394 HISTORY OF OPTICS. 



would suggest, would require to be laid aside, 

 before he could understand Newton's theory of the 

 composition of light. 



Other objections to Newton's theory, of a kind 

 very different, have been recently made by that 

 eminent master of optical science, Sir David Brew- 

 ster. He contests Newton's opinion, that the 

 coloured rays into which light is separated by re- 

 fraction are altogether simple and homogeneous, 

 arid incapable of being further analyzed or modified. 

 For he finds that by passing such rays through 

 coloured media, (as blue glass for instance,) they are 

 not only absorbed and transmitted in very various 

 degrees, but that some of them have their colour 

 altered; which effect he conceives as a further 

 analysis of the rays, one component colour being 

 absorbed and the other transmitted 22 . And on this 

 subject we can only say, as we have before said, 

 that Newton has incontestibly and completely esta- 

 blished his doctrine, so far as analysis and decom- 

 position ly refraction are concerned ; but that with 

 regard to any other analysis, which absorbing media 

 or other agents may produce, we have no right 

 from his experiments to assert, that the colours of 

 the spectrum are incapable of such decomposition. 

 The whole subject of the colours of objects, both 

 opake and transparent, is still in obscurity. New- 



22 This latter fact has, however, been denied by other expe- 

 rimenters. 



