206 Experimental Philosophy. [Lecture 14. 



In short, no art can alter the colour of a 

 separated ray ; it gives its tint to every object, 

 but will assume none from any ; neither reflec- 

 tion, refraction, nor any other means can make 

 it forego its natural hue ; like gold, it may be 

 tried by every experiment, but it will still come 

 forth the same. 



In whatever manner we consider the colour of 

 a single prismatic ray, we shall have new cause 

 to admire the beauties of nature. Whatever 

 compositions of colouring we form, if examined 

 with a microscope, they will appear a rude heap 

 of different colours unequally mixed. If by 

 joining, for instance, a blue with a yellow, we 

 make the common green, it will appear to the 

 naked eye moderately beautiful; but when we 

 regard it with a microscopic attention, it seems a 

 confused mass of yellow and blue parts, each 

 particle reflecting but one separate colour : but 

 very different is the colour of a prismatic ray ; 

 no art can make one of equal brightness, and 

 the more closely we examine it the more simple 

 it appears. To magnify the parts of this colour 

 would be but to increase its beauty. 



The red and orange rays, you have seen, are 

 least subject to refraction, or are least turned 

 out of their way by the interposition of the 

 glass; they are therefore, we may conclude, 

 either larger than the rest, or propelled with 

 greater force ; in technical language, they have 

 the greatest momentum. Agreeably to this we 



