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French perpetual calendar clock - Details:
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French perpetual calendar clock circa 1850. The 14 day movement strikes the hours and half hours on a bell with a Brocot dead beat escapement visible through the upper dial and a compensated pendulum of brass and steel peculiar to Ellicott's design.

The gilt engraved dial mask; the upper white enamel dial with blue steel 'Breguet' style hands and Roman chapter ring; the lower perpetual calendar showing: day, date, month, equation of time, and moon phase.

The numbers on the calendar dial around the inner circle indicate the difference between solar and mean time, which shows the 'equation of time'. This allowed people to set their clocks by using their sundials.

The movement signed 'Cromey, Bristol' and numbered 31945. The calendar movement numbered 31756. The case is glazed on three sides and open to the front; multi-colored gold ormolu on a white marble base; surmounted by a 'ruffled pigeon'; numbered 39703.

William Cromey is listed in Britten’s as a clockmaker and jeweler in Bristol, 1842.

Circa: 1850

Dimensions: Height 18" - width 10" at base

French perpetual calendar clock circa 1850.In 1752 British clockmaker John Ellicott developed a temperature compensated pendulum which was used by French clockmakers. The central rod is made of iron while the two peripheral rods are made of brass, which has a higher thermal expansion.

With a rise in temperature, the two brass rods expand more and press down on the levers which press up on the pins attached to the bob, raising the bob. This compensates for the lengthening of the central rod, keeping the bob at the same distance from the pendulum pivot. Therefore the pendulum's period of swing stays constant with changes in temperature.

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