200 Experimental Philosophy. [Lecture 14. 



various pieces of silk or woollen stuff are not 

 the same by day as by candle light ; but there 

 is a common experiment which will yet more 

 forcibly illustrate what I have been observing, 

 and prove that colour is not in the objects, but 

 in the light by which they are seen. Let a pint 

 of common spirit, the cheapest will answer as 

 well as the best, be poured into a soup-dish, and 

 then set on fire : as it begins to blaze, let the 

 spectators stand round the table, and let one 

 of them throw a handful of salt into the burning 

 spirit (still keeping it stirred with a spoon). Let 

 several handfuls of salt be thus successively 

 thrown in ; the spectators will see each other 

 frightfully changed, their colours being altered 

 into a ghastly blackness. It is plain, then, that 

 the solar rays are composed of matter different 

 from the light which is emitted by this flame ; 

 and the truth is, that the light of a candle is 

 somewhat different from both. 



But the genius of Newton has enabled us to 

 go still further in ascertaining the nature of 

 light. He has analysed it with as much expert- 

 ness as a chemist analyses any physical sub- 

 stance, and has divided it into its component 

 parts. To this noble discovery the great philo- 

 sopher was led rather by accident than by de- 

 sign ; but a mind such as Newton's was able to 

 improve whatever hint chance submitted to his 

 view. It was in attempting to rectify the errors 

 arising from the aberration of light in the glasses 



