John Harrison

John Harrison

Overview
John Harrison was a self-educated English clockmaker
Clockmaker
A clockmaker is an artisan who makes and repairs clocks. Since almost all clocks are now factory-made, most modern clockmakers only repair clocks. Modern clockmakers may be employed by jewellers, antique shops, and places devoted strictly to repairing clocks and watches...

. He invented the 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...

, a long-sought device in solving the problem of establishing the East-West position or longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age of Sail
Age of Sail
The Age of Sail was the period in which international trade and naval warfare were dominated by sailing ships, lasting from the 16th to the mid 19th century...

. The problem was considered so intractable that the British Parliament offered a prize
Longitude prize
The Longitude Prize was a reward offered by the British government for a simple and practical method for the precise determination of a ship's longitude...

 of £20,000 (comparable to £ in modern currency) for the solution.

Harrison came 39th in the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

's 2002 public poll of the 100 Greatest Britons
100 Greatest Britons
100 Greatest Britons was broadcast in 2002 by the BBC. The programme was the result of a vote conducted to determine whom the United Kingdom public considers the greatest British people in history. The series, Great Britons, included individual programmes on the top ten, with viewers having further...

.

John Harrison was born in Foulby
Foulby
Foulby is a village in the county of West Yorkshire, England. It is situated near Nostell, between Crofton and Ackworth Moor Top, on the A638 east-south east of the city of Wakefield.-Persons:...

, near Wakefield
Wakefield
Wakefield is the main settlement and administrative centre of the City of Wakefield, a metropolitan district of West Yorkshire, England. Located by the River Calder on the eastern edge of the Pennines, the urban area is and had a population of 76,886 in 2001....

 in West Yorkshire, the first of five children in his family.
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Encyclopedia
John Harrison was a self-educated English clockmaker
Clockmaker
A clockmaker is an artisan who makes and repairs clocks. Since almost all clocks are now factory-made, most modern clockmakers only repair clocks. Modern clockmakers may be employed by jewellers, antique shops, and places devoted strictly to repairing clocks and watches...

. He invented the 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...

, a long-sought device in solving the problem of establishing the East-West position or longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age of Sail
Age of Sail
The Age of Sail was the period in which international trade and naval warfare were dominated by sailing ships, lasting from the 16th to the mid 19th century...

. The problem was considered so intractable that the British Parliament offered a prize
Longitude prize
The Longitude Prize was a reward offered by the British government for a simple and practical method for the precise determination of a ship's longitude...

 of £20,000 (comparable to £ in modern currency) for the solution.

Harrison came 39th in the BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

's 2002 public poll of the 100 Greatest Britons
100 Greatest Britons
100 Greatest Britons was broadcast in 2002 by the BBC. The programme was the result of a vote conducted to determine whom the United Kingdom public considers the greatest British people in history. The series, Great Britons, included individual programmes on the top ten, with viewers having further...

.

Early life


John Harrison was born in Foulby
Foulby
Foulby is a village in the county of West Yorkshire, England. It is situated near Nostell, between Crofton and Ackworth Moor Top, on the A638 east-south east of the city of Wakefield.-Persons:...

, near Wakefield
Wakefield
Wakefield is the main settlement and administrative centre of the City of Wakefield, a metropolitan district of West Yorkshire, England. Located by the River Calder on the eastern edge of the Pennines, the urban area is and had a population of 76,886 in 2001....

 in West Yorkshire, the first of five children in his family. His father worked as a carpenter at the nearby Nostell Priory
Nostell Priory
Nostell Priory is a Palladian house located in Nostell, near Crofton close to Wakefield, West Yorkshire, England, approached by the Doncaster road from Wakefield...

 estate. The house where he was born bears a blue plaque
Blue plaque
A blue plaque is a permanent sign installed in a public place to commemorate a link between that location and a famous person or event, serving as a historical marker....

.

Around 1700, the family moved to the North Lincolnshire
North Lincolnshire
North Lincolnshire is a unitary authority area in the region of Yorkshire and the Humber in England. For ceremonial purposes it is part of Lincolnshire....

 village of Barrow upon Humber
Barrow upon Humber
Barrow upon Humber is a village and civil parish in North Lincolnshire, England. Many of the buildings in the centre of the village are of 18th and 19th century origin. There are several buildings of note including Down Hall, Barrow Hall, Forester's Hall and West Cote Farm. There are two public...

. Following his father's trade as a carpenter
Carpentry
A carpenter is a skilled craftsperson who works with timber to construct, install and maintain buildings, furniture, and other objects. The work, known as carpentry, may involve manual labor and work outdoors....

, Harrison built and repaired clocks in his spare time. Legend has it that at the age of six while in bed with smallpox
Smallpox
Smallpox was an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning "spotted", or varus, meaning "pimple"...

 he was given a watch to amuse himself, spending hours listening to it and studying its moving parts.

He also had a fascination for music, eventually becoming choirmaster for Barrow parish church.

Career



Harrison built his first longcase clock
Longcase clock
A longcase clock, also tall-case clock, floor clock, or grandfather clock, is a tall, freestanding, weight-driven pendulum clock with the pendulum held inside the tower, or waist of the case. Clocks of this style are commonly 1.8–2.4 metres tall...

 in 1713, at the age of 20. The mechanism was made entirely of wood, which was a natural choice of material for a joiner. Three of Harrison's early wooden clocks have survived; the first (1713) is at the Worshipful Company of Clockmakers
Worshipful Company of Clockmakers
The Worshipful Company of Clockmakers is one of the Livery Companies of the City of London. The Clockmakers were formed by a Royal Charter in 1631. Originally, no person was allowed to sell clocks unless they were a member of the Company. However, such requirements have since been relaxed and later...

