Mr Dalton on the Vision of Colours. 93 



ed up by the plough. When this kind of cloth loses its co- 

 lour, as other people say, and turns yellow, then it appears to 

 me a pleasant green. Very light green paper, silk, &c. is 

 white to me. 



Green by candle-light. — I agree with others, that it is diffi- 

 cult to distinguish greens from blues by candle-light ; but, 

 with me, the greens only are altered and made to approach 

 the blues. It is the real greens only that are altered in my 

 eye ; and not such as I confound with them by day-light, as 

 the brown liquids above-mentioned, which are not at all tinged 

 with blue by candle-light, but are the same as by day, except 

 that they are paler. 



Blue by day-light and candle-light. — I apprehend this colour 

 appears very nearly the same to me as to other people, both 

 by day-light and candle-light. 



Purple by daylight and candle-light — This seems to me a 

 slight modification of blue. I seldom fail to distinguish pur- 

 ple from blue ; but should hardly suspect purple to be a com- 

 pound of blue and red. The difference between day-light and 

 candle-light is not material. 



Miscellaneous observations. — Colours appear to me much 

 the same by moon-light as they do by candle-light. 



Colours viewed by lightning appear the same as by day- 

 light; but whether exactly so, I have not ascertained. 



Colours seen by electric light appear to me the same as by 

 day-light. That is, pink appears blue, &c. 



Colours viewed through a transparent sky-blue liquid, by 

 candle-light, appear to me as well as to others the same as bv 

 day-light. 



Most of the colours called drabs appear to me the same by 

 day-light and candle-light. 



A light drab woollen cloth seems to me to resemble a light 

 green by day. These colours are, however, easily distinguish- 

 ed by candle-light, as the latter becomes tinged with blue, 

 which the former does not. I have frequently seen colours of 

 the drab kind, said to be nearly alike, which appeared to me 

 very different. 



My idea of brown I obtain from a piece of white paper 

 heated almost to ignition. This colour by day-light seems to 



