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Thomas Mercer Chronometers is a British company specialising in the design and production of bespoke chronometers. ==History== The story begins with John Harrison, as documented in Dava Sobel's book ''Longitude'' and its British television adaptation. So far, ships had been navigating with accuracy only as reards the ship’s north-south position, using the North Star and/or the Southern Cross. Determining the east-west position of a ship and its destination was vital to the Admiralty’s, (and the Government’s), plans for further expansion and empire. It was also necessary to avoid the massive losses in time, money and human life that inaccurate navigation and shipwreck caused. Lack of solutions led to the government making an Act of Parliament in 1714 offering a prize of £20,000 (£3M today). There was a whole spectrum of ideas suggested, ranging from serious (Whitton and Diston’s light-houses) to silly (using wounded dogs to yelp at set intervals). Isaac Newton was among the judges and concluded that a watch/clock would have to overcome the following challenge: a watch to keep time exactly: but by reason of the motion of the ship, the variation in heat and cold, wet and dry, and the difference in gravity at different latitudes, such a watch had not yet been made.〔http://www-history.mcs.st-and.ac.uk/HistTopics/Longitude2.html〕 The competition winner was Harrison’s Sea Watch chronometer, in essence a super-accurate clock which functioned despite the rock and roll of the ship, and enabled a hitherto unimaginable level of navigational accuracy, driving Great Britain’s maritime empire to ever greater heights. Harrison received his official award only after repeated appeals and indeed the intervention of George III. Harrison made only four chronometers, but his work was carried on by others, and (generally London-based) chronometer houses sprang up, great names like John Arnold, Edward John Dent, Thomas Earnshaw, Charles Frodsham, Hamilton, and Robert Molyneux. They refined his work: detent, chain and fusee, grasshopper escapement, and other developments informed their creations. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thomas Mercer Chronometers」の詳細全文を読む スポンサード リンク
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