<P> 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 centre 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 . </P> <P> Jewel bearings, introduced in England in 1702 by the Swiss mathematician 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". </P> <P> At Vacheron Constantin, Geneva, Georges - Auguste Leschot (1800--1884), pioneered the field of interchangeability in clockmaking by the invention of various machine tools . In 1830 he designed an anchor escapement, which his student, Antoine Léchaud, later mass - produced . He also invented a pantograph, allowing some degree of standardisation and interchangeability of parts on watches fitted with the same calibre . </P> <P> The British had predominated in watch manufacture for much of the 17th and 18th centuries, but maintained a system of production that was geared towards high quality products for the elite . Although there was an attempt to modernise clock manufacture with mass production techniques and the application of duplicating tools and machinery by the British Watch Company in 1843, it was in the United States that this system took off . Aaron Lufkin Dennison started a factory in 1851 in Massachusetts that used interchangeable parts, and by 1861 was running a successful enterprise incorporated as the Waltham Watch Company . </P>

Who invented the first wristwatch in the world