A
seconds pendulum is a
pendulum whose period is precisely two
seconds; one second for a swing in one direction and one second for the return swing.
At standard gravity its length is 0.994 m (39.1 in). This length was determined (in toises) by Marin Mersenne in 1644. In 1660, the Royal Society proposed that it be the standard unit of length. In 1675 Tito Livio Burattini proposed that it be named the meter. In 1790, one year before the metre was ultimately based on a quadrant of the Earth, Talleyrand proposed that the metre be the length of the seconds pendulum at a latitude of 45°.[1]
In 1670 the seconds pendulum was employed by William Clement in his improved version of the original pendulum clock by Christian Huygens, creating the longcase clock which could tick seconds.[2]
In 1855 the British yard was defined as a specified fraction of the length of the seconds pendulum.[3]
