Balances and Weights About the Center of the World
Studies of balance beams, oscillation, oblique descent and the sun above the elemental spheres.
This crowded sheet gathers many small diagrams and notes on the statics of balances and the behavior of heavy bodies about the center of the world. Leonardo treats poles and arms of balances, the equality or inequality of their arms, and the oscillation (titubation) that dies in one arm and is reborn in the other through interrupted impetus. He distinguishes weights that descend straight toward the center of the elements from those that descend obliquely, and adds a figure of the sun above the elemental spheres, whose heat continually alters the levity and gravity of air, water and earth.
On this page
Oblique versus straight descent of a heavy body
A heavy body descending straight down weighs only toward the center of the elements, while one descending obliquely divides its natural gravity between straight and oblique motion. The more the motion approaches the straight line rather than the horizontal, the more it weighs toward the center of the world.
Oscillation of the balance and thickness of its pole
The oscillation of a balance is briefer in its time the thinner its pole. Leonardo keys the figure with the labels c, m f K, i a l, h d g, b, e, and notes that e is the center of the world.
Interrupted impetus in the balance arms
The interrupted impetus is that which dies in one arm of an oscillating balance and is reborn in the other, never returning to the magnitude of its antecedent. The oscillation does not die of itself at once, because it has as much of motion as of weight, and as much of weight as of motion.
Balance concentric with the center of the world
If the center of the balance is concentric with the center of the world b, then the weights of the balance a b will rest without oscillation at any degree of obliquity. The oscillation otherwise depends on the length of the balance beam.
The sun above the elemental spheres
Air, water and earth are continually changeable in their levity and gravity through the heat of the sun, which by heating lightens the part of the element nearest to it and does the contrary in the opposite part. A drawn sun sits above the concentric elemental spheres.
