Athanasius Kircher's magnetic clock
 

Francis Line's magnetic clock

A version of the device was constructed by an English Jesuit professor in Liège, Fr. Francis Line, and was described in the book De symbolis heroicis, published in 1634. The device consisted of a small solid orb, marked with the twelve hours and balanced “by a secret balancing of its mass” at the centre of a glass sphere filled with water. The orb was perceived to rotate “by an arcane force”, following the motions of the heavens from West to East. The time of day was indicated on the orb by a small fish, poised in the water.

The device immediately attracted the attention of learned figures throughout Europe, including Rubens and Kircher’s patron, Nicholas Claude Fabri de Peiresc. Peiresc was convinced that the mysterious motion of the orb, apparently caused by a cosmic magnetic influence, might, by analogy, provide a demonstration of the diurnal motion of the Earth, thus vindicating Copernicus and providing hope for a revocation of Galileo’s condemnation by the Inquisition in 1633. 

While Peiresc continued to hold out hope, the ageing Galileo, confined under house-arrest in his Villa in Arcetri near Florence, wrote a letter to Peiresc to suggest that the device was operated by means of a trick – a magnet hidden in the base, rotated by means of a clock, caused another magnet in the ball to rotate, giving rise to the effect.

In Kircher’s Magnes, the secret mechanism of the magnetic clock was fully revealed, and it was finally disarmed as a pro-Copernican argument. In addition to explaining the magnetic rotation of the sphere, which Kircher compared to the action of the Prime Mover in rotating the firmament, Kircher described how the ball could be made to “hover” at the centre of the glass globe by placing it at the junction of two immiscible liquids of different densities.

The story of Kircher’s magnetic clock thus brings together the playful nature of Baroque instrumentation and the major cosmological debates of the seventeenth century, situating Kircher’s experimental productions within a European network of scholars. artists and patrons, including Rubens, Peiresc and Galileo.