Mantel clock, c.1925

In depth

This mantel clock was manufactured by Bulle, established in 1920, in France, by Maurice Favre-Bulle. Along with their rivals, ATO, Bulle made major innovations in battery technology at a time when domestic mains power was still unreliable, producing covetable clocks for domestic markets in a range of designs. The principle is an electromagnetic solenoid used as a pendulum bob, which swings back and forth over a stationary, curved magnetic bar. Near the top of the pendulum is a silver pin, which makes contact alternately with the two sides of a pivoted fork as the pendulum swings back and forth. One arm of the fork is insulated while the other acts as a conductor, allowing the circuit to be made and current to flow to the drive coil of the bob. An isochronal spring is fitted to the pendulum rod to attempt to correct for circular error. A skeletonised dial makes it possible to see Bulle’s distinctive ‘walking pawl’ escapement in action, which is activated by the side-to-side motion of the fork. The movement is mounted on a single brass column, which would originally have held the single cell battery required to power the clock. It is protected by a dome. The design is early, and appears in a Bulle catalogue of 1925.