John Harrison

John Harrison (24 March 1693 – 24 March 1776) was an English clockmaker. He invented the marine chronometer, a long-sought and critically-needed key piece in solving the problem of accurately establishing the East-West position, or longitude, of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age of Sail. The problem was considered so intractable Parliament offered what was at the time a huge fortune for a solution, a prize of £20,000 (roughly £6 million or €7.7 million in 2007 terms).

Early life

John Harrison was born in Foulby, near Wakefield, in West Yorkshire, where his father worked as a carpenter at the nearby Nostell Priory estate. The house where he was born now bears a blue plaque.

Around 1700, the family moved to the North Lincolnshire village of Barrow upon Humber. Following his father's trade as a carpenter, Harrison built and repaired clocks in his spare time. Legend has it that at the age of six while in bed with smallpox, he was given a watch to amuse himself, supposedly spending hours listening to it and studying its moving parts. As clocks and watches of all kinds were rare and expensive at the time, and Harrison came from a family of only modest means, it is likely the legend is false or the timepiece was broken enough to be worth little.


Harrison built his first longcase clock in 1713, at the age of 20. The mechanism was made entirely of wood, which was not a curious 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' Collection in Guildhall;. the second (1715), is in the Science Museum; the third (1717) is at Nostell Priory in Yorkshire, the face bearing the inscription "John Harrison Barrow". The Nostell example, in the billiards room of this fine stately home, has a Victorian outer case, which has been thoughtfully provided with small glass windows to each side of the movement so that the wooden workings may be inspected.

He was a man of many skills and used these to systematically improve the performance of pendulum clocks. He invented the gridiron pendulum, consisting of alternating brass 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 — a control device for the step-by-step release of a clock's driving power. Being almost frictionless, it required no lubrication.


Overview of the problem

A longitude describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. Longitude is given as an angular measurement 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, for instance, one would want to revisit the location or place it on a map). The practical methods relied on a comparison of local time with the time at a given place (such as Greenwich or Paris). Many of these methods relied on astronomical observations relying on the predictable, "clockwork" nature of motions of heavenly bodies.

Harrison instead set out to solve the problem in probably the most direct way: by producing a reliable clock. The theory was simple and had been first proposed by Frisius. 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 and humidity. Frisius had realized that to determine longitude, a clock would have to be “of great exactness”. Many leading scientists including Newton 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 and a spiral balance spring 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 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.

After steadfastly pursuing various methods during thirty years of experimentation, Harrison finally designed and built the world's first successful marine chronometers, the highly accurate maritime time-keeping instruments that, for the first time, allowed a navigator to accurately assess his ship's position in longitude. This is so because the earth is constantly rotating, and therefore knowing the time whilst 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 frequently led to shipwrecks and lost lives. Avoiding maritime tragedies became 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 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 whilst 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 accurately, making the device a fundamental key to the modern age. Nonetheless, for many years even after the American Revolution, chronometers were expensive rarities, as their adoption and use proceeded slowly due to the precision manufacturing necessary and hence high expense, but by the early 19th century, navigation at sea without one was considered unwise to unthinkable. Using a chronometer to aid navigation 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

In 1730 Harrison created a description and drawings for a proposed marine clock to compete for the Longitude Prize and went to London seeking financial assistance. He presented his ideas to Edmond Halley, the Astronomer Royal. Halley referred him to George Graham, the country's foremost clockmaker. 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 who spoke on his behalf to the Board of Longitude. The clock was the first proposal that the Board considered to be worthy of a sea trial. In 1736, Harrison sailed to Lisbon on HMS Centurion and returned on HMS Orford. 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 was at war with Spain in the War of Austrian Succession and the mechanism was deemed too important to risk falling into Spanish hands. He was granted another £500 by the Board while waiting for the war to end, which he used to work on H3. By 1755 he had become convinced that large machines were not suitable for a marine timekeeper. H3 had proved a very valuable experiment, teaching Harrison greatly about the overall design and making of balance springs and it left the world two enduring legacies — the bimetallic strip and the caged roller bearing.

The longitude watches

Based on a watch made to his designs by John Jefferys, he proposed to build two new timekeepers, a larger and a smaller watch. It was the larger H4 that was to be his masterpiece — an instrument of beauty, having the shape of a large pocketwatch but the size of a soup plate.

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 reached Jamaica, 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, which offered £5,000 for the design. The Harrisons refused but were eventually obliged to make another trip to the Caribbean city of Bridgetown on the island of Barbados 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 (or more typically over Greenwich), the "proper position" of the moon could be calculated. By comparing this with the angle of the moon over the horizon, the longitude could be calculated.

On Harrison's second H4 trial, the Reverend Nevil Maskelyne was asked to accompany HMS Tartar and test the Lunar Distances system. Once again H4 proved almost astonishingly accurate, keeping time to within 39 seconds, corresponding to an error in the longitude of Bridgetown of less than . Maskelyne's measures were also fairly good, at , but required considerable work and calculation in order to use. At a meeting of the Board in 1765 the results were presented, and once again they could not believe it was not just 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 "drift 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.

James Cook used K1, a copy of H4, on his voyages. K1 was made by Larcum Kendall, who had been apprenticed to John Jefferys. 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, was recovered from Pitcairn Island, and then passed through several hands before reaching the National Maritime Museum 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. As well, 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.


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

Harrison's last home was in Red Lion Square in London, now a short walk from the Holborn Underground station. 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 on 24 March 2006 finally recognising him as a worthy companion to his friend George Graham and Thomas Tompion, "The Father of English Watchmaking", who are both buried in the Abbey. The memorial shows a meridian 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.

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 through H5. Although Gould made some repairs to these machines that would not pass today's standards of good museum conservation practice, Harrison scholars mostly give Gould 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 through to the 1920s. It includes detailed descriptions of Harrison's work and the subsequent evolution of the chronometer. It still 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 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 degrades when run. H5 is owned by the Worshipful Company of Clockmakers of London and is on display at the Clockmakers' Museum in