' Collection in Guildhall
Guildhall, London
The Guildhall is a building in the City of London, off Gresham and Basinghall streets, in the wards of Bassishaw and Cheap. It has been used as a town hall for several hundred years, and is still the ceremonial and administrative centre of the City of London and its Corporation...

; the second (1715), is in the Science Museum and the third (1717) is at Nostell Priory
Nostell Priory
Nostell Priory is a Palladian house located in Nostell, near Crofton close to Wakefield, West Yorkshire, England, approached by the Doncaster road from Wakefield...

 in Yorkshire, the face bearing the inscription "John Harrison Barrow". The Nostell example, in the billiards
Billiards
Cue sports , also known as billiard sports, are a wide variety of games of skill generally played with a cue stick which is used to strike billiard balls, moving them around a cloth-covered billiards table bounded by rubber .Historically, the umbrella term was billiards...

 room of this fine stately home, has a Victorian
Victorian decorative arts
Victorian decorative arts refers to the style of decorative arts during the Victorian era. The Victorian era is known for its eclectic revival and interpretation of historic styles and the introduction of cross-cultural influences from the middle east and Asia in furniture, fittings, and Interior...

 outer case, which has been thoughtfully provided with small glass windows on each side of the movement so that the wooden workings may be inspected. In the early 1720s Harrison was commissioned to make a new turret clock at Brocklesby Park
Brocklesby
Brocklesby is a village and civil parish in the West Lindsey district of Lincolnshire, England. The village is 1 mile south of Habrough, 4 miles southwest of Immingham, close to the border of both North Lincolnshire and North East Lincolnshire, and near Humberside International Airport...

, North Lincolnshire. The clock still operates and like his previous clocks has a wooden movement, made of oak and lignum vitae
Lignum vitae
Lignum vitae is a trade wood, also called guayacan or guaiacum, and in parts of Europe known as pockenholz, from trees of the genus Guaiacum. This wood was once very important for applications requiring a material with its extraordinary combination of strength, toughness and density...

. Unlike his early clocks it incorporates some original features to improve timekeeping, for example the grasshopper escapement
Grasshopper escapement
The grasshopper escapement is an unusual, low-friction escapement for pendulum clocks invented by British clockmaker John Harrison around 1722. An escapement, part of every mechanical clock, is the mechanism that causes the clock's gears to move forward by a fixed distance at regular intervals and...

. Between 1725 and 1728 John and his brother James, also a skilled joiner, made at least three precision pendulum-clocks, again with oak and lignum vitae movements and longcase. The grid-iron pendulum
Gridiron pendulum
The gridiron pendulum was an improved clock pendulum invented by British clockmaker John Harrison around 1726. It didn't change its effective length with temperature, so its period of swing stayed constant with changes in ambient temperature...

 was developed during this phase. These precision pendulum-clocks are thought by some to have been the most accurate clocks in the world at the time, and significantly are the direct link to the sea clocks. No.1, now in a private collection was in the collections of the Time Museum, USA, until that museum closed in 2000 and its collection dispersed at auction in 2004. No. 2 is in the collections of Leeds Museums and Galleries, West Yorkshire, United Kingdom. It is not on display but it is planned to put it on permanent display in the new Leeds City Museum some time in 2011. No. 3 is in the Worshipful Company of Clockmakers' collection.

He was a man of many skills and used these to systematically improve the performance of pendulum
Pendulum
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position...

 clocks. He invented the gridiron pendulum, consisting of alternating brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

 and iron rods assembled so that the different expansions and contractions cancel each other out. Another example of his inventive genius was the grasshopper escapement
Grasshopper escapement
The grasshopper escapement is an unusual, low-friction escapement for pendulum clocks invented by British clockmaker John Harrison around 1722. An escapement, part of every mechanical clock, is the mechanism that causes the clock's gears to move forward by a fixed distance at regular intervals and...

 – a control device for the step-by-step release of a clock's driving power. Developed from the anchor escapement, it was almost friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

less, requiring no lubrication
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...

 because the pallets were made from the wood lignum vitae. This was an important advantage at a time when lubricants and their degradation were little understood. It is not often recognized that in his earlier work on the "Sea clocks" Harrison was continually assisted both financially and in many other ways by George Graham
George Graham (clockmaker)
George Graham was an English clockmaker, inventor, and geophysicist, and a Fellow of the Royal Society.He was born to George Graham in Kirklinton, Cumberland. A Friend like his mentor Thomas Tompion, Graham left Cumberland in 1688 for London to work with Tompion...

, the watchmaker and instrument maker who lent him a large sum on the basis of trust even after Harrison's first visit to Graham in 1728 to explain how his timekeeper worked. Harrison was introduced to Graham by the Astronomer Royal
Astronomer Royal
Astronomer Royal is a senior post in the Royal Household of the Sovereign of the United Kingdom. There are two officers, the senior being the Astronomer Royal dating from 22 June 1675; the second is the Astronomer Royal for Scotland dating from 1834....

 Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...

 who also championed Harrison and his work. This support was important as Harrison is reputed to have found it difficult to communicate his ideas in a coherent manner.

Overview of the problem


A longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 describes the location of a place on Earth east or west of a north-south line called the Prime Meridian
Prime Meridian
The Prime Meridian is the meridian at which the longitude is defined to be 0°.The Prime Meridian and its opposite the 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.An international...

. Longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 is given as an angular measurement
Angle
In geometry, an angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle.Angles are usually presumed to be in a Euclidean plane with the circle taken for standard with regard to direction. In fact, an angle is frequently viewed as a measure of an circular arc...

 ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Many solutions were proposed for how to determine longitude at the end of an exploratory sea voyage and hence the longitude of the place that was visited (in case one would want to revisit or place it on a map
Map
A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....

). The practical methods relied on a comparison of local time with the time at a given place (such as Greenwich
Greenwich
Greenwich is a district of south London, England, located in the London Borough of Greenwich.Greenwich is best known for its maritime history and for giving its name to the Greenwich Meridian and Greenwich Mean Time...

 or Paris). Many of these methods relied on astronomical observations
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

 relying on the predictable, "clockwork" nature of motions of heavenly bodies.
Harrison instead set out to solve the problem in a direct way: by producing a reliable clock. The theory was simple and had been first proposed by Frisius
Gemma Frisius
Gemma Frisius , was a physician, mathematician, cartographer, philosopher, and instrument maker...

. The difficulty, however, was in producing a clock which could maintain accurate time on a lengthy, rough sea voyage with widely varying conditions of temperature, pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 and humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...

. Frisius had realized that to determine longitude, a clock would have to be “of great exactness”. Many leading scientists including Newton
Isaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...

 and Huygens doubted that such a clock could ever be built and had more optimism for astronomical observations (such as the Method of Lunar Distances). Huygens ran trials using both a pendulum
Pendulum
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position...

 and a spiral balance spring
Balance spring
A balance spring, or hairspring, is a part used in mechanical timepieces. The balance spring, attached to the balance wheel, controls the speed at which the wheels of the timepiece turn, and thus the rate of movement of the hands...

 clock as methods of determining longitude. Although both types showed some favourable results, they were both prone to fickleness. Newton observed that “A good watch may serve to keep a reckoning at sea for some days and to know the time of a celestial observation; and for this end a good Jewel may suffice till a better sought of watch can be found out. But when longitude at sea is lost, it cannot be found again by any watch.” However, if such a clock were built and set at noon in London at the start of a voyage, it would subsequently always tell you how far from noon it was in London at that second, regardless of where you had traveled. By referring to the clock when it is noon locally (i.e. the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 is at its highest in the sky where you are) you can read, almost directly from the clock face, how far around the world you are from London. For instance, if the clock shows that it is midnight in London when it is noon locally, then you are half way round the world, (e.g. 180 degrees of longitude) from London.

This is so because the earth is constantly rotating, and therefore knowing the time while making an altitude measurement to a known heavenly body such as the sun, provided critical data for a ship's position east-west—a necessary capability for re-approaching land after voyages over medium and long distances. On such voyages, cumulative errors in dead reckoning
Dead reckoning
In navigation, dead reckoning is the process of calculating one's current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course...

 frequently led to shipwrecks and lost lives. Avoiding maritime tragedies became an imperative in Harrison's lifetime because this was an era when trade and navigation were on an explosive increase around the globe due to the maturing of other technologies, and also due to geo-political circumstances.

Knowing such measurements without an accurate time could only show position in latitude which was a trivial problem in comparison. Such a maritime 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...

 had to be not only highly accurate over long time intervals, but relatively impervious to corrosion in salt air, able to tolerate wide variations in temperature and humidity and in general durable while able to function at the odd angles and pitch and yaw typical of decks under strong waves and storm tossed conditions.

Yet the timekeeping device with such accuracy would eventually also allow the determination of longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 accurately, making the device a fundamental key to the modern age. Following Harrison, the marine timekeeper was reinvented yet again by 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...

 who while basing his design on Harrison's most important principles, at the same time simplified it enough for him to produce equally accurate but far less costly 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 in quantity from around 1783. Nonetheless, for many years even towards the end of the 18th century, chronometers were expensive rarities, as their adoption and use proceeded slowly due to the precision manufacturing necessary and hence high expense. The expiry of Arnold's patents at the end of the 1790s enabled many other watchmakers including Thomas Earnshaw
Thomas Earnshaw
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...

 to produce chronometers in greater quantities at less cost even than those of Arnold's.
By the early 19th century, navigation at sea without one was considered unwise to unthinkable. Using a chronometer to aid navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

 simply saved lives and ships—the insurance industry, exercise of self-interest, and common sense did the rest in making the device a universal tool of maritime trade.

The first three marine timekeepers


The English clockmaker Henry Sully
Henry Sully
Henry Sully was an English clockmaker. He lived for many years in France.-Marine clock:He invented a marine clock to determine longitude accurately, a sophisticated pendulum clock. He presented a first Montre de la Mer in 1716 to the French Académie des Sciences. He was the first to develop...

 had already invented a marine clock
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...

 to determine longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 accurately, a sophisticated pendulum clock
Pendulum clock
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a resonant device; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates...

. He presented a first Montre de la Mer in 1716 to the French Académie des Sciences. and in 1726 published Une Horloge inventée et executée par M. Sulli.

In 1730 Harrison created a description and drawings for a proposed marine clock to compete for the Longitude Prize
Longitude prize
The Longitude Prize was a reward offered by the British government for a simple and practical method for the precise determination of a ship's longitude...

 and went to London seeking financial assistance. He presented his ideas to Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...

, the Astronomer Royal
Astronomer Royal
Astronomer Royal is a senior post in the Royal Household of the Sovereign of the United Kingdom. There are two officers, the senior being the Astronomer Royal dating from 22 June 1675; the second is the Astronomer Royal for Scotland dating from 1834....

