98 Mr Dalton on the Vision of Colours. 



mit the blue excess, which causes it to appear blue; a few red 

 rays pervading the eye may serve to give the colour that fad- 

 ed appearance. In candle-light, red and orange, or some other 

 of the higher colours, are known to abound more proportion- 

 ably than in day-light. The orange light reflected may there- 

 fore exceed the blue, and the compound colour consist of red 

 and orange. Now, the red being most copiously reflected, 

 the colour will be recognized by a common eye under this 

 small modification ; but the red not appearing to us, we see 

 chiefly the orange excess ; it is consequently to us not a modi- 

 fication but a new colour. 



3. By a similar method of reasoning, crimson, being com- 

 pounded of red and dark blue, must assume the appearances 

 T have described. 



4. Bodies that arc red and scarlet probably reflect orange 

 and yellow in greatest plenty, next after red. The orange and 

 yellow, mixed with a few red rays, will give us our idea of red, 

 which is heightened by candle-light, because the orange is then 

 more abundant. 



5. Grass-green is probably compounded of green, yellow, and 

 oransre, with more or less blue. Our idea of it will then be 

 obtained principally from the yellow and orange mixed with a 

 few green rays. It appears, therefore, that red and green to 

 us will be nearly alike. I do not, however, understand, why 

 the greens should assume a bluish appearance to us and to 

 every body else, by candle-light, when it should seem that 

 candle-light is deficient in blue. 



6. The green rays not being perceived by us, the remaining 

 rays may, for aught that is known, compound a muddy red. 



7. The observations upon the phenomena of pink and crim- 

 son will explain this fact. 



8. Suppose a body to reflect red rays as the number 8, 

 orange rays as the number 6, and blue as 5 ; and another body 

 red 8, orange 6, and blue 6 : then it is evident that a common 

 eye, attending principally to the red, would see little difference 

 in those colours ; but we, who form our ideas of the colours 

 from the orange and blue, should perceive the latter to be bluer 

 than the former. 



9. From the whole of this paper it is evident, that our eyes 



