“Perpetual motion” clock
Attributed to the Spoleto watchmaker and optician Giuseppe Campani (1635-1715), active in Rome in the second half of the 17th century, this instrument, despite its name, doesn’t produce any perpetual motion. The wooden case placed in the lower part of the instrument contains a clockwork mechanism powered by a weight. Instead of being entrusted to a pendulum or other type of escapement, the clock’s adjustment depends on the descent of a metal ball along a curved track inserted into a small loggia with eight columns. The ball runs along the track, enters the clockwork mechanism and triggers the hand, which moves forward. The ball then falls into the launch tube, releases a spring mechanism and is thrown upwards. It passes through a hole, descends along a short inclined plane in the upper part of the case and returns to its starting point. As the ball completes its 30-second descent cycle, the clockwork movement recharges the launch device.
The instrument has belonged to the collections of the family of the Medici Grand Dukes at least since 1692. As an inscription on the inside of the case testifies, it was completely refurbished in 1797 by cabinetmaker Pasquale Bassetti and mechanic Felice Gori.