GIOVANNI ALFONSO BORELLI

Chapter 2. On the moments A measure of the tendency of a weight to cause rotation around a pivot point. of heavy bodies floating in a fluid.

...and thus it constitutes a horizontal pendulum. Yet I say that it is retained and suspended by the force of the hand which keeps the diaphragm A dividing wall or plate inside the mechanical drum. FG from being turned by the force of the weight operating at the center D. This is no different than if a string-pendulum original: "fune-pendulum"; a weight suspended by a cord. CD, held by a hand from below, were unable to be carried downward through the arc DE. Although the string-pendulum CD in our case is not a single continuous object tied to the center C, it nevertheless behaves exactly as if it were tied to center C, since its effort occurs along the arc DE. He who prevents the descent of the heavy body D, which can only move through the arc DE, necessarily hinders its locomotive operation. Therefore, since the fluid FAG remains completely at rest, it will not be able to push or turn the drum. It is impossible to conceive of a projectile being pushed by an object that is entirely at rest; for the thing that pushes and impels must always be affected by its own momentum and local motion The physical movement of an object from one place to another. for this purpose, so that it may be able to transfer a degree of momentum to the projectile. Since the mercury original: "hydrargyrum"; literally "water-silver" or quicksilver. FAG is entirely inert and lacks local motion, it seems altogether impossible for it to give any momentum to the projectile, which is the drum. Consequently, the drum will not be moved by local motion. By such a device, the whirling motion original: "vertiginis"; refers to the rotation of the machine. not only fails to continue forever, but it will not even begin to move. But, leaving this digression, I return to the subject.

A faint circular technical diagram from the following page is visible through the paper. It shows a wheel-like structure with radial divisions.

C 2