Click on a part of the clock to find out more.

Athanasius Kircher's Magnetic clock, from Kircher, Magnes, sive de arte Magnetica, Rome: Ludovico Grignani, 1641

The clock was operated by means of a trick:  the falling level of a water-clock, or "clepsydra", hidden in the base of the machine caused a cylinder to rotate slowly. A strong magnet fixed to the top of the cylinder caused a second magnet, situated inside the copper globe suspended at the centre of the glass sphere, to follow its rotation. A stationary fish points to the hour markings on the rotating copper globe to give the time. Kircher claims to have calibrated his device so that the cylinder would rotate once every twenty-four hours, although the water-clock would probably have required frequent refilling. Kircher's work makes no reference to Francis Line's earlier invention, but Kircher had received letters from his Jesuit correspondents informing him about the device prior to the publication of the Magnes. 

Kircher offers two alternative techniques for suspending the copper globe inside the glass sphere -- either it can be suspended by threads made from silk or from Aloes leaves, or it can be suspended at the junction of two immiscible liquids of different densities, having the same colour.