PRESIDENTIAL ADDRESS, B.A. 1871. 169 



produced in the solar spectrum by the absorption 

 of our own atmosphere. The prism became an 

 instrument for chemical qualitative analysis in the 

 hands of Fox Talbot and Hcrschel, who first 

 showed how, through it, the old " blowpipe test " 

 or generally the estimation of substances from 

 the colours which they give to flames, can be 

 prosecuted with an accuracy and a discriminating 

 power not to be attained when the colour is judged 

 by the unaided eye. But the application of this 

 test to solar and stellar chemistry had never, I 

 believe, been suggested, either directly or indi- 

 rectly, by any other naturalist, when Stokes taught 

 it to me in Cambridge at some time prior to 

 the summer of 1852. The observational and 

 experimental foundations on which he built 

 were : 



(1) The discovery by Fraunhofer of a coincidence 

 between his double dark line D of the solar spec- 

 trum and a double bright line which he observed 

 in the spectra of ordinary artificial flames. 



(2) A very rigorous experimental test of this 

 coincidence by Prof. W. H. Miller, which showed 



