The period of a circular pendulum is constant only when its oscillations are very small. If the amplitude of the oscillations is increased, they cease to be isochronous, except when the amplitude is very small. Christiaan Huygens (1629-1695) discovered that, by forcing the pendulum to travel on a cycloidal path, its period remained constant regardless of the amplitude of the oscillations. Huygens used the cycloidal pendulum with excellent results as an escape for regulating clock motions. For this purpose, the pendulum must be suspended from a highly flexible elastic strip or lamina oscillating between two cycloid arcs, so that the pendulum will follow their profile in its motion. The oscillations of the pendulum will thus describe a cycloidal and perfectly isochronous path.