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拍品专文
The present chronometer is noteworthy not only for its rarity but also because it employs a quick train movement (the balance beats 130 times a minute, 10 more than on a standard chronometer). Earnshaw is thought to be the first maker to use the quick train and did so on all his chronometers. Fewer than ten Earnshaw chronometers are known, the lowest serial number being 509/2853, in the British Museum.
By using a Vernier technique, comparing the beats of a standard regulator with those of his quick train, Earnshaw was able quickly to adjust his chronometers to their optimal rate, a process that would have normally taken days if not weeks. This was based on his balance vibrating at 130 beats per minute where its tick will only arrive exactly on a second stroke of a regulator every six seconds. By ascertaining which beat coincided with the tick of the regulator he was able to determine the error of the chronometer very precisely and adjust it accordingly (see J. A. Neale's account of Jonathan Betts' lecture, 'The Life and Work of Thomas Earnshaw', Antiquarian Horology, Spring 1998, vol. 24, pp. 55-57).
Thomas Earnshaw (1749-1829) was born in Ashton-under-Lyne, Lancashire. His company is recorded at 119 High Holborn, 1794-1795 and then 87 Fenchurch Street, 1795-1842. He is considered to be the father of the modern marine chronometer, inventing the spring detent escapement and the fused metal compensation balance, two innovations utilised by all the major chronometer makers and still in use today. Between 1791 and 1798 he submitted seven timepieces to the Board of Longitude and received a total of £3,000 of the £10,000 offered. Thomas Mudge and John Arnold both received the same amount, a division that Earnshaw strongly contested, prompting him to write a 314 page justification titled 'Longitude: An Appeal to the Public', where he detailed the development of his escapement.
By using a Vernier technique, comparing the beats of a standard regulator with those of his quick train, Earnshaw was able quickly to adjust his chronometers to their optimal rate, a process that would have normally taken days if not weeks. This was based on his balance vibrating at 130 beats per minute where its tick will only arrive exactly on a second stroke of a regulator every six seconds. By ascertaining which beat coincided with the tick of the regulator he was able to determine the error of the chronometer very precisely and adjust it accordingly (see J. A. Neale's account of Jonathan Betts' lecture, 'The Life and Work of Thomas Earnshaw', Antiquarian Horology, Spring 1998, vol. 24, pp. 55-57).
Thomas Earnshaw (1749-1829) was born in Ashton-under-Lyne, Lancashire. His company is recorded at 119 High Holborn, 1794-1795 and then 87 Fenchurch Street, 1795-1842. He is considered to be the father of the modern marine chronometer, inventing the spring detent escapement and the fused metal compensation balance, two innovations utilised by all the major chronometer makers and still in use today. Between 1791 and 1798 he submitted seven timepieces to the Board of Longitude and received a total of £3,000 of the £10,000 offered. Thomas Mudge and John Arnold both received the same amount, a division that Earnshaw strongly contested, prompting him to write a 314 page justification titled 'Longitude: An Appeal to the Public', where he detailed the development of his escapement.