the lower parts of stellar atmospheres. 



