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Watches evolved from portable spring driven clocks, which first appeared in 15th century Europe. Portable timepieces were made possible by the invention of the mainspring. Although some sources erroneously credit Nuremberg clockmaker Peter Henlein (or Henle or Hele) with inventing the mainspring around 1511, many references to 'clocks without weights' and two surviving examples show that spring powered clocks appeared in the 15th century. Henlein was a well-known craftsman of early "clock-watches" (taschenuhr), ornamental timepieces worn as pendants which were the first timepieces to be worn on the body. He is often credited as the inventor of the watch, mostly because of a passage by Johann Cochläus in 1511:
Peter Hele, still a young man, fashions works which even the most learned mathematicians admire. He shapes many-wheeled clocks out of small bits of iron, which run and chime the hours without weights for forty hours, whether carried at the breast or in a handbag
and because he was popularized in a 19th century novel. However, other German clockmakers were creating miniature timepieces during this period, and there is no evidence Henlein was the first. Watches weren't widely worn in pockets until the 17th century.
One account of the origin of the word "watch" is that it came from the Old English word woecce which meant "watchman", because it was used by town watchmen to keep track of their shifts. Another says that the term came from 17th century sailors, who used the new mechanisms to time the length of their shipboard watches (duty shifts).
The first timepieces to be worn, made in the 16th century in the German cities of Nuremberg and Augsburg, were transitional in size between clocks and watches. These 'clock-watches' were fastened to clothing or worn on a chain around the neck. They were heavy drum shaped cylindrical brass boxes several inches in diameter, engraved and ornamented. They had only an hour hand. The face was not covered with glass, but usually had a hinged brass cover, often decoratively pierced with grillwork so the time could be read without opening. The movement was made of iron or steel and held together with tapered pins and wedges, until screws began to be used after 1550. Many of the movements included striking or alarm mechanisms. They usually had to be wound twice a day. The shape later evolved into a rounded form; these were later called Nuremberg eggs. Still later in the century there was a trend for unusually shaped watches, and clock-watches shaped like books, animals, fruit, stars, flowers, insects, crosses, and even skulls (Death's head watches) were made.
The reason for wearing these early clock-watches was not to tell the time. The accuracy of their verge and foliot movements was so poor, with errors of perhaps several hours per day, that they were practically useless. They were made as jewelry and novelties for the nobility, valued for their fine ornamentation, unusual shape, or intriguing mechanism, and accurate timekeeping was of very minor importance.
Styles changed in the 17th century and men began to wear watches in pockets instead of as pendants (the woman's watch remained a pendant into the 20th century). This is said to have occurred in 1675 when Charles II of England introduced waistcoats. To fit in pockets, their shape evolved into the typical pocketwatch shape, rounded and flattened with no sharp edges. Glass was used to cover the face beginning around 1610. Watch fobs began to be used, the name originating from the German word fuppe, a small pocket. The watch was wound and also set by opening the back and fitting a key to a square arbor, and turning it.
The timekeeping mechanism in these early pocketwatches was the same one used in clocks, invented in the 13th century; the verge escapement which drove a foliot, a dumbbell shaped bar with weights on the ends, to oscillate back and forth. However, the mainspring introduced a source of error not present in weight-powered clocks. The force provided by a spring is not constant, but decreases as the spring unwinds. The rate of all timekeeping mechanisms is affected by changes in their drive force, but the primitive verge and foliot mechanism was especially sensitive to these changes, so early watches slowed down during their running period as the mainspring ran down. This problem, called lack of isochronism, plagued mechanical watches throughout their history.
Efforts to improve the accuracy of watches prior to 1657 focused on evening out the steep torque curve of the mainspring. Two devices to do this had appeared in the first clock-watches: the stackfreed and the fusee. The stackfreed, a spring-loaded cam on the mainspring shaft, added a lot of friction and was abandoned after about a century. The fusee was a much more lasting idea. A curving conical pulley with a chain wrapped around it attached to the mainspring barrel, it changed the leverage as the spring unwound, equalizing the drive force. Fusees became standard in all watches, and were used until the early 19th century. The foliot was also gradually replaced with the balance wheel, which had a higher moment of inertia for its size, allowing better timekeeping.
