French Japy Freres Mantle Clock with Ormolu and Alabaster Case

• Alabaster - Alabaster is soft natural stone used for statuary, with a similar appearance to marble, but easier to work with. As it is softer than marble, an item made from alabaster can be scratched with a metal object, and an alabaster item does not polish to a high surface gloss like marble.
  
  Alabaster objects can be semi-translucent. Alabaster occurs in a pure white form and also with veining from dirt. Colours vary from white through yellow and pink to brown. The veining is usually green or black but can be multicoloured.
  
  Being semi-translucent, alabaster is often used for the bowls of figural lamps, with the figure itself being either alabaster or marble.
• Movement - The technical name for the workings of a clock or watch, and does not include the dial or case.
• Ormolu - Ormolu was popular with French craftsmen in the 18th and 19th century for ornamental fittings for furniture, clocks and other decorative items. True ormolu is gilt bronze, that is bronze that has been coated with gold using a mercury amalgam. Due to the health risks associated with using mercury, this method of creating ormolu was discontinued in France in the 1830s. A substitute was developed consisting of about 75% copper and 25% zinc, however it was inferior to the bronze version. It was often lacquered to prevent it tarnishing.
• 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.

This item has been included into following indexes:

• clocks, type - figural 695
• Japy Freres / Japy & Cie (France) - clocks, maker or retailer 150