Enamel Pocket Watch with Mock Pendulum, 1710

• Circa - A Latin term meaning 'about', often used in the antique trade to give an approximate date for the piece, usually considered to be five years on either side of the circa year. Thus, circa 1900 means the piece was made about 1900, probably between 1895 and 1905. The expression is sometimes abbreviated to c.1900.
• 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.
• Pair Cased - A pair cased watch is one with a double case. The movement is encased, and for additional protection this is fitted into an outer case.
• Foliate - Decorated with leaves or leaf-like forms.
• Polychrome - Made or finished in many colours. For furniture, it is used to indicated a painted finish.
• Movement - The technical name for the workings of a clock or watch, and does not include the dial or case.
• Embossed / Repousse - Embossing, also known as repousse, is the technique of decorating metal with raised designs, by pressing or beating out the design from the reverse side of the object.It is the opposite of chasing, where the decoration is applied from the front. An embossed or repoussed object may have chasing applied to finish off the design.
• Date Aperture - A date aperture is a cut out section in the face of a watch or clock, displaying the day of the month.
• 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.

This item has been included into following indexes:

• pocket watches, case type
  • enamelled decoration 157
  • pair cased 156
• pocket watches, period - Georgian 258