in mechanics, a machine that is moved by clock-work. See CLOCK and WATCH.

Perpetual Movement. Many have attempted to find a perpetual movement, but without success; and there is reason to think, from the principles of mechanics, that such a movement is impossible: for tho', in many cases of bodies acting upon one another, there is a gain of absolute motion, yet the gain is always equal in opposite directions; so that the quantity of direct motion is never increased.

To make a perpetual movement, it appears necessary that a certain system of bodies, of a determined number and quantity, should move in a certain space for ever, and in a certain way and manner; and for this there must be a series of actions returning in a circle, otherwise the movement will not be perpetual; so that any action by which the absolute quantity of force is increased, of which there are several sorts, must have its corresponding counter-action, by which the gain is destroyed, and the quantity of force restored to its first state.

Thus by these actions there will never be any gain of direct force to overcome the friction and resistance of the medium; so that every motion being diminished by these resistances, they must at length languish and cease.