A great leap forward in accuracy occurred in 1657 with the addition of the balance spring to the balance wheel, an invention disputed both at the time and ever since between Robert Hooke and Christiaan Huygens. Prior to this, the only force limiting the back and forth motion of the balance wheel under the force of the escapement was the wheel's inertia. This caused the wheel's period to be very sensitive to the force of the mainspring. The balance spring made the balance wheel a harmonic oscillator, with a natural 'beat' resistant to disturbances. This increased watches' accuracy enormously, reducing error from perhaps several hours per day to perhaps 10 minutes per day, resulting in the addition of the minute hand to the face from around 1680 in Britain and 1700 in France. The increased accuracy of the balance wheel focused attention on errors caused by other parts of the movement, igniting a two century wave of watchmaking innovation. The first thing to be improved was the escapement. The verge escapement was replaced in quality watches by the cylinder escapement, invented by Thomas Tompion in 1695 and further developed by George Graham in the 1720s. In Britain a few quality watches went to the duplex escapement, invented by Jean Baptiste Dutertre in 1724. The advantage of these escapements was that they only gave the balance wheel a short push in the middle of its swing, leaving it 'detached' from the escapement to swing back and forth undisturbed during most of its cycle.
During the same period, improvements in manufacturing such as the tooth-cutting machine devised by Robert Hooke allowed some increase in the volume of watch production, although finishing and assembling was still done by hand until well into the 19th century.
The Enlightenment view of watches as scientific instruments brought rapid advances to their mechanisms. The development during this period of accurate marine chronometers to determine longitude during sea voyages produced many technological advances that were later used in watches. It was found that a major cause of error in balance wheel timepieces was changes in elasticity of the balance spring with temperature changes. This problem was solved by the bimetallic temperature compensated balance wheel invented in 1765 by Pierre Le Roy and improved by Thomas Earnshaw. This type of balance wheel had two semicircular arms made of a bimetallic construction. If the temperature rose, the arms bent inward slightly, causing the balance wheel to rotate faster back and forth, compensating for the slowing due to the weaker balance spring. This system, which could reduce temperature induced error to a few seconds per day, gradually began to be used in watches over the next hundred years.
The going barrel invented in 1760 by Jean-Antoine Lépine provided a more constant drive force over the watch's running period, and its adoption in the 19th century made the fusee obsolete. Complicated pocket chronometers and astronomical watches with many hands and functions were made during this period.
The lever escapement, invented by Thomas Mudge in 1759 and improved by Josiah Emery in 1785, gradually came into use from about 1800 onwards, chiefly in Britain; it was also adopted by Abraham-Louis Breguet, but Swiss watchmakers (who by now were the chief suppliers of watches to most of Europe) mostly adhered to the cylinder until the 1860s. By about 1900, however, the lever was used in almost every watch made. In this escapement the escape wheel pushed on a T shaped 'lever', which was unlocked as the balance wheel swung through its center position and gave the wheel a brief push before releasing it. The advantages of the lever was that it allowed the balance wheel to swing completely free during most of its cycle; due to 'locking' and 'draw' its action was very precise; and it was self-starting, so if the balance wheel was stopped by a jar it would start again. Jewel bearings, introduced in 1702 by Nicolas Fatio de Duillier, also came into use for quality watches during this period. Watches of this period are characterised by their thinness. New innovations, such as the cylinder and lever escapements, allowed watches to become much thinner than they had previously been. This caused a change in style. The thick pocketwatches based on the verge movement went out of fashion and were only worn by the poor, and were derisively referred to as "onions" and "turnips".
At Vacheron Constantin, Geneva, Georges-Auguste Leschot (1800–1884), pioneered in the field of interchangeability in clockmaking by the invention of various machine tools. 1830 he designed an anchor escapement, which his student, Antoine Léchaud, later mass produced. 1839 he invented a pantograph allowing some degree of standardisation and interchangeability of parts on watches fitted with the same calibre.
Watch manufacturing really changed from assembly in watchmaking shops to mass production with interchangeable parts, as from 1854, pioneered by the Waltham Watch Company, in Waltham, Massachusetts. The railroads' stringent requirements for accurate watches to safely schedule trains drove improvements in accuracy. The engineer Webb C. Ball, established around 1891 the first precision standards and a reliable timepiece inspection system for Railroad chronometers. Temperature compensated balance wheels began to be widely used in watches during this period, and jewel bearings became almost universal. Techniques for adjusting the balance spring for isochronism and positional errors discovered by Abraham-Louis Breguet, M. Phillips, and L. Lossier were adopted. The first international watch precision contest took place in 1876, during the International Centennial Exposition in Philadelphia (the winning four top watches, which outclassed all competitors, had been randomly selected out of the mass production line), on display was also the first fully automatic screw making machine. By 1900, with these advances, the accuracy of quality watches, properly adjusted, topped out at a few seconds per day.
