Blow and weight: balls in corners and a cube-doubling method
Statics of a ball in a corner, percussion at oblique angles, and two spinning spindles
This folio gathers Leonardo's studies on percussion ("the blow") and weight, opening with balls set in corners of various angles and a spherical body resting in equilibrium on a flat plane. Further notes treat water settling in an open ("supine") corner, a geometric method for combining two cubes into one, and the loss of a blow's force as its angle of impact departs from a right angle. Along the outer margin are two drawn spindles labelled for cotton or wool and a sketch of an open hand poised to catch a falling lead ball.
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A perfect sphere at rest on a perfect plane
A perfectly spherical body on a perfect plane will not move unless moved, because all its parts are equally distant from the center and it stays in balance. Leonardo likens it to a balance whose arms are equal in weight and length, which remains motionless; each half of the sphere equals the other, so it too stays still.
Blow and weight of a ball placed in a corner
For a ball set in a corner, line a b will receive at c the first degree of the weight placed upon it if line e a receives at d the first degree of the ball's blow. The upper-right diagram shows the ball with analytical lines and the labels e, d, a, c, b.
Rule of the blow and weight at an oblique angle
If ball c travels along line c b and strikes line a g, it forms triangle c a g between the line of its course and the line struck. As many times as this acute angle enters into a right angle, so many times weaker the blow will be than its flight warrants; the first degree of the blow is at line a e, the last against a c, and the mean against a f.
Making one perfect cube from two square cubes
A method for forming a single perfect square cube from two square cubes: cut one into as many small squares as are needed to cover the other exactly, as shown in a and b. The two cubes a and b are drawn, cube b marked for subdivision and cube a coated with a layer of the subdivided thickness.
Two spindles for cotton or wool
Down the outer margin are two drawn spindles: one a composite structure with a hollow cavity and a small transverse piece, the other shorter with windings of slender cord. The second is labelled "cotton or wool."
The hand receiving a falling lead weight
A sketch of an open hand waits to receive a falling lead ball. Leonardo asks: the hand in the air is not harmed catching six pounds of lead, but if the hand rests on the ground, what damage will the falling weight do to it?