Parallel figures compared, and the law of motion
Wavy and straight parallels boxed together, plus two 'Conception' notes that a moving body leaves as much space as it gains
The page pairs two boxed diagrams of parallel lines—a wavy band above and a straight band below—asserting that the straight parallel d e f equals the wavy surface a b c, 'by the fifth of the ninth.' A second, subdivided pair states that the proportion of base c to base f is the same as that of surface o to surface g. Two marginal notes headed 'Conception' treat motion: everything that moves gains as much space as it leaves, and separating two touching bodies opens a gap equal to the motion of the receding part.
On this page
Wavy and straight parallels equated
Two boxed strips set a wavy band (a, b, c) above a straight band (d, e, f). Leonardo states that the parallel d e f is equal to surface a b c, 'by the fifth of the ninth,' matching a rectified curve to its straight counterpart.
Proportion of bases and surfaces
In a second, subdivided pair the partitions are marked along the upper border. The proportion that base c has with base f is said to be the same as that which surface o has with surface g.
Conception: space gained equals space left
A marginal note headed 'Conception' states that for every thing that moves, the space that it acquires is as much as that which it leaves.
Conception: separation opens an equal gap
A second 'Conception' argues that when one thing is removed from its contact with another, the quantity of motion made by the part opposite the contact equals the distance interposed between the parts that previously touched.