From about 1860, key winding was replaced by keyless winding, where the watch was wound by turning the crown. The pin pallet escapement, an inexpensive version of the lever escapement invented in 1876 by Georges Frederic Roskopf was used in cheap mass produced dollar watches, which allowed ordinary workers to own a watch for the first time; other cheap watches used a simplifed version of the duplex escapement, developed by Daniel Buck in the 1870s.
These improvements were mostly originated and applied in the United States, and as a result the American industry ousted that of Switzerland from its long-held position as worldwide leader in the low-to-middle-class market. The Swiss responded, towards the end of the century, by changing their emphasis from economy to quality.
During the 20th century, the mechanical design of the watch became standardized, and advances were made in better materials, tighter tolerances, and improved production methods. The bimetallic temperature compensated balance wheel was made obsolete by the discovery of low temperature coefficient alloys invar and elinvar. A balance wheel of invar with a spring of elinvar was almost unaffected by temperature changes, so it replaced the complicated temperature compensated balance. The discovery in 1903 of a process to produce artificial sapphire made jewelling cheap. Bridge construction superseded 3/4 plate construction.
Patek Philippe created the first wristwatch in 1868. In 1880, Constant Girard (Girard-Perregaux) developed a concept of wristwatches, made for German naval officers and ordered by Kaiser Wilhelm I of Germany. Two-thousand watches were produced, which represents the first important commercialization of wristwatches for men; wristwatches were mostly worn by women until the First World War.
In 1904, Brazilian aviator Alberto Santos-Dumont asked his friend Louis Cartier to come up with an alternative that would allow him to keep both hands on the controls while timing his performances during flight. Cartier and his master watchmaker Edmond Jaeger soon came up with the first prototype for a man's wristwatch called the Santos wristwatch. The Santos first went on sale in 1911, the date of Cartier's first production of wristwatches.
However, the pocketwatch remained the favorite style among men until the First World War. During the war, soldiers needed access to their watches while their hands were full. They were issued wristwatches, called "trench watches", which were made with pocketwatch movements, so they were large and bulky and had the crown at the 12 o'clock position like pocketwatches. After the war, pocketwatches went out of fashion, and by 1930, the ratio of wrist- to pocketwatches was 50 to 1. The first successful self-winding system was invented by John Harwood in 1923.
The first generation electric-powered watches came out during this period. These kept time with a balance wheel powered by a solenoid, or in a few advanced watches that foreshadowed the quartz watch, by a steel tuning fork vibrating at 360 Hz, powered by a solenoid driven by a transistor oscillator circuit. The hands were still moved mechanically by a wheel train. In mechanical watches the self winding mechanism, shockproof balance pivots, and break resistant 'white metal' mainsprings became standard. The jewel craze caused 'jewel inflation' and watches with up to 100 jewels were produced.
The introduction of the quartz watch in 1969 was a revolutionary improvement in watch technology. In place of a balance wheel which oscillated at 5 beats per second, it used a quartz crystal resonator which vibrated at 8,192 Hz, driven by a battery powered oscillator circuit. In place of a wheel train to add up the beats into seconds, minutes, and hours, it used digital counters. The higher Q factor of the resonator, along with quartz's low temperature coefficient, resulted in better accuracy than the best mechanical watches, while the elimination of all moving parts made the watch more shock-resistant and eliminated the need for periodic cleaning. The first digital electronic watch with an LED display was developed in 1970.
Accuracy increased with the frequency of the crystal used, but so did power consumption. So the first generation watches had low frequencies of a few kilohertz, limiting their accuracy. The power saving use of CMOS logic and LCD displays in the 2nd generation increased battery life and allowed the crystal frequency to be increased to 32,768 Hz resulting in accuracy of 5–10 seconds per month. By the 1980s, quartz watches had taken over most of the watch market from the mechanical watch industry.
In 1990, Junghans offered the first radio-controlled wristwatch, the MEGA 1. In this type, the watch's quartz oscillator is set to the correct time daily by coded radio time signals broadcast by government-operated time stations such as WWVH, received by a radio receiver in the watch. This allows the watch to have the same long-term accuracy as the atomic clocks which control the time signals. Recent models are capable of receiving synchronization signals from various time stations worldwide.