Distance from the Original Light Sets the Derived Shadow
A body embraced by more of the sky's light casts the shorter shadow
Leonardo turns from point-lights to the broad original light of the sky. He asserts that bodies nearer to or farther from their original light make their derived shadow more or less short, confirming it by experiment: body m n is embraced by more light than body p q. A large sector diagram represents the sky, marked v c a b d x, from which two spheres below cast shadow cones of unequal length. The passage breaks off as he begins to define s t as a window admitting the light.
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Nearness to the original light shortens the derived shadow
Bodies nearer to or farther from their original light make their derived shadow more or less short. Experiment confirms it, since body m n is embraced by more of the light than body p q. Let v c a b d x be the sky that makes the original light, and s t a window through which it enters.
Diagram of the sky's arc casting two shadow cones
A wide sector at the top, labelled with B, D, A and C at its rim, represents the arc of sky serving as the original light. Below it two spheres are drawn one above the other, each throwing a shaded triangular shadow cone downward, the more distant sphere casting the longer cone.