A black marble mantle clock, later 19th century, of plain architectural form having a black dial with Roman numerals set, within an elongated plinth of geometric shaped form with an extended cornice, and stepped base, restrained incised decoration picked out in gilt, with key, and pendulum, height 20 cm, width 41 cm, depth 16 cm
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- 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.
- Incised - A record of a name, date or inscription, or a decoration scratched into a surface, usually of a glass or ceramic item with a blunt instrument to make a coarse indentation. Compare with engraving where the surface is cut with a sharp instrument such as a metal needle or rotating tool to achieve a fine indentation.
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