On Natural Motions Depending on Gravity

IO: AL. BORELLI.

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

...should touch the internal surfaces of both flat bases and the hollow curved surface of the same drum. It is necessary that, like a stopper original: "epistomium", referring to a plug or valve that creates a tight seal., that rotated diaphragm A partition or dividing wall inside the machine. closes exactly without any gap. It must prevent the exit of the water or mercury contained in the semi-cylinder A half-cylinder shape. FAG, while the remaining space GBF is filled with air or oil. Furthermore, let the mass of the whole drum be suspended on the axis C itself. This axis is fixed by two supports so that the drum can rotate freely in a plane perpendicular to the horizon.

Then, if by the strength of a hand, the handle H and the diaphragm FCG attached to it were held perpetually in a vertical position relative to the horizon, without a doubt (my friend said) we would have in such a case a perpetual imaginary balance original: "libra", a scale with arms of equal length. of equal radii ACB. This balance would be pressed by unequal weights. Specifically, the radius CA would be weighted by the mass of the mercurial or watery hemisphere FAG. Meanwhile, the opposite radius CB would be pushed down by the lighter weight of oil or air.

Because the center of gravity of these unequal weights would always fall at some point D located between C and A, the balance AB would therefore always have to bend downward toward side A. Or rather, a horizontal pendulum CD would be formed, suspended from the center C. Therefore, the pendulum would have to descend through the arc DE. However, because the heavier fluid FAG could not move downward because of the obstruction of the diaphragm FCG, which is held in a vertical position by the strength of the hand, it would follow that the entire semi-cylinder of mercury, by pressing and treading upon the curved surface of the drum AG, which is able to rotate...