English Oak Longcase Clock by John Walker, Newcastle

• 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.
• Oak - Native to Europe and England, oak has been used for joinery, furniture and building since the beginning of the medieval civilisation. It is a pale yellow in colour when freshly cut and darkens with age to a mid brown colour.
  
  Oak as a furniture timber was superceded by walnut in the 17th century, and in the 18th century by mahogany,
  
  Semi-fossilised bog oak is black in colour, and is found in peat bogs where the trees have fallen and been preserved from decay by the bog. It is used for jewellery and small carved trinkets.
  
  Pollard oak is taken from an oak that has been regularly pollarded, that is the upper branches have been removed at the top of the trunk, result that new branches would appear, and over time the top would become ball-like. . When harvested and sawn, the timber displays a continuous surface of knotty circles. The timber was scarce and expensive and was used in more expensive pieces of furniture in the Regency and Victorian periods.
• Date Aperture - A date aperture is a cut out section in the face of a watch or clock, displaying the day of the month.
• Spandrel - An architectural term that in horology refers to the triangular ornamental decoration in the corners of of the dial plate. The spandrels are usually of cast brass and may be additonally chased and engraved. On painted dial clocks the spandrels are also usually painted.

This item has been included into following indexes:

• clocks, grandfather / longcase, period or age - 18th century, other 107
• clocks, grandfather / longcase, type - other 181