96 Mr Dalton on the Vision of Colours. 



paper were first suggested to me by one or other of the parties, 

 and found to accord with my own ideas. 



Characteristic facts of our vision. — 1. In the solar spectrum 

 three colours appear, yellow, blue, and purple. The two for- 

 mer make a contrast ; the two latter seem to differ more in de- 

 gree than in kind. 



2. Pink appears, by day-light, to be sky-blue a little faded ; 

 by candle-light it assumes an orange cr yellowish appearance, 

 which forms a strong contrast to blue. 



3. Crimson appears a muddy blue by day; and crimson 

 woollen yarn is much the same as dark blue. 



4. Red and scarlet have a more vivid and flaming appearance 

 by candle-light than by day-light. 



5. There is not much difference in colour between a stick of 

 red sealing-wax and grass, by day. 



6. Dark green woollen cloth seems a muddy red, much 

 darker than grass, and of a very different colour. 



7. The colour of a florid complexion is dusky blue. 



8. Coats, gowns, &c. appear to us frequently to be badly 

 matched with linings, when others say they are not. On the 

 other hand, we should match crimsons with claret or mud ; 

 pinks with light blues; browns with reds; and drabs with 

 greens. 



9. In all points where we differ from other persons, the dif- 

 ference is much less by candle-light than by day-light. 



III. Observations tending to point out the cause of our ano- 

 malous vision. — The first time I was enabled to form a plausible 

 idea of the cause of our vision, was after observing that a sky- 

 blue transparent liquid modified the light of a candle so as to 

 make it similar to day-light ; and, of course, restored to pink its 

 proper colour by day, namely, light blue. This was an impor- 

 tant observation. At the same time that it exhibited the effect 

 of a transparent coloured medium in the modification of colours, 

 it seemed to indicate the analogy of solar light to that result- 

 'mg from combustion ; and that the former is modified by the 

 transparent blue atmosphere, as the latter is by the transpa- 

 rent blue liquid. Now the effect of a transparent coloured 



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