AND THE THEORY OE LIGHT, 95 



by science, does not explain the phenomena of the two 

 wafers. The phenomena of the two wafers, however, as 

 HOW developed by experiment, aiford a simple and easy 

 solution of the nature of complementary colours. When 

 any spot on the retina is affected to an unusual degree by 

 looking for some time at a vivid colour, that spot of the 

 retina gets excited beyond any other portion of the retina. 

 When, therefore, the eye is shut, the extra excitement 

 continues, and as the excitement is a vibratory excitement, 

 in the intervals shadow or rest (if I may use the expres- 

 sion) is perceived or felt, and the image becomes differ- 

 ently coloured to what it was ; and when the eye is again 

 opened the excitement remains, but the colour changes 

 with the colour of the spot on which the image is seen. 

 There is a diminution of force in the one case and an 

 augmentation of it in the other. 



My experiments, I humbly conceive, elucidate the phe- 

 nomena we have been considering. In the whole discus- 

 sion of the subject I have not been compelled to resort 

 to any supposition, to require any exercise of faith. I 

 have not even asked the belief in a single axiom. The 

 experiments have supplied axioms and arguments, and the 

 most complete analytical proof which can be given — the 

 production of phenomena which can only be explained 

 by my argument; and I think that they completely set 

 aside the theory which is based on the doctrine of the 

 different degrees of refrangibility of the rays of light, and 

 must modify to a great extent the wave theory as at 

 present taught.* 



* Where I use the expression "number of vibrations," "momentum" 

 might be thought more appropriate, but neither conveys the exact idea 

 wished to be communicated. For "increasing or decreasing force" I might 

 have used " converging or diverging rays," but these terms are used in a 

 sense not identical with the received one. The " motion of a white ray" 

 may be considered as synonymous with the " periodical interruption of a 

 white ray." 



