Gustav Becker 400 Day Clock with Glass Dome

• 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.
• A/f, as Inspected - The letters "A/F" or "as inspected" as part of a description is the cataloguer's shorthand for "all faults" or "as found", meaning the item has some type of damage or deficiency, it is of uncertain date or provenance, and/or that the seller takes no responsibility for the completeness of the item or the accuracy of the description.

This item has been included into following indexes:

• clocks, type
  • 400 day 73
  • under glass dome 187
• Gustav Becker Clock Company (Germany) - clocks, makers or retailers 46
• meat covers / food covers / dish covers - pewter 1,562