HOME

TheInfoList



OR:

Thomas Earnshaw (4 February 1749 in
Ashton-under-Lyne Ashton-under-Lyne is a market town in Tameside, Greater Manchester, England. The population was 45,198 at the 2011 census. Historically in Lancashire, it is on the north bank of the River Tame, in the foothills of the Pennines, east of Manche ...
– 1 March 1829 in
London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
) was an
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ...
watchmaker who, following John Arnold's earlier work, further simplified the process of
marine chronometer A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT), or in the mode ...
production, making them available to the general public. He is also known for his improvements to the transit
clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and ...
at the
Royal Greenwich Observatory The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in ...
in London and his invention of a chronometer
escapement An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy ...
and a form of bimetallic compensation balance.Thomas Earnshaw
at Encyclopædia Britannica Online.
In 1780, he devised a modification to the detached chronometer
escapement An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy ...
, the detent being mounted on a spring instead of on pivots. This spring detent escapement was patented by Thomas Wright (for whom he worked) in 1783. Whilst initially the design was crude and unsuccessful, with modifications it later became the standard form in marine chronometers,Details on Earnshaw's spring indent escapement
following the invention of the detent escapement by Pierre Le Roy in 1748. John Arnold also invented a similar escapement in 1782. In 1805, Earnshaw and Arnold were granted awards by the
Board of Longitude The Commissioners for the Discovery of the Longitude at Sea, or more popularly Board of Longitude, was a British government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding lon ...
for 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 chronometer A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT), or in the mode ...
s since then, and for this reason Earnshaw is generally regarded as one of the pioneers of chronometer development. Although he was principally a watchmaker, he did not shy away from building clocks. When asked by
Nevil Maskelyne Nevil Maskelyne (; 6 October 1732 – 9 February 1811) was the fifth British Astronomer Royal. He held the office from 1765 to 1811. He was the first person to scientifically measure the mass of the planet Earth. He created the ''British Nau ...
, he produced a clock for the Armagh Observatory. This clock incorporated Earnshaw's new design of escapement and had a number of novel features, including an airtight case (designed to reduce dust and draughts). It was highly praised by John Thomas Romney Robinson in 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 o
Earnshaw's first clock
at the Armagh Observatory website.
The Observatory also purchased Earnshaw's second clockInformation o

at the Armagh Observatory website.
which was operated at sidereal rate with Edward Troughton's
Equatorial Telescope An equatorial mount is a mount for instruments that compensates for Earth's rotation by having one rotational axis, the polar axis, parallel to the Earth's axis of rotation. This type of mount is used for astronomical telescopes and cameras. The ...
.


Chronometers on notable voyages

In July, 1791, Captain
William Bligh Vice-Admiral William Bligh (9 September 1754 – 7 December 1817) was an officer of the Royal Navy and a colonial administrator. The mutiny on the HMS ''Bounty'' occurred in 1789 when the ship was under his command; after being set adrift i ...
purchased on behalf of the
Admiralty Admiralty most often refers to: *Admiralty, Hong Kong *Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964 *The rank of admiral *Admiralty law Admiralty can also refer to: Buildings * Admiralty, Traf ...
Earnshaw's chronometer no. 1503 at a price of for an expedition he was to command in to transport
breadfruit Breadfruit (''Artocarpus altilis'') is a species of flowering tree in the mulberry and jackfruit family ( Moraceae) believed to be a domesticated descendant of '' Artocarpus camansi'' originating in New Guinea, the Maluku Islands, and the Phil ...
plants from
Tahiti Tahiti (; Tahitian ; ; previously also known as Otaheite) is the largest island of the Windward group of the Society Islands in French Polynesia. It is located in the central part of the Pacific Ocean and the nearest major landmass is Austra ...
to the
West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greate ...
. This was the second expedition that Bligh had undertaken with this mission. The first expedition was with HMS ''Bounty'' which had ended in the infamous
mutiny Mutiny is a revolt among a group of people (typically of a military, of a crew or of a crew of pirates) to oppose, change, or overthrow an organization to which they were previously loyal. The term is commonly used for a rebellion among memb ...
led by
Fletcher Christian Fletcher Christian (25 September 1764 – 20 September 1793) was master's mate on board HMS ''Bounty'' during Lieutenant William Bligh's voyage to Tahiti during 1787–1789 for breadfruit plants. In the mutiny on the ''Bounty'', Christian se ...
and from which Bligh returned to England only with the greatest of difficulties. The second expedition, however, was entirely successful. Around 1796 Earnshaw, who had temporarily lost interest in the Board of Longitude reward, was tempted back by the failure of Josiah Emery to win it. Earnshaw had a low opinion of Emery's chronometers and claimed that an already existing chronometer of his, no. 265, could outperform Emery's even though it had just returned from a voyage to the West Indies and had not been cleaned (dirty oil has an adverse effect on the going of a chronometer). Earnshaw was easily proved right in this and his chronometer had a good average rate over a 12-month trial. However, he failed to win any reward because the method of rating required that the rate of the piece in the first month be used as the baseline for the trial rather than the absolute timekeeping of the instrument. Ironically, this method had originally been proposed by Earnshaw's ally Maskelyne. In June 1801,
Matthew Flinders Captain Matthew Flinders (16 March 1774 – 19 July 1814) was a British navigator and cartographer who led the first inshore circumnavigation of mainland Australia, then called New Holland. He is also credited as being the first person to ut ...
' ship, HMS ''Investigator'', carried two boxed Timekeepers by Earnshaw E520 and E543, at a cost of 100 Guineas each. ''Investigator'' also carried two of Arnled's timekeepers on the first
circumnavigation Circumnavigation is the complete navigation around an entire island, continent, or astronomical body (e.g. a planet or moon). This article focuses on the circumnavigation of Earth. The first recorded circumnavigation of the Earth was the ...
and mapping of the coastline of
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
. The chronometer, E520, was mounted in a wooden box with gimbals to compensate for the motion of the ship. Flinders went to shore regularly to check the settings of the chronometers against the stars. The Earnshaw chronometer was the only one working at the end of the journey, causing Flinders to refer to it in his book ''
A Voyage to Terra Australis ''A Voyage to Terra Australis: Undertaken for the Purpose of Completing the Discovery of that Vast Country, and Prosecuted in the Years 1801, 1802, and 1803, in His Majesty's Ship the Investigator'' was a sea voyage journal written by English mari ...
'' as "this excellent timekeeper". Flinders was taken prisoner-of-war by the French in
Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label= Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It ...
. In 1805 Captain Aken, a fellow prisoner, was released and returned to England. Flinders gave him the chronometers to return to the Greenwich Observatory. By some unknown sequence of events, the Earnshaw 520 was sold to an Australian collector and in 1937 became the property of the Museum of Applied Arts and Sciences (
Powerhouse Museum The Powerhouse Museum is the major branch of the Museum of Applied Arts & Sciences (MAAS) in Sydney, the others being the historic Sydney Observatory at Observatory Hill, and the newer Museums Discovery Centre at Castle Hill. Although often de ...
) in
Sydney Sydney ( ) is the capital city of the state of New South Wales, and the most populous city in both Australia and Oceania. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about towards the Blue Mounta ...
. It was not until 1976 that it was identified as the chronometer of Flinders' historic journey. Between 1831 and 1836, chronometer no. 509 was carried on HMS ''Beagle'' on a voyage to circumnavigate the globe and establish, for the first time, a chain of points around the world of accurately-known longitude. The ship was commanded by Captain Robert FitzRoy, a future Vice-Admiral and founder of the Meteorological Office. This was only one of many chronometers carried by the ''Beagle'' since great accuracy was required for this task. This was also the voyage that carried
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
who was afterwards inspired to write his book about the theory of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
, ''
On the Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life''),The book's full original title was ''On the Origin of Species by Me ...
''. The chronometer is object 91 in the
BBC Radio 4 BBC Radio 4 is a British national radio station owned and operated by the BBC that replaced the BBC Home Service in 1967. It broadcasts a wide variety of spoken-word programmes, including news, drama, comedy, science and history from the BBC's ...
series '' A History of the World in 100 Objects''."Ship's chronometer from HMS ''Beagle''"
"Ship's chronometer from HMS Beagle"
/ref>


References

{{DEFAULTSORT:Earnshaw, Thomas 1749 births 1829 deaths English watchmakers (people) People from Ashton-under-Lyne British scientific instrument makers