How a struck cube dilates into a circle
The theory of the blow: matter spreads equally from the centre, turning a square body round
This densely written page sets out Leonardo's theory of impact: a cube of equal sides and angles, when struck by a blow, dilates equally in all directions from its centre and so tends toward a 'more perfect circle.' He imagines the centre as a sphere clothed by successive spheres, so that when the body is compressed every part moves outward along lines of equal length directed toward the centre, and the straight edges are converted into curves. The corners left outside the sphere open out and thicken until the whole body is turned into a circle. A small circle-with-cross figure at the top right accompanies the argument.
On this page
A blow dilates the cube equally from its centre
The whole thickness of the cube that spherically surrounds its centre is what, under the blow, dilates with equal circulation from that centre. Every part is moved outward by equal amounts, so that the body swells uniformly and its right angles and sides are consumed as the growing round figure absorbs them.
Straight edges converted into curves
Leonardo pictures the centre as spherical, clothed by one sphere after another. When the body is pressed, the lines of motion from its fleeing extremities are all of equal length and point circularly toward the centre; the straight sides obey and are converted from straight lines into curves, until the whole becomes a circle.