. Halley referred him to George Graham
George Graham (clockmaker)
George Graham was an English clockmaker, inventor, and geophysicist, and a Fellow of the Royal Society.He was born to George Graham in Kirklinton, Cumberland. A Friend like his mentor Thomas Tompion, Graham left Cumberland in 1688 for London to work with Tompion...

, the country's foremost clockmaker
Horology
Horology is the art or science of measuring time. Clocks, watches, clockwork, sundials, clepsydras, timers, time recorders and marine chronometers are all examples of instruments used to measure time.People interested in horology are called horologists...

. He must have been impressed by Harrison, for Graham personally loaned Harrison money to build a model of his marine clock.

It took Harrison five years to build Harrison Number One or H1. He demonstrated it to members of the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

 who spoke on his behalf to 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...

. The clock was the first proposal that the Board considered to be worthy of a sea trial. In 1736, Harrison sailed to Lisbon
Lisbon
Lisbon is the capital city and largest city of Portugal with a population of 545,245 within its administrative limits on a land area of . The urban area of Lisbon extends beyond the administrative city limits with a population of 3 million on an area of , making it the 9th most populous urban...

 on HMS Centurion
HMS Centurion (1732)
HMS Centurion was a 60-gun fourth rate ship of the line of the Royal Navy, built at Portsmouth Dockyard and launched on 6 January 1732. At the time of Centurion's construction, the 1719 Establishment dictated the dimensions of almost every ship being built...

 and returned on HMS Orford
HMS Orford (1698)
HMS Orford was a 70-gun third rate ship of the line of the Royal Navy, launched at Deptford in 1698.. She carried twenty-two 24-pounder guns and four culverins on the lower deck; twenty-six 12-pounder guns on the upper deck; fourteen sakers on the quarter-deck and forecastle; and four 3-pounder...

. On their return, both the captain and the sailing master of the Orford praised the design. The master noted that his own calculations had placed the ship sixty miles east of its true landfall which had been correctly predicted by Harrison using H1.

This was not the transatlantic voyage demanded by the Board of Longitude, but the Board was impressed enough to grant Harrison £500 for further development. Harrison moved on to develop H2, a more compact and rugged version. In 1741, after three years of building and two of on-land testing, H2 was ready, but by then Britain
Kingdom of Great Britain
The former Kingdom of Great Britain, sometimes described as the 'United Kingdom of Great Britain', That the Two Kingdoms of Scotland and England, shall upon the 1st May next ensuing the date hereof, and forever after, be United into One Kingdom by the Name of GREAT BRITAIN. was a sovereign...

 was at war with Spain in the War of Austrian Succession and the mechanism was deemed too important to risk falling into Spanish hands. In any event, Harrison suddenly abandoned all work on this second machine when he discovered a serious design flaw in the concept of the bar balances.
He was granted another £500 by the Board while waiting for the war to end, which he used to work on H3. Harrison spent seventeen years working on this third 'sea clock' but despite every effort it seems not to have performed exactly as he would have wished. Despite this, it had proved a very valuable experiment. Certainly in this machine Harrison left the world two enduring legacies – the bimetallic strip and the caged roller bearing.

The longitude watches



After steadfastly pursuing various methods during thirty years of experimentation, Harrison moved to London in late 1758 where to his surprise he found that some of the watches made by Graham's successor Thomas Mudge
Thomas Mudge (horologist)
Thomas Mudge was an English horologist who invented the lever escapement, the greatest single improvement ever applied to pocket watches.-Early life:...

 kept time just as accurately as his huge sea clocks. It is possible that Mudge was able to do this after the early 1740s thanks to the availability of the new "Huntsman" or "Crucible" steel produced by Benjamin Huntsman sometime in the early 1740s which enabled harder pinions but more importantly, a tougher and more highly polished cylinder escapement to be produced. Harrison then realized that a mere watch after all could be made accurate enough for the task and was a far more practical proposition for use as a marine timekeeper. He proceeded to redesign the concept of the watch as a timekeeping device, basing his design on sound scientific principles.

He had already in the early 1750s designed a precision watch for his own personal use, which was made for him by the watchmaker John Jefferys
John Jefferys (clockmaker)
John Jefferys was an English clockmaker and watchmaker.His parents, John and Jane Jefferys lived in a house called Darbies in the village of Midgham in the parish of Thatcham in Berkshire. His father was a wool merchant. His maternal grandparents were William and Bridgett Yeats. He had at least...

 C. 1752 – 53.
This watch incorporated a novel frictional rest escapement and was also probably the first to have both temperature compensation and Maintaining Power, enabling the watch to continue running while being wound. These features led to the very successful performance of this "Jefferys" watch and therefore Harrison incorporated them into the design of two new timekeepers which he proposed to build. These were in the form of a large watch and another of a smaller size but of similar pattern. However only the larger No. 1 (or "H4" as it sometimes called) watch appears ever to have been finished. (See the reference to "H6" below) Aided by some of London's finest workmen, he proceeded to design and make the world's first successful marine timekeeper that for the first time, allowed a navigator to accurately assess his ship's position in longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

. Importantly, Harrison showed everyone that it could be done. This was to be Harrison's masterpiece – an instrument of beauty, resembling an oversized pocket watch
Pocket watch
A pocket watch is a watch that is made to be carried in a pocket, as opposed to a wristwatch, which is strapped to the wrist. They were the most common type of watch from their development in the 16th century until wristwatches became popular after World War I during which a transitional design,...

 from the period. It is engraved with Harrison's signature, marked Number 1 and dated 1759.

