watch

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Watch, small, portable timepiece usually designed to be worn on the person. Other kinds of timepieces are generally referred to as clocks. At one time it was generally believed that the first watches were made in Nuremburg, Germany, c.1500. However, there is now evidence that watches may have appeared at an earlier date in Italy. Early watches were ornate, very heavy, and made in a variety of shapes, e.g., pears, skulls, and crosses; the faces were protected by metal latticework. Watch parts were made by hand until c.1850, when machine methods were introduced by watch manufacturers in the United States. The introduction of machine-made parts not only cut manufacturing costs but increased precision and facilitated repairs. To insure the accuracy of a watch over a long period, bearings made of jewels (usually synthetic sapphires or rubies) are utilized at points subject to heavy wear. The mechanical watch contains a mainspring to drive the watch's mechanism. Part of the mechanism includes a hairspring and an oscillating balance wheel to control the rate at which the mechanism moves. The mainspring is wound by the wearer when he turns a knob outside the watch's casing. The automatic, or self-winding, watch has a mainspring that is wound by an oscillating weight, contained in the watch, that is set into motion by the movements of the wearer. The stopwatch can be stopped or started at will by pressing a tiny button on its edge and is used for timing such events as races. The electric watch, which was introduced by the Hamilton Watch Company in 1957, also uses a hairspring and a balance wheel to regulate the rate at which its mechanism moves, but it has no mainspring. In recent years sophisticated electronic watches have been developed. One type uses the vibrations of an electrically driven tuning fork to determine the rate at which a small motor drives the hands. In another type a crystal oscillator provides a signal that regulates this motion. In the most common type a quartz crystal oscillator is joined to digital counting and digital display circuits, thus eliminating all moving parts. Quartz watches with digital displays now account for nearly half of all watch production, since they are inexpensive to produce but are accurate to within several seconds per month. Electric and electronic watches are powered by tiny long-lasting batteries. See chronometer.

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