446 LECTURE xxxvir. 



different thicknesses, and of those which are seen in light variously diffracted or 

 inflected, will be more conveniently examined, when we investigate the inti- 

 mate nature of light, since the general explanation of these colours, which 

 will then be given, will enable us to follow them through all their varieties, 

 with much more ease than could be done at present, without the help of some 

 theory respecting their origin. 



