Brass Skeleton Clock with Fretwork Detail
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An old brass skeleton clock, fusee chain movement with vertically stacked gears and bob pendulum, fretwork cut brass frame with vine detail and chapter ring with Arabic numerals. Clock height 38.5 cm. On oval white marble stand. Provenance: Private Auckland Collection. See lot 181.
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- Movement - The technical name for the workings of a clock or watch, and does not include the dial or case.
- Bob Pendulum - A bob pendulum consists of a brass or steel rod with a disc shaped metal weight at the end. The most common use of a bob pendulum is in a grandfather clock where it oscillates to keep the time. The length of the rod and the weight of the bob are the key parameters for determining the period of oscillation, and the timekeeping of the clock can be accelerated or slowed by altering the height of the bob.
- Chapter Ring - A separate metal plate on the face of a clock, on which the numerals for the hours and sometimes parts of the hours, are displayed, usually wheel shaped and sitting on top of the dial plate. The chapter ring is often a feature of the clock and can be silvered or enamelled to stand as a contrast to its background. The hours are usually shown in Roman numerals, although in the late 19th and earlt 20th century, Arabic numerals became fashionable.
- Fusee - The fusee movement was used in clocks and pocket watches from the mid 17th century. The fusee is a cone shaped drum within the works that is linked to the barrel of the spring, usually by a length of chain.
As the mainspring loses its tension over time, the cone shaped barrel compensates for this by increasing the tension, by pulling the mainspring tighter, thus ensuring the time remains constant.
Use of the fusee in clocks was superseded by the "going barrel" in the mid 19th century and for pocket watches at the beginning of the 19th century.
The fusee continued to be used in marine chronometers until the 1970s. - Pendulum - The pendulum was discovered around 1602 by Galileo Galilei, and was adopted for time keeping by the Dutch mathematician and natural philosopher, Christiaan Huygens, who excelled in astronomy, physics, and horology.
The pendulum comprises a metal rod usually of brass or steel with a metal disk, known as a bob, at the end. The movement of the pendulum is driven by weights or a spring, and as a pendulum swings in a regular arc, it was found accuracy could be controlled to within a few seconds a week.
Timekeeping can be adjusted by changing the height of the bob on the rod, making the pendulum either swing slower or faster.
The disadvantage of the pendulum was that changes in temperature also changed the length of the pendulum, interfering with the accuracy of the clock, and so in the 18th century two types of mercurial pendulums were invented which countered the movement in the steel rod.
The pendulum was the world's most accurate timekeeping technology until the invention of the quartz clock, regulated by a quartz crystal, in 1927.
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