A Treatise on Painting, by Leonardo da Vinci
Senex and Taylor, London
It often happens, that the illumined and shadowed Parts of the same Body, are seen of different Colours; the one, for Instance, appearing Red, and the other Green; the Body, it self, being all the while uniform and alike in its Colour, throughout. Now this is observ'd, when the Light issuing out of the East, strikes upon an Object, and tinges it with the Colour of its own Rays; another Object at the same time being placed to the Westward, of a Colour different from the first, and illumined by the same Light: In this Case, the Light reflected from the latter Object, bounding towards the East, will strike upon those Parts of the first Object, which fall in their Way; and stopping there, will communicate the Light, and Colour of the one Object, to the opposite side of the other. My self have frequently observed a white Object, with Red Lights, and blue Shadows; This being no uncommon Appearance, in Mountains cover'd with Snow, when the Sun, at his setting, paints the whole Horizon with a Redness like Flame. See Fig. 15. Tab. 1.