92 MR. J. SMITH ON THE ORIGIN OF COLOUR 



and I have no doubt that in the hands of skilful investi- 

 gators many things will be made plain that are at present 

 hidden and mysterious. I may^ however, repeat what I 

 have oftener than once remarked, that a wave of light 

 when it falls on a substance composed of transparent 

 plates placed at different angles to the incident light, has 

 its force decomposed by the different plates or laminae. 

 The wave or pencil, in falling on the first surface, is partly 

 reflected and partly transmitted, and the ray transmitted 

 by the first plate may be also partly transmitted and 

 partly reflected by the next, and so on any number of 

 times; but the second plate not being at an angle to re- 

 flect all the light incident on the first, performs the part 

 of shadow to the vibrations of light on the first surface; 

 and again, at another angle, the first surface may act 

 as a shadow to some other of the plates which form the 

 reflecting substance, or vice versa; causing a change of 

 colour at every change of angle, and giving to the sub- 

 stance a changeable or flitting appearance of colour. In 

 this way there is an analysis of the pencil of incident rays, 

 and thus colour is produced in a manner simdar to that 

 of our experiments. Just as our experiments deprive the in- 

 cident light of many of its rays, so do these laminae or plates 

 in a similar manner perform the same operation. They give 

 us our two elements of colour, light and no-light ; the two 

 coordinate principles, the active and the passive. 



143. When we combine the conclusions deducible from 

 these experiments with what we know of the geometrical 

 construction of some of the natural objects surrounding us, 

 we learn with what beautiful, with what sublime simplicity 

 nature performs operations which science complicates and 

 involves ; how phenomena which in the hands of a human 

 architect — in the hands of a Newton — are made to ap- 

 pear intricate and abstruse, are in reality produced with an 

 ease and an elegance — if such artistic expressions can be 