This first marine watch (or "Sea watch" as Harrison called it) is a 5.2" diameter watch in silver pair cases. The movement
Movement (clockwork)
In horology, a movement is the internal mechanism of a clock or watch, as opposed to the case, which encloses and protects the movement, and the face which displays the time. The term originated with mechanical timepieces, whose movements are made of many moving parts...

 has a novel type of escapement which can be classed as a frictional rest type, and superficially resembles the verge escapement with which it is often incorrectly associated. The pallets of this escapement are both made of diamond, a considerable feat of manufacture at the time. The balance spring is a flat spiral but for technical reasons the balance itself was made much larger than in a conventional watch of the period. The movement also has centre seconds motion with a sweep seconds hand. The Third Wheel is equipped with internal teeth and has an elaborate bridge similar to the pierced and engraved bridge for the period. It runs at 5 beats (ticks) per second, and is equipped with a tiny remontoire
Remontoire
In mechanical horology, a remontoire, is a small secondary source of power, a weight or spring, which runs the timekeeping mechanism and is itself periodically rewound by the timepiece's main power source, such as a mainspring...

. A balance-brake stops the watch half an hour before it is completely run down, in order that the remontoire does not run down also.
Temperature compensation is in the form of a 'compensation curb' (or 'Thermometer Kirb' as Harrison put it). This takes the form of a bimetallic strip mounted on the regulating slide, and carrying the curb pins at the free end. During development of No.4, Harrison dispensed with this regulation using the slide, but left its indicating dial or figure piece in place.

H4 took six years to construct and Harrison, by then 68 years old, sent it on its transatlantic trial in the care of his son, William, in 1761. When HMS Deptford
HMS Deptford (1732)
HMS Deptford was a 60-gun fourth rate ship of the line of the Royal Navy, built to the dimensions of the 1719 Establishment at Deptford Dockyard, and launched on 22 August 1732....

 reached Jamaica
Jamaica
Jamaica is an island nation of the Greater Antilles, in length, up to in width and 10,990 square kilometres in area. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harbouring the nation-states Haiti and the Dominican Republic...

, the watch was 5 seconds slow, corresponding to an error in longitude of 1.25 minutes, or approximately one nautical mile. When the ship returned, Harrison waited for the £20,000 prize but the Board believed the accuracy was just luck and demanded another trial. The Harrisons were outraged and demanded their prize, a matter that eventually worked its way to Parliament
Parliament of the United Kingdom
The Parliament of the United Kingdom of Great Britain and Northern Ireland is the supreme legislative body in the United Kingdom, British Crown dependencies and British overseas territories, located in London...

, which offered £5,000 for the design. The Harrisons refused but were eventually obliged to make another trip to the Caribbean city of Bridgetown
Bridgetown
The city of Bridgetown , metropolitan pop 96,578 , is the capital and largest city of the nation of Barbados. Formerly, the Town of Saint Michael, the Greater Bridgetown area is located within the parish of Saint Michael...

 on the island of Barbados
Barbados
Barbados is an island country in the Lesser Antilles. It is in length and as much as in width, amounting to . It is situated in the western area of the North Atlantic and 100 kilometres east of the Windward Islands and the Caribbean Sea; therein, it is about east of the islands of Saint...

 to settle the matter.

At the time of the trial, another method for measuring longitude was ready for testing: the Method of Lunar Distances. The moon moves fast enough, some twelve degrees a day, to easily measure the movement from day to day. By comparing the angle between the moon and the sun for the day one left for Britain, the "proper position" (how it would appear in Greenwich
Greenwich
Greenwich is a district of south London, England, located in the London Borough of Greenwich.Greenwich is best known for its maritime history and for giving its name to the Greenwich Meridian and Greenwich Mean Time...

, England at that specific time) of the moon could be calculated. By comparing this with the angle of the moon over the horizon, the longitude could be calculated.

During Harrison's second trial of "H4" the Reverend 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:...

 was asked to accompany HMS Tartar
HMS Tartar (1756)
HMS Tartar was a 28-gun sixth-rate frigate of the Royal Navy. The ship was designed by Sir Thomas Slade and based on the Lyme of 1748, "with such alterations as may tend to the better stowing of men and carrying for guns."...

 and test the Lunar Distances system. Once again "H4" proved extremely accurate, keeping time to within 39 seconds, corresponding to an error in the longitude of Bridgetown of less than 10 miles (16.1 km). Maskelyne's measures were also fairly good, at 30 miles (48.3 km), but required considerable work and calculation in order to use. At a meeting of the Board in 1765 the results were presented, but they again attributed the accuracy of the measurements to luck. Once again the matter reached Parliament, which offered £10,000 in advance and the other half once he turned over the design to other watchmakers to duplicate. In the meantime H4 would have to be turned over to the Astronomer Royal for long-term on-land testing.

Unfortunately, Nevil Maskelyne had been appointed Astronomer Royal on his return from Barbados, and was therefore also placed on the Board of Longitude. He returned a report of the H4 that was negative, claiming that the "going rate" of the clock, the amount of time it gained or lost per day, was actually an inaccuracy, and refused to allow it to be factored out when measuring longitude. Consequently, the H4 failed the needs of the Board despite the fact that it actually succeeded in two previous trials.

