212 Mr, Charles Tomlinson on 



to the fatigue of the eye the presence of the accidental 

 colour, because if this principle were true and carried ta 

 its full extent, our eyes would be unable to endure the light 

 of day, the vivid colours of nature, or even the mild light 

 of the moon for many minutes together; we should be 

 unable to judge of colour, or to contemplate coloured 

 objects : our sense of sight would, like the hungry appetite 

 soon be satisfied ; farther than this would sicken and dis- 

 tress ; and the eye, like the stomach, having taken food, 

 would require long intervals of repose for digestion ; and 

 thus the most beautiful and useful of our senses would be 

 almost valueless. The senses being formed so much at 

 variance with each other and fitted for such opposite uses, 

 we cannot, I think, compare their functions so minutely, 

 as to say, with one writer on Chromatics, that the sensibi- 

 lity of the eye becomes diminished " in the same manner 

 as the palate, when long accustomed to a particular taste 

 ceases to feel its impression." —Library of Useful Know- 

 ledge, Optics, p. 47. 



8. The great difference between my theory and all that 

 I have hitherto seen, is, that mine depends almost entirely 

 upon physical causes ; other theories upon organic causes ; 

 the effect taking place with them only when the rays reach 

 the eye without which accidental colours have no existence ; 

 but according to my theory the divisions and combinations 

 of colour occur before they reach the eye — they are in short, 

 physical effects before they can even be seen. To support this 

 view, I suppose a principle of Homo-chromatic Attraction to 

 exist in nature, by which Colorific rays of a like kind attract 

 each other ; while those of an unlike kind repel each other. 

 Amidst all the attractions which regulate and perpetuate 

 the operations of nature, it may be presumptuous to deny 

 the existence of such an attraction as I speak of; but, if 

 colour be known only as a state of matter, and, like heat 

 and electricity, its cause is still an unsolved problem, 

 surely, I do not share in the presumption in my endeavours 

 to support this principle by facts, which have long clashed 

 with each other most discordantly, and which, admitting 

 the principle of homo-chromatic attraction, are united into 

 one distinct branch of science, harmonious, beautiful and 

 extensive. 



