The rebound of falling bodies; the sphere of water on the earth
Water stays centered on the world though the earth shift; rebound angles of a falling weight
Two studies share the page. In the first, Leonardo reasons that the surface of the water always stays equidistant from the center of the world however the earth may shift, and that if the earth left that center the water would keep the same thickness but a smaller diameter; a small drawing shows the offset spheres of earth and water (a, b) within the air. The second, headed 'Of the rebound,' treats how a heavy body strikes a plane: a weight falling perpendicularly rebounds at unequal angles unless the central line of its gravity meets the plane, while a body striking an oblique plane rebounds at equal angles from the plane though not from its original line of motion. Three pen figures at right illustrate the falling-body cases.
On this page
The sphere of water keeps the world's center
However the earth moves, the surface of the water never leaves its sphere but stays equidistant from the center of the world. Were the earth to withdraw from that center, the water would remain around it with equal thickness but a smaller diameter than when it held the earth within its body.
Rebound at equal and unequal angles
A heavy body descending perpendicularly onto a plane rebounds at unequal angles if it does not strike with the part through which the central line of its gravity passes. A body striking an oblique plane, even falling on it in a straight line, rebounds at equal angles from the plane but not from its line of motion.