When a shadow lags, matches, or blurs beyond its body
The cast shadow slower than its body, equal to it, and its edges softening with distance
Continuing the science of the cast shadow, Leonardo proves that a derivative shadow can also be much slower than its primitive shadow, using a body b c moving over plane n while its shadow rests on the opposite wall d e. He shows the two motions become equal only when the light moves in step with the body, illustrated by a walker heading west whose shadow first lags ahead of him and later flees swiftly behind. A final paragraph states that a shadow's edges grow more confused the farther they are from the primitive shadow, with a lettered figure (a b, c d, e d). Two hatched pen diagrams accompany the text.
On this page
A shadow slower than its body (b c, plane n, wall d e)
Leonardo proves the derivative shadow can be far slower than the primitive. As the shadowing body b c travels the whole space c e over plane n, its shadow on the opposite wall d e barely stirs: the primitive shadow b c crosses the whole space b d while the derivative shadow does not depart from d e.
Shadow equal to body: the walker heading west
The motion of the derivative shadow equals that of the primitive only when the light moves in step with the shadowing body. Whoever walks westward from morning to evening finds his shadow, in the first part of the day, lagging slowly ahead of him, and in the last half of the day fleeing backward far faster than he goes forward.
Blurred edges of the remote shadow (a b, c d, e d)
The boundaries of the derivative shadow grow more confused the farther they lie from the primitive shadow. Leonardo begins the proof with a b as the luminous, c d the primitive shadowing body, and e d the simple derivative shadow, the demonstration continuing on the following page.
Hatched diagrams of body, wall and shadow
Two small hatched pen figures are set among the text: an upper trapezoidal figure with points n, b, c and e representing a body and the opposite wall, and a lower hatched triangle lettered b, c above and a, e, f, g below illustrating the widening shadow cast toward the ground.