on Oie New Analysis of Solar Light. 155 



containing experiments from which he drew the same con- 

 clusion that I did, as appears from that letter, and from the 

 following passages in his Treatise on Light. Viewing the 

 spectrum through a piece of smalt blue glass 0*042 of an 

 inch thick, he makes the following observation : — 



" This HED (tlie innermost of the two red bancls)**is fiee from tJie slightest 

 shade o/" orange : its most refracted limit came very nearly up to the dark 

 line D in the spectrum. A small sharp black line separated this ued from 

 the YELLOW, ivhich ivas a jwettt/ ivell-defined band of great brilliancy 

 AND PURITY OF COLOUR, of a breadth exceeding that of the first red, and 

 bounded on the green side by an obscure but not quite black interval," — Art. 

 496. 



Upon this distinct and well-described observation, which is 

 precisely what I have witnessed a hundred times, Sir John 

 reasons as follows : — 



" The two reds noticed in Art. 497 have absolutely the same colour, and 

 cannot be distinguished. On the other hand, the transition from 2^ure red 

 to j>ure yelloiv, in the case there described, is quite sudden, and the co7itrast 

 of colours most stri'.ing. * * * * What then, we may ask, has become of 

 the ORANGE; and how is it, that its 2)lace is partly siipplied by red 07i one 

 side and yellow on the other ? These phienomena certainly lead us very 

 strongly to believe that the analysis of white light by the prism is not the only 

 analysis of which it admits. * * * * This idea has been advocated by Dr. 

 Brewster in a paper published in the Edinburgh Transactions, vol. ix., and 

 the same consequence appears to follow from other experiments* published 

 in the same volume of that collection." — Art. 506. 



Having had occasion in the course of the ten years subse- 

 quent to 1822 to view the spectrum through, literally, hun- 

 dreds of solid, fluid, and gaseous bodies in different combi- 

 nations, I was led to the generalisations which I have described 

 in a paper On a New Analysis of Solar Light, read to the 

 Royal Society of Edinburgh on the 21st of March ISSlf. 

 I endeavoured to prove by specific experiments that the solar 

 spectrum was compound, and capable of analysis by absorbing 

 media, and I succeeded in insulating a portion of w/iile lig/it, 

 which the prism could not decompose. But as these points 

 are not now at issue between the Astronomer Royal and me, 

 I shall make no finther allusion to them. 



Nearly three years after the reading of this paper, on the 

 6th of Jarniary ISSl', the President and Council of the Royal 

 Society made the following announcement : — 



" The President announced that the Council had resolved to award the 

 Keith Biennial Prize, for the second period, to Sir David Brewster, for his 

 paper On a New Analysis of Solar Light.", 



Being then resident in the country, I had no knowletlge 

 whatever of llie intention of the Royal Society to do mo tliis 



• Hdinburgli 'IVansactions, § 5, p. 449. 

 t Ibid. vol. xii. p. liJ3. ' 

 M2 



