Congreve Rolling Ball Clock
The clock is made of heavy solid brass and sits on a glass covered mahogany base. The time is shown on 3 separated porcelain dials – second, minute, and hour. The clock is driven by a double spring movement. A small steel ball rolls back and forth on the lower platform with a zigzag track. When the ball reaches the end of the track, it triggers a lever and the platform then tilts so that the steel ball starts to roll back down to the other end of the platform. It takes the steel ball roughly 12 seconds to roll from one side to the other. This type of ‘mystery’ clock was invented by Sir William Congreve in 1808.
Congreve appears to have been unaware that rolling ball clocks had been invented earlier by both Nicolas Grollier de Servière and Johann Sayller. Congreve’s version differed from Grollier’s rolling ball clock in that the ball travelled down a zig-zag rather than straight path. While Sayller’s version had also used a zig-zag path, it had utilized a number of balls and a fixed table rather than the single ball and tilting table employed by Congreve. The “Extreme Detached Escapement” (as Congreve referred to his escapement design) was patented in 1808. Congreve, who was not a clock maker, hired Gravel and Tolkien to produce the first working version, which he then presented to the Prince of Wales in 1808. This version was weight-driven, but the second design, which appears to have been constructed by John Moxon, was spring-driven. The second model is in the collection of Buckingham Palace.
Congreve clocks are unreliable timekeepers — the time taken for the ball to travel along the track varies greatly depending on the cleanliness of the track and ball, and since the plate is aligned horizontally, it is easy for dust to accumulate.
Dimensions: 18″ H x 10″ W x 16″ D