258 THE CHEMISTRY OF THE SUN. [CH. xvm. 



the coincident lines in the above table are not produced 

 by chance. 



We may conveniently sum up what has been advanced in this 

 chapter as follows : 



Attempting to picture the spectral changes brought about by 

 the action of a series of furnaces, we find that exactly such 

 changes of intensity in spectral lines as have been recorded must 

 be produced if dissociation takes place. This holds true, not only 

 for metallic vapours, but for stars ; and some predictions which 

 have been made on the strength of the hypothesis have been 

 verified. Further, a continuation of the discussion of the 

 hypothetical furnaces seems to give a vera causa for coincident 

 lines, on the assumption that some of the elements have common 

 bases, and a further consideration of the common lines observed 

 indicate that they do not appear to depend upon the presence 

 of impurities, and it is also shown that these coincident lines do 

 somehow differ in other ways from non-coincident lines taken at 

 random from the same spectra. 



