glowing iron. We may also observe that the flames of lights at night appear redder in proportion to their distance from the eye.—Note F.
84.
Candle-light at night acts as yellow when seen near; we can perceive this by the effect it produces on other colours. At night a pale yellow is hardly to be distinguished from white; blue approaches to green, and rose-colour to orange.
85.
Candle-light at twilight acts powerfully as a yellow light: this is best proved by the purple blue shadows which, under these circumstances, are evoked by the eye.
86.
The retina may be so excited by a strong light that it cannot perceive fainter lights (11): if it perceive these they appear coloured: hence candle-light by day appears reddish, thus resembling, in