- Thomas Earnshaw
name = Thomas Earnshaw
image_size = 160px
birth_date = birth date|1749|2|4|df=y
death_date = death date and age|1829|3|1|1749|2|4|df=y
occupation = Watchmaker
Thomas Earnshaw (born
4 February 1749in Ashton-under-Lyne- died 1 March 1829in London) was an English watchmakerwho first simplified the process of marine chronometerproduction, making them available to the general public. He's also known for his improvements to the transit clockat the Royal Greenwich Observatoryin London and his invention of the chronometer escapementand the bimetallic compensation balance. [http://www.britannica.com/eb/article-9031721 Thomas Earnshaw] at Encyclopaedia Britannica Online.]
In 1783 he invented and patented the spring detent
escapementwhich became standard in marine chronometers [http://www.antique-watch.com/ref/e_earn.html Details on Earnshaw's spring indent escapement] ] ( John Arnoldinvented a similar escapement in 1779). In 1805, Earnshaw and Arnold were granted awards by the Board of Longitudefor their improvements to chronometers; Earnshaw received £2500 and John Arnold's son John Roger Arnold received £1672. The bimetallic compensation balance and the spring detent escapement in the forms designed by Earnshaw have been used essentially universally in marine chronometers since then, and for this reason Earnshaw is generally regarded as the "father of the chronometer". [cite book | author=Gould, Rupert T. | title=The Marine Chronometer. Its History and Development | pages=116-128 | location=London | publisher=J. D. Potter | year=1923 | id=ISBN 0-907462-05-7]
Although, he was principly a watchmaker, he didn't shy away from building clocks. When asked by
Nevil Maskelyne, he produced a clock for the Armagh Observatory, which is recognised by horologists today as one of the world's most important clocks.Fact|date=February 2007
This clock incorporated Earnshaw's new design of escapement and had a number of novel features including an air-tight case (designed to reduce dust and draughts). It was highly praised by
John Thomas Romney Robinsonin the 19th century who at that time believed it to be the most accurate clock in the world. In 1794, its purchase price was £100 and Earnshaw charged £100 to travel with it to Armagh and set it up in the new Observatory. Information on [http://star.arm.ac.uk/history/instruments/Earnshaw-transit-clock.html Earnshaw's first clock] at the Armagh Observatory website.]
The Observatory also purchased Earnshaw's second clock Information on [http://www.arm.ac.uk/history/instruments/Earnshaw-clock.html Earnshaw's second clock] at the Armagh Observatory website.] which was operated at sidereal rate with Edward Troughton's Equatorial Telescope.
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