The surfaces of hard bodies are surrounded by various qualities of light and shadow. The lights are of two sorts; one is called original, the other derivative. The original light is that which comes from the sun, or the brightness of fire, or else from the air. The derivative is a reflected light. But to return to our definition, I say, there can be no reflexion on that side which is turned towards any dark body; such as roofs, either high or low, shrubs, grass, wood, either dry or green; because, though every individual part of those objects be turned towards the original light, and struck by it; yet the quantity of shadow which every one of these parts produces upon the others, is so great, that, upon the whole, the light, not forming a compact mass, loses its effect, so that those objects cannot reflect any light upon the opposite bodies.