Harrison began working on his H5 while the H4 testing was conducted, with H4 being effectively held hostage by the Board. After three years he had had enough; Harrison felt "extremely ill used by the gentlemen who I might have expected better treatment from" and decided to enlist the aid of King George III. He obtained an audience by the King, who was extremely annoyed with the Board. King George tested H5 himself at the palace and after ten weeks of daily observations between May and July in 1772, found it to be accurate to within one third of one second per day. King George then advised Harrison to petition Parliament for the full prize after threatening to appear in person to dress them down. In 1773, when he was 80 years old, Harrison received a monetary award in the amount of £8,750 from Parliament for his achievements, but he never received the official award (which was never awarded to anyone). He was to survive for just three more years.

In total, Harrison received £23,065 for his work on chronometers. He received £4,315 in increments from the Board of Longitude for his work, £10,000 as an interim payment for H4 in 1765 and £8,750 from Parliament in 1773. This gave him a reasonable income for most of his life (equivalent to roughly £45,000 per year in 2007, though all his costs, such as materials and subcontracting work to other horologists, had to come out of this). He became the equivalent of a multi-millionaire (in today's terms) in the final decade of his life.


Captain James Cook
James Cook
Captain James Cook, FRS, RN was a British explorer, navigator and cartographer who ultimately rose to the rank of captain in the Royal Navy...

 used K1, a copy of H4, on his second and third voyages, having used the lunar distance method on his first voyage. K1 was made by Larcum Kendall
Larcum Kendall
Larcum Kendall was a British watchmaker.-Commission:The Board of Longitude asked Kendall to copy and develop John Harrison's ingenious fourth model of a clock useful for navigation at sea...

, who had been apprenticed to John Jefferys
John Jefferys (clockmaker)
John Jefferys was an English clockmaker and watchmaker.His parents, John and Jane Jefferys lived in a house called Darbies in the village of Midgham in the parish of Thatcham in Berkshire. His father was a wool merchant. His maternal grandparents were William and Bridgett Yeats. He had at least...

. Cook's log is full of praise for the watch and the charts of the southern Pacific Ocean he made with its use were remarkably accurate. K2 was on 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...

, was recovered from Pitcairn Island, and then passed through several hands before reaching the National Maritime Museum
National Maritime Museum
The National Maritime Museum in Greenwich, England is the leading maritime museum of the United Kingdom and may be the largest museum of its kind in the world. The historic buildings forming part of the Maritime Greenwich World Heritage Site, it also incorporates the Royal Observatory, Greenwich,...

 in London.

Initially, the cost of these chronometers was quite high (roughly 30% of a ship's cost). However, over time, the costs dropped to between £25 and £100 (half a year's to two years' salary for a skilled worker) in the early 19th century. Many historians point to relatively low production volumes over time as evidence that the chronometers were not widely used. However, Landes points out that the chronometers lasted for decades and did not need to be replaced frequently – indeed the number of makers of marine chronometers reduced over time due to the ease in supplying the demand even as the merchant marine expanded. Also, many merchant mariners would make do with a deck chronometer at half the price. These were not as accurate as the boxed marine chronometer but were adequate for many. While the Lunar Distances method would complement and rival the marine chronometer initially, the chronometer would overtake it in the 19th century.

Memorials


Harrison died on his eighty-third birthday and is buried in the graveyard of St John's Church, Hampstead along with his second wife Elizabeth and their son William. His tomb was restored in 1879 by the Worshipful Company of Clockmakers
Worshipful Company of Clockmakers
The Worshipful Company of Clockmakers is one of the Livery Companies of the City of London. The Clockmakers were formed by a Royal Charter in 1631. Originally, no person was allowed to sell clocks unless they were a member of the Company. However, such requirements have since been relaxed and later...

 even though Harrison had never been a member of the Company.


Harrison's last home was in Red Lion Square
Red Lion Square
Red Lion Square is a small square on the boundary of Bloomsbury and Holborn in London. The square was laid out in 1698 by Nicholas Barbon, taking its name from the Red Lion Inn. According to some sources the bodies of three regicides - Oliver Cromwell, John Bradshaw and Henry Ireton - were placed...

 in London, now a short walk from the Holborn Underground station
Holborn tube station
Holborn is a station of the London Underground in Holborn in London, located at the junction of High Holborn and Kingsway. Situated on the Piccadilly Line and on the Central Line , it is the only station common to the two lines, although the two lines cross each other three times elsewhere...

. There is a plaque dedicated to Harrison on the wall of Summit House in the south side of the square. A memorial tablet to Harrison was unveiled in Westminster Abbey
Westminster Abbey
The Collegiate Church of St Peter at Westminster, popularly known as Westminster Abbey, is a large, mainly Gothic church, in the City of Westminster, London, United Kingdom, located just to the west of the Palace of Westminster. It is the traditional place of coronation and burial site for English,...

 on 24 March 2006 finally recognising him as a worthy companion to his friend George Graham
George Graham (clockmaker)
George Graham was an English clockmaker, inventor, and geophysicist, and a Fellow of the Royal Society.He was born to George Graham in Kirklinton, Cumberland. A Friend like his mentor Thomas Tompion, Graham left Cumberland in 1688 for London to work with Tompion...

 and Thomas Tompion
Thomas Tompion
Thomas Tompion was an English clock maker, watchmaker and mechanician who is still regarded to this day as the Father of English Clockmaking. Tompion's work includes some of the most historic and important clocks and watches in the world and can command very high prices whenever outstanding...

