Model of Galileo's pendulum clock, c 1642.

This 19th century model is based on a drawing by Galileo's friend and biographer, Viviani, of an incomplete pendulum clock which Galilei Galileo (1564-1642) designed just before his death. It represents the first certain known attempt to apply a pendulum to control the rate of a clock. The application of the pendulum to clock timekeeping during the 17th century scientific revolution was one of the most fundamental advances in the history of time measurement.