Universal and Particular Light on Polished and Shadowy Bodies
Even brightness on polished surfaces, shifting lustres, and lights born of a body's own limbs
The page continues that a shadowy body's illumination varies with how much universal light reaches its parts, then treats polished bodies: the universal lights surrounding them give an even brightness across their surfaces. On polished, lustrous bodies lit by a particular light, the shadows and lustres shift place with every movement of the light or of the eye — the two being interchangeable in their effect. A final chapter explains how bodies wholly surrounded by universal light nonetheless generate particular lights in many of their parts: the limbs joined to a body interpose themselves and deprive it of much universal light, so that the light which penetrates between the limbs becomes a particular light embracing each limb's outer parts.
On this page
Universal light gives even brightness to polished bodies
The universal lights surrounding polished bodies give a universal, even brightness across the surfaces of such bodies.
Lustres shift with the moving light or the moving eye
On shadowy bodies with polished, lustrous surfaces lit by a particular light, the shadows and lustres vary place through as many sites as there are changes of the light or of the eye that sees them; the particular light may be still and the eye move, or the reverse, with the same effect.
Particular lights born from a body's own limbs
Even a body surrounded above by the sky's universal light without sun generates particular lights, because the inequality of its surface — the limbs joined to it — interposes between that light and the body, depriving it of much universal light; the light penetrating between the limbs becomes a particular light embracing each limb's outer parts.