 The seconds pendulum (also called the Royal pendulum), 0.994 m (39.1 in) long, in which each swing takes one second, became widely used in quality clocks.The long narrow clocks built around these pendulums, first made by William Clement around 1680, became known as grandfather clocks.The increased accuracy resulting from these developments caused the minute hand, previously rare, to be added to clock faces beginning around 1690.