ClipArt ETC
"A pendulum has a strong tendency to maintain its plane of oscillation, a fact that has been used in the experimental demonstration of the earth upon its axis. The chief function of the wheel-work of a clock is to register the number of vibrations of the pendulum. If the clock gains time, the pendulum is lengthened by lowering the bob, if it loses time, the pendulum is shortened by raising the bob." — Avery, 1895

Pendulum

"A pendulum has a strong tendency to maintain its plane of oscillation, a fact that has been used in…