, "The Father of English Watchmaking", who are both buried in the Abbey. The memorial shows a meridian
Meridian (geography)
A meridian is an imaginary line on the Earth's surface from the North Pole to the South Pole that connects all locations along it with a given longitude. The position of a point along the meridian is given by its latitude. Each meridian is perpendicular to all circles of latitude...

 line (line of constant longitude) in two metals to highlight Harrison's most widespread invention, the bimetallic strip thermometer. The strip is engraved with its own longitude of 0 degrees, 7 minutes and 35 seconds West.

The Corpus Clock
Corpus Clock
The Corpus Clock is a large sculptural clock at street level on the outside of the Taylor Library at Corpus Christi College, Cambridge University, at the junction of Bene't Street and Trumpington Street, looking out over King's Parade. It was conceived and funded by John C...

 in Cambridge, unveiled in 2008, is an homage to Harrison's work. Harrison's grasshopper escapement
Grasshopper escapement
The grasshopper escapement is an unusual, low-friction escapement for pendulum clocks invented by British clockmaker John Harrison around 1722. An escapement, part of every mechanical clock, is the mechanism that causes the clock's gears to move forward by a fixed distance at regular intervals and...

 – sculpted to resemble an actual grasshopper – is the clock's defining feature, even though the appellation 'grasshopper' is a romantic 19th century conceit. Harrison himself probably would have accurately defined it as an "isochronal anchor escapement with pivoted pallets".

Subsequent history


After World War I, Harrison's timepieces were rediscovered at the Royal Greenwich Observatory by retired naval officer Lieutenant Commander Rupert T. Gould.
They were in a highly decrepit state, and Gould then spent many years documenting, repairing and restoring them without being compensated for his efforts. It was Gould, not Harrison, who gave them the designations H1 to H5, although initially he called them simply No.1 to No.5. Unfortunately Gould made some of his own modifications and repairs to these machines that would not pass today's standards of good museum conservation practice, although most Harrison scholars give Gould some credit for having ensured the survival of the historical artifacts as working mechanisms to the present time. Gould is the author of the book The Marine Chronometer, covering the history of chronometers from the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 through to the 1920s. It includes detailed descriptions of Harrison's work and the subsequent evolution of the chronometer. It remains the authoritative work on the marine chronometer.

Today the restored H1, H2, H3 and H4 can be seen on display in the National Maritime Museum
National Maritime Museum
The National Maritime Museum in Greenwich, England is the leading maritime museum of the United Kingdom and may be the largest museum of its kind in the world. The historic buildings forming part of the Maritime Greenwich World Heritage Site, it also incorporates the Royal Observatory, Greenwich,...

 at the Royal Observatory, Greenwich. H1, 2 and 3 are still running; H4 is kept in a stopped state because, unlike the first three, it requires oil for lubrication and will degrade as it runs. H5 is owned by the Worshipful Company of Clockmakers
Worshipful Company of Clockmakers
The Worshipful Company of Clockmakers is one of the Livery Companies of the City of London. The Clockmakers were formed by a Royal Charter in 1631. Originally, no person was allowed to sell clocks unless they were a member of the Company. However, such requirements have since been relaxed and later...

 of London and is on display at the Clockmakers' Museum
Clockmakers' Museum
The Clockmakers' Museum in London, England is a collection of clocks, watches and other horological items which belongs to the Worshipful Company of Clockmakers, which is one of the City of London Livery Companies. It is housed in a gallery at the Guildhall. Admission is free.The Clockmakers'...

 in the Guildhall, London
Guildhall, London
The Guildhall is a building in the City of London, off Gresham and Basinghall streets, in the wards of Bassishaw and Cheap. It has been used as a town hall for several hundred years, and is still the ceremonial and administrative centre of the City of London and its Corporation...

, as part of the Company's collection.

In the final years of his life, John Harrison wrote about his research into musical tuning
Musical tuning
In music, there are two common meanings for tuning:* Tuning practice, the act of tuning an instrument or voice.* Tuning systems, the various systems of pitches used to tune an instrument, and their theoretical bases.-Tuning practice:...

 and manufacturing methods for bell
Bell (instrument)
A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually a hollow, cup-shaped object, which resonates upon being struck...

s. His tuning system, (a meantone
Meantone temperament
Meantone temperament is a musical temperament, which is a system of musical tuning. In general, a meantone is constructed the same way as Pythagorean tuning, as a stack of perfect fifths, but in meantone, each fifth is narrow compared to the ratio 27/12:1 in 12 equal temperament, the opposite of...

 system derived from pi
Pi
' is a mathematical constant that is the ratio of any circle's circumference to its diameter. is approximately equal to 3.14. Many formulae in mathematics, science, and engineering involve , which makes it one of the most important mathematical constants...

), is described in his book Concerning Such Mechanism ........ (CSM). This system challenges the traditional view that "harmonics" occur at integer frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

 ratios, and in consequence all music using this tuning produces low frequency beating. In 2002, Harrison's last manuscript, A true and short, but full Account of the Foundation of Musick, or, as principally therein, of the Existence of the Natural Notes of Melody was rediscovered in the US Library of Congress
Library of Congress
The Library of Congress is the research library of the United States Congress, de facto national library of the United States, and the oldest federal cultural institution in the United States. Located in three buildings in Washington, D.C., it is the largest library in the world by shelf space and...

. His theories on the mathematics of bell manufacturing (using "Radical Numbers") are yet to be clearly understood.http://www.lucytune.com/academic/manuscript_search.html

In television & drama


In 1995, following a major Symposium on the Longitude Problem organized by the National Association of Watch and Clock Collectors
National Association of Watch and Clock Collectors
The National Association of Watch and Clock Collectors is an American non-profit organization with about 18,000 members.The NAWCC was founded in 1943 by members of the Horological Society of New York and the Philadelphia Watchmakers' Guild who wished to create a national organization...

