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A Quick Glossary of Horological Terms:


Anchor escapement - Often found in late seventeenth- and eighteenth-century clocks with long pendulums, the device consists of a flat, toothed wheel mounted at the end of the going train of a clock and a separate, semicircular piece of steel with pallets at each end of the semicircle that somewhat resembles a sea anchor. The anchor escapement engages with the pendulum by means of a short rod, or crutch, attached to the arbor of the anchor at one end and ending terminating on the other in a fork or slot that clasps the pendulum rod or a pin that fits within a slot in the pendulum rod. When in motion, the anchor rocks to and fro, releasing one tooth of the wheel and catching another, thus releasing the energy of the going train at small intervals, usually of one second in a longcase clock.

Chronometer - In modern usage, a timekeeper of great precision.

Contrate wheel - A wheel in which the teeth stand up at right angles to the plane of the wheel.

Equation clock - A clock that is made to display true solar time, the time measured by a sundial, which is governed by the diurnal revolutions of the earth in relation to the sun. Usually, such clocks also display mean solar time, or mean time, which is an average drawn from the length of all the solar days in the year and results in a day of exactly twenty-four equal hours. The difference between the two reaches a maximum of a little more than sixteen minutes.

Escapement - The mechanism that converts the continuous motion of the series of wheels, or going train, of a clock to the back-and-forth motion of its regulator.

Gilding - It can be done with gold leaf or with ormolu, or powdered gold. The latter was used for bronzes. The chaser-gilder ground the gold down to a fine powder on a milling stone, then blended it with mercury. The mixture was then heated until a paste was obtained. The paste was applied to the bronze with a brush, the piece was heated over an open flame, and as the mercury evaporated, the gold adhered to the bronze.

Going train - The series of toothed wheels that connect with a power source and drive the timekeeping mechanism, as well as and the hands, of a clock.

Gridiron pendulum - A pendulum consisting of multiple rods made of two metals (often brass and steel) with differing coefficients of expansion, that are arranged so that the total length of the pendulum remains constant and unaffected by changes in temperature.

Jacob Petit porcelain - Jacob Petit (1796-1868) owned one of the most important and well-known porcelain factories in France, becoming one of the major producers of Rococo ornamental ware during the 1830s. Between 1830 and 1850, new manufacturing techniques evolved that modernized the production process without sacrificing the craftsmanship of this time-honored trade.

Moon phase dial - Stylized dial that shows the current phase of the moon through a curved aperture in the calendar face.

Niderviller porcelain - In the mid-1700s, porcelain became so popular among the nobility that aristocrats began sponsoring their own manufactories. Jean-Louis Beyerlé, an advisor to the king, founded one such operation at Niderviller in 1748, developing it out of an earlier faience-making business. The new enterprise initially drew its workers and stylistic inspiration from a neighboring concern in Strasbourg, which produced ceramic wares in the Rococo taste. At Niderviller, the workers modified the bright Strasbourg palette, making it softer.

Pendules Pyramidales - The name, which appears in the Breguet registers, refers to two types of clock: one which is triangular, and another which features two bronze figures.

Perpetual calendar - A calendar complication that adjusts automatically to account for different lengths of the month (30 or 31 days) and leap years.

Regulator - A stationary clock of great precision. It usually has a seconds-beating, compensated pendulum, whether of the gridiron variety or some other variety, such as the mercury-filled jar, that adjusts to changes in temperature that would otherwise affect the length of the pendulum. Some have specially designed escapements, as well.

Remontoire - The remontoire provides a more constant and gentle power to the escapement. It consists of an endless chain passing over two toothed pulleys on the movement and supporting two weights suspended on grooved pulleys.

Silk suspension - The pendulum is suspended by silk thread that is wrapped around a shaft that has a knob on the end. When the knob is turned the pendulum is lengthened or shortened which adjusts the clock faster or slower.

Striking train - The series of toothed wheels that connect a power source with a hammer that strikes a bell (usually in seventeenth- and eighteenth-century clocks) and measures out the number of strikes required.

Verge escapement - A toothed wheel that is the last wheel in the going train of a clock across which is placed an arbor, or balance staff, with two pallets, or flags, attached to it in such a way that when the wheel revolves, the teeth of the wheel alternately engage a pallet, releasing the energy of the going train in short, measured intervals. It is the oldest practical form of escapement and can be used with circular balances as well as short pendulums.

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