Thomas Earnshaw
Encyclopedia
Thomas Earnshaw was an English
watchmaker
who following John Arnold
's earlier work, further simplified the process of marine chronometer
production, making them available to the general public. He is also known for his improvements to the transit clock
at the Royal Greenwich Observatory in London and his invention of a chronometer escapement
and a form of bimetallic compensation balance.
In 1780, he devised a modification to the detached chronometer escapement
, 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, 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
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
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 didn't shy away from building clocks. When asked by Nevil Maskelyne
, 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 air-tight 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.
The Observatory also purchased Earnshaw's second clock which was operated at sidereal
rate with Edward Troughton's
Equatorial Telescope
.
purchased on behalf of the Admiralty
Earnshaw's chronometer no. 1503 at a price of for an expedition he was to command in to transport breadfruit
plants from Tahiti
to the West Indies. 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
led by Fletcher Christian
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
' 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
and mapping of the coastline of Australia
. The chronometer, E520, is 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
as "this excellent timekeeper". Flinders was taken prisoner-of-war by the French in Mauritius
. 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 Earnshaw 520 was sold to an Australian collector and in 1937 became the property of the Museum of Applied Arts and Sciences (Powerhouse Museum
) in Sydney
. It was not until 1976 that it was identified as the chronometer of Flinders' historic journey.
Between 1831 and 1836 chronometer no. 506
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
who was afterwards inspired to write his book about the theory of evolution
, On the Origin of Species. The chronometer is object 91 in the BBC Radio 4
series A History of the World in 100 Objects
.
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
watchmaker
Watchmaker
A watchmaker is an artisan who makes and repairs watches. Since virtually all watches are now factory made, most modern watchmakers solely repair watches. However, originally they were master craftsmen who built watches, including all their parts, by hand...
who following John Arnold
John Arnold
John Arnold was an English watchmaker and inventor.John Arnold was the first to design a watch that was both practical and accurate, and also brought the term "Chronometer" in to use in its modern sense, meaning a precision timekeeper...
's earlier work, further simplified the process of marine chronometer
Marine chronometer
A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...
production, making them available to the general public. He is also known for his improvements to the transit clock
Clock
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...
at the Royal Greenwich Observatory in London and his invention of a chronometer escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
and a form of bimetallic compensation balance.
In 1780, he devised a modification to the detached chronometer escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
, 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, following the invention of the detent escapement by Pierre Le Roy
Pierre Le Roy
Pierre Le Roy was a French clockmaker. He was the inventor of the detent escapement, the temperature-compensated balance and the isochronous balance spring. His developments are considered as the foundation of the modern chronometer...
in 1748. John Arnold
John Arnold
John Arnold was an English watchmaker and inventor.John Arnold was the first to design a watch that was both practical and accurate, and also brought the term "Chronometer" in to use in its modern sense, meaning a precision timekeeper...
also invented a similar escapement in 1782.
In 1805, Earnshaw and Arnold were granted awards by the Board of Longitude
Board of Longitude
The Board of Longitude was the popular name for the Commissioners for the Discovery of the Longitude at Sea. It was a British Government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding longitude at sea.-Origins:Navigators and...
for their improvements to chronometers; Earnshaw received £
Pound sterling
The pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...
2500 and John Arnold's son John Roger Arnold received £
Pound sterling
The pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...
1672. The bimetallic compensation balance and the spring detent escapement in the forms designed by Earnshaw have been used essentially universally in marine chronometer
Marine chronometer
A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...
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 didn't shy away from building clocks. When asked by Nevil Maskelyne
Nevil Maskelyne
The Reverend Dr Nevil Maskelyne FRS was the fifth English Astronomer Royal. He held the office from 1765 to 1811.-Biography:...
, he produced a clock for the Armagh Observatory
Armagh Observatory
Armagh Observatory is a modern astronomical research institute with a rich heritage, based in Armagh, Northern Ireland. Around 25 astronomers are actively studying stellar astrophysics, the Sun, Solar System astronomy, and the Earth's climate....
. 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 Robinson
John Thomas Romney Robinson
Rev. Dr. Thomas Romney Robinson was an Irish astronomer and physicist. He was the longtime director of the Armagh Astronomical Observatory, one of the chief astronomical observatories in the U.K. during the 19th century....
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 £
Pound sterling
The pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...
100 and Earnshaw charged £
Pound sterling
The pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...
100 to travel with it to Armagh and set it up in the new Observatory.
The Observatory also purchased Earnshaw's second clock which was operated at sidereal
Sidereal time
Sidereal time is a time-keeping system astronomers use to keep track of the direction to point their telescopes to view a given star in the night sky...
rate with Edward Troughton's
Edward Troughton
Edward Troughton FRS was a British instrument maker who was notable for making telescopes and other astronomical instruments.Troughton was born at Corney, Cumberland...