 (NAWCC) at Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

, Dava Sobel
Dava Sobel
Dava Sobel is a writer of popular expositions of scientific topics. She graduated from the Bronx High School of Science and Binghamton University...

 wrote a book chronicling the history of John Harrison's invention entitled Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time
Longitude (book)
Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time is a best-selling book by Dava Sobel about John Harrison, an 18th century clockmaker who created the first clock sufficiently accurate to be used to determine longitude at sea—an important development...

. Although horological historians are of the opinion that Sobel over-dramatised events such as the struggle between Harrison and Maskelyne
Nevil Maskelyne
The Reverend Dr Nevil Maskelyne FRS was the fifth English Astronomer Royal. He held the office from 1765 to 1811.-Biography:...

, her book became the first ever popular bestseller with a theme focused on horology
Horology
Horology is the art or science of measuring time. Clocks, watches, clockwork, sundials, clepsydras, timers, time recorders and marine chronometers are all examples of instruments used to measure time.People interested in horology are called horologists...

.

An illustrated volume co-written with William J. H. Andrewes was printed in 1998: The Illustrated Longitude.

Sobel's book was dramatised for UK television by Charles Sturridge in a Granada Productions film
Granada Productions
Granada Productions was a British commercial television production and distribution company. The company took its name from the successful ITV franchise, Granada Television....

 for Channel 4
Channel 4
Channel 4 is a British public-service television broadcaster which began working on 2 November 1982. Although largely commercially self-funded, it is ultimately publicly owned; originally a subsidiary of the Independent Broadcasting Authority , the station is now owned and operated by the Channel...

 in 1999 under the title Longitude
Longitude (TV serial)
Longitude is a 2000 TV drama produced by Granada Productions and the A&E Network for Channel 4, first broadcast in 2000 in the UK on Channel 4 and the US on A&E. It is an adaptation of the 1997 book of the same title by Dava Sobel...

and was broadcast in the US later that same year by co-producer A&E
A&E Television Networks
A&E Television Networks is a U.S. media company that owns a group of television channels available via cable & satellite in the US and abroad...

. The production starred Michael Gambon
Michael Gambon
Sir Michael John Gambon, CBE is an Irish actor who has worked in theatre, television and film. A highly respected theatre actor, Gambon is recognised for his roles as Philip Marlowe in the BBC television serial The Singing Detective, as Jules Maigret in the 1990s ITV serial Maigret, and as...

 as Harrison and Jeremy Irons
Jeremy Irons
Jeremy John Irons is an English actor. After receiving classical training at the Bristol Old Vic Theatre School, Irons began his acting career on stage in 1969, and has since appeared in many London theatre productions including The Winter's Tale, Macbeth, Much Ado About Nothing, The Taming of the...

 as Gould.

Sobel's book was also the basis for a PBS
Public Broadcasting Service
The Public Broadcasting Service is an American non-profit public broadcasting television network with 354 member TV stations in the United States which hold collective ownership. Its headquarters is in Arlington, Virginia....

 NOVA
NOVA (TV series)
Nova is a popular science television series from the U.S. produced by WGBH Boston. It can be seen on the Public Broadcasting Service in the United States, and in more than 100 other countries...

 episode entitled Lost at Sea: The Search for Longitude.

Harrison's marine time-keepers were an essential part of the plot in the 1996 Christmas special of long-running British sitcom Only Fools And Horses
Only Fools and Horses
Only Fools and Horses is a British sitcom, created and written by John Sullivan. Seven series were originally broadcast on BBC One in the United Kingdom between 1981 and 1991, with sporadic Christmas specials until 2003...

entitled "Time On Our Hands
Time On Our Hands
"Time On Our Hands" is an episode of the BBC sitcom, Only Fools and Horses. It was the final episode of the 1996 Christmas trilogy, and was originally billed to be the last ever episode of the show, it was first screened on 29 December 1996...

". Del Boy
Del Boy
Derek Edward Trotter, better known as "Del Boy", is the fictional lead character in the popular BBC sitcom Only Fools and Horses and one of the main characters of its prequel, Rock & Chips...

 happens to be the owner of a certain marine time-keeper that was lost for centuries, which eventually fetches them £6.2 million at auction at Sotheby's
Sotheby's
Sotheby's is the world's fourth oldest auction house in continuous operation.-History:The oldest auction house in operation is the Stockholms Auktionsverk founded in 1674, the second oldest is Göteborgs Auktionsverk founded in 1681 and third oldest being founded in 1731, all Swedish...

. Harrison's notes and drawings suggest that H6 was built but it has never been found. It looked like an overgrown pocket watch and Harrison scholars still dream of finding it in an attic.

See also

  • 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...

  • History of longitude
    History of longitude
    The history of longitude is a record of the effort, by navigators and scientists over several centuries, to discover a means of determining longitude....

  • Longitude prize
    Longitude prize
    The Longitude Prize was a reward offered by the British government for a simple and practical method for the precise determination of a ship's longitude...

  • Lunar distance (navigation)
    Lunar distance (navigation)
    In celestial navigation, lunar distance is the angle between the Moon and another celestial body. A navigator can use a lunar distance and a nautical almanac to calculate Greenwich time...

  • Horology
    Horology
    Horology is the art or science of measuring time. Clocks, watches, clockwork, sundials, clepsydras, timers, time recorders and marine chronometers are all examples of instruments used to measure time.People interested in horology are called horologists...


External links