French Slate Weather Station Mantel Clock

• 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.
• Malachite - Malachite is bright copper-green coloured stone with concentric layers which displays distinct contrasting veinings. It has been valued in the past for making or decorating small precious objects such as clocks, jewellery, dishes and so. In the Orient it was used for snuff bottles and in Russia and was favoured by the Faberge workshop. larger pieces were used for table tops.
  
  The principal source of supply was Russia but it is to be found in other regions such as Southern Africa, Mexico, Australia and France.
  
  Malachite glass is a manufactured material that was intended to resemble malachite, but often bears more resemblance to a veined coloured marble due to its lower gloss finish and lack of concentric layers. Malachite glass was manufactured by many glassworks in the 19th century including Loetz in Austria and others in Bohemia and Davidson's Greener's and Sowerby in north eastern England.
  
  It was particularly used for scent bottles, bowls, and small vases often decorated with nymphs.
  
  Malachite glass has been manufactured continuously since the late nineteenth century, most is unmarked and it is difficult to distinguish the age or manufacturer of most commercial pieces.
• 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.
• Movement - The technical name for the workings of a clock or watch, and does not include the dial or case.
• Date Aperture - A date aperture is a cut out section in the face of a watch or clock, displaying the day of the month.
• 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.

This item has been included into following indexes:

• clocks, material or decoration
  • marble or slate, black 345
  • slate 347
• clocks, type - weather station clocks 17