Jewelry Information > Watches and Clocks
Watches and ClocksClocks and Watches - devices used to measure or indicate the passage of time. A clock, which is larger than a watch, is usually intended to be kept in one place; a watch is designed to be carried or worn. Both types of timepieces require a source of power and a means of transmitting and controlling it, as well as indicators to register the lapse of time units.
Throughout history, time has been measured by the movement of the earth relative to the sun and stars. The earliest type of timekeeper, dating from as far back as 3500BC, was the shadow clock, or gnomon, a vertical stick or obelisk that casts a shadow. An Egyptian shadow clock of the 8th century BC is still in existence.
The Mechanical Clock The historical origin of the mechanical clock is obscure. The first recorded examples are found in the 14th century. Until that time, a time-measuring instrument was known as a horologium, or hour teller.The name clock, which originally meant "bell," was first applied in the present sense to the huge, mechanical time indicators installed in bell towers in the late Middle Ages.
The Pendulum A series of inventions in the 17th and 18th centuries increased the accuracy of clockworks and reduced the weight and bulk of the mechanisms. Galileo had described late in the 16th century the property of a pendulum, known as isochronism, stating that the period of the swing is constant. In 1657 Dutch physicist Christiaan Huygens showed how a pendulum could be used to regulate a clock. Ten years later English physicist Robert Hooke invented an escapement, which permitted the use in clocks of a pendulum with a small arc of oscillation. British clockmaker George Graham improved the escapement, and John Harrison developed a means of compensating for variations in the length of a pendulum resulting from changes in temperature.
Watches Watchworks were developed when coiled springs were introduced as a source of power. This type of spring was used in Italy about 1450. About 1500 Peter Henlein, a locksmith in Nürnberg, Germany, began producing portable timepieces known popularly as Nürnberg eggs. In 1525 another artisan, Jacob Zech of Prague, invented a fusee, or spiral pulley, to equalize the uneven pull of the spring. Other improvements that increased the accuracy of watches included a spiral hairspring, invented about 1660 by Robert Hooke, for the balance wheel, and a lever escapement devised by British inventor Thomas Mudge about 1765.
Minute and second hands, and crystals to protect both the dial and hands, first appeared on 17th-century watches. Jeweled bearings to reduce friction and prolong the life of watchworks were introduced in the 18th century.
Movements - a watch's movement is the internal operating mechanism of a time piece. Today, most watches are battery operated and their movements are called quartz movements. A small battery activates a tiny quartz crystal whose rapid vibrations are changed by a microcomputer chip into energy to run the watch.
The old hand-wound watches all people used to wear featured mechanical movements. Mechanicals are driven by a mainspring connected to gears and a balance wheel. The stem you wind on a mechanical watch activates the mainspring, which then starts the watch without need of a battery. Watch connoisseurs today still delight in the intricacies of mechanical movements and some of the most expensive watches in the world continue to feature them.
Analogs - An analog watch features the old fashioned face we know best the one with the hour and minute hands. Digital watches are the other kind; they feature numerals printed out on a display panel.
Chronographs - A chronograph is essentially a watch that features stopwatch functions (that means it has a timer you can start and stop) and it is one of the most popular timepieces on the market. Watches that are called chronographs also perform normal timekeeping tasks, but they can do much more, Some chronos simply feature a hand that measures seconds. Others are more complex and can time longer or shorter periods or elapsed time. Chronographs can also determine speed or distance or time more than one event simultaneously. As writer and humorist Mark Twain once said while marveling about his watch: "It knows considerable more than the average voter." He might have been referring to today's chronographs.
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