“A clock has sometimes been defined to be a machine for counting the vibrations of a pendulum, and so it is; but this is hardly a correct definition…A more correct definition would be, that a clock or a watch is a machine consisting of a train of wheels turned by a weight, a spring, or any other nearly constant force, and of which the velocity is regulated by attaching to it a pendulum, balance, or fly wheel, which always vibrates or revolves nearly in the same time. And the only distinction (except the arbitrary one of mere size) between a clock and a watch is, that a watch will go in any position, but a clock only in one.”
RUDIMENTARY TREATISE ON CLOCK AND WATCH MAKING.
By E.B. Denison