This 19th century model is based on a drawing by Galileo's (1564-1642) friend and biographer, Viviani, of an incomplete pendulum clock, which Galileo designed just before his death. It represents the first known attempt to apply a pendulum to control the rate of a clock. Galileo had noticed that the pendulum's period of swing appeared to be independent of the extent of the 'arc' of the swing and recognised its potential for timekeeping, but died before his work could be completed. It was Huygens (1629-1693) in the Hague, Holland, who eventually built the first successful pendulum clock in 1656. The application of the pendulum to clock timekeeping during the scientific revolution of the 17th century was arguably the most fundamental advance in the history of time measurement.