The descent of a light body resting on a heavy one
Air rushing to fill the void behind a falling solid; three margin figures
On this leaf Leonardo argues that a light body of slight thickness, merely resting on and not joined to a heavier one, will not separate from it during a natural descent unless a compound (rotating) motion intervenes. He grounds this on the principle that, since nature admits no vacuum, the air driven away by a falling body must rush back at the same speed to fill the space it leaves, and that this air, in 'dressing' the angles of a descending solid such as a cube, moves in a circular path. The right-hand leaf carries the mirror-script text with three small figures of air-invested solids drawn in the margin and a corner construction at the foot; the left fragment mounted alongside is faded and bears no transcribed writing. Numerical values 4, 3 and 1 1/3 accompany the figures.
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A light body will not part from the heavy one it rests on
A light thing of slight thickness, entirely placed upon but not joined to a heavy one, is not separated from it by any amount of their natural descent. Only if a revolution occurs in them, that is a compound motion, will the light body divide from the heavy.
Air fills the void behind a descending solid and circles its angles
Because no vacuum is given in nature, the air displaced by the falling body must run at the same velocity to fill the space it vacates. In dressing the angles of a solid the air makes a circular motion, and Leonardo speculates on where the centre of that turning is generated at the angle of the descending cube.