Equatorial Telescope
Equatorial mount
An equatorial mount is a mount for instruments that follows the rotation of the sky by having one rotational axis parallel to the Earth's axis of rotation. This type of mount is used for astronomical telescopes and cameras...
.
Chronometers on notable voyages
In July, 1791, Captain William BlighWilliam Bligh
Vice Admiral William Bligh FRS RN was an officer of the British Royal Navy and a colonial administrator. A notorious mutiny occurred during his command of HMAV Bounty in 1789; Bligh and his loyal men made a remarkable voyage to Timor, after being set adrift in the Bounty's launch by the mutineers...
purchased on behalf of the Admiralty
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...
Earnshaw's chronometer no. 1503 at a price of for an expedition he was to command in to transport breadfruit
Breadfruit
Breadfruit is a species of flowering tree in the mulberry family, Moraceae, growing throughout Southeast Asia and most Pacific Ocean islands...
plants from Tahiti
Tahiti
Tahiti is the largest island in the Windward group of French Polynesia, located in the archipelago of the Society Islands in the southern Pacific Ocean. It is the economic, cultural and political centre of French Polynesia. The island was formed from volcanic activity and is high and mountainous...
to the West Indies. This was the second expedition that Bligh had undertaken with this mission. The first expedition was with HMS Bounty
HMS Bounty
HMS Bounty , famous as the scene of the Mutiny on the Bounty on 28 April 1789, was originally a three-masted cargo ship, the Bethia, purchased by the British Admiralty, then modified and commissioned as His Majesty's Armed Vessel the...
which had ended in the infamous mutiny
Mutiny on the Bounty
The mutiny on the Bounty was a mutiny that occurred aboard the British Royal Navy ship HMS Bounty on 28 April 1789, and has been commemorated by several books, films, and popular songs, many of which take considerable liberties with the facts. The mutiny was led by Fletcher Christian against the...
led by Fletcher Christian
Fletcher Christian
Fletcher Christian was a master's mate on board the Bounty during William Bligh's fateful voyage to Tahiti for breadfruit plants...
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
Matthew Flinders
Captain Matthew Flinders RN was one of the most successful navigators and cartographers of his age. In a career that spanned just over twenty years, he sailed with Captain William Bligh, circumnavigated Australia and encouraged the use of that name for the continent, which had previously been...
' ship, HMS Investigator
HMS Investigator
Nine ships of the Royal Navy have borne the name HMS Investigator. Another was planned, but renamed before being launched: was a 22-gun armed ship purchased in 1798 and taken into service as HMS Xenophon. She was renamed HMS Investigator in 1801 and used as a survey ship. Under the command of...
, 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
Circumnavigation – literally, "navigation of a circumference" – refers to travelling all the way around an island, a continent, or the entire planet Earth.- Global circumnavigation :...
and mapping of the coastline of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. The chronometer, E520, is 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
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 mariner and explorer Matthew Flinders...
as "this excellent timekeeper". Flinders was taken prisoner-of-war by the French in Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
. 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 Earnshaw 520 was sold to an Australian collector and in 1937 became the property of the Museum of Applied Arts and Sciences (Powerhouse Museum
Powerhouse Museum
The Powerhouse Museum is the major branch of the Museum of Applied Arts and Sciences in Sydney, the other being the historic Sydney Observatory...
) in Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...
. It was not until 1976 that it was identified as the chronometer of Flinders' historic journey.
Between 1831 and 1836 chronometer no. 506
Ship's chronometer from HMS Beagle
A Nautical chronometer made by Thomas Earnshaw , and once part of the equipment of HMS Beagle, the ship that carried Charles Darwin on his voyage around the world, is held in the British Museum...
was carried on HMS Beagle
HMS Beagle
HMS Beagle was a Cherokee-class 10-gun brig-sloop of the Royal Navy. She was launched on 11 May 1820 from the Woolwich Dockyard on the River Thames, at a cost of £7,803. In July of that year she took part in a fleet review celebrating the coronation of King George IV of the United Kingdom in which...
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
Robert FitzRoy
Vice-Admiral Robert FitzRoy RN achieved lasting fame as the captain of HMS Beagle during Charles Darwin's famous voyage, and as a pioneering meteorologist who made accurate weather forecasting a reality...
, 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 Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
who was afterwards inspired to write his book about the theory of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
, On the Origin of Species. The chronometer is object 91 in the BBC Radio 4
BBC Radio 4
BBC Radio 4 is a British domestic radio station, operated and owned by the BBC, that broadcasts a wide variety of spoken-word programmes, including news, drama, comedy, science and history. It replaced the BBC Home Service in 1967. The station controller is currently Gwyneth Williams, and the...
series A History of the World in 100 Objects
A History of the World in 100 Objects
A History of the World in 100 Objects was a joint project of BBC Radio 4 and the British Museum, comprising a 100-part radio series written and presented by British Museum director Neil MacGregor...
.