Jaeger Lecoultre Atmos Moonphase Clock

• Moon Dial - If we imagine life in the 17th century, the only source of ascertaining the time of day or night would have been the local church or municipal clock striking every quarter hour, and able to be heard by all in the village. In England, when longcase clocks became popular and more affordable in the late 17th century, the function of timekeeping and source of time was moved to within the home.
  
  An additional feature on some longcase clocks was to display the phases of the moon, that is the new moon, the full moon and the waning moon over the lunar 29 ½ day cycle. This information was important for farmers for working out cropping schedules; for travellers to know the amount of moonlight on a night they planned to travel; and for those who lived near the sea required knowledge of the tides.
  
  Where included, the moon dial is usually in the form of a disc incorporated into the main dial plate, usually in the arched top section. The lunar cycle starts with the new moon displaying, which is a dark night sky and no man-in-the-moon face being displayed, and then progresses to the full moon face showing on the 15th day of the lunar cycle, and back to no face displaying as the moon wanes. Most lunar dials are partially concealed on each side of their opening in the main dial plate by semi-circular "humps" that allow the painted face to emerge slowly just as the real moon goes out of and back into the earth's shadow.
  
  Nowadays, details of the lunar cycle is published in diaries, almanacs, and newspapers and although some modern longcase clocks are still manufactured with working moon dials, they are more for decoration than for use.
• Movement - The technical name for the workings of a clock or watch, and does not include the dial or case.
• 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.
• Lever Escapement - A lever escapement is a type of escapement mechanism used in mechanical clocks and watches to regulate the timekeeping of the movement. It was invented by British clockmaker Thomas Mudge in the 18th century and is now widely used in modern mechanical timepieces.
  
  The lever escapement consists of three main parts: the escape wheel, the pallet fork, and the lever. The escape wheel is a wheel with teeth that is driven by the clock or watch's main spring or weight. The pallet fork is a two-pronged component that is positioned so that it can engage with the teeth of the escape wheel, and the lever is a small, L-shaped component that is attached to the pallet fork.
  
  When the escape wheel turns, one of its teeth pushes against one of the pallet fork's prongs, causing the fork to pivot. As the pallet fork pivots, it releases the tooth and engages with the next tooth on the opposite side of the escape wheel. At the same time, the lever, which is connected to the pallet fork, rocks back and forth, allowing the escape wheel to turn at a regulated rate.
  
  The lever escapement is prized for its accuracy and reliability and is commonly used in high-end mechanical watches. It allows for precise timekeeping by ensuring that the movement of the watch or clock is regulated and consistent, and its compact size makes it an ideal choice for use in small, portable timepieces.

This item has been included into following indexes:

• clocks, type - Atmos 74
• Jaeger LeCoultre (Switzerland) - clocks and watches, maker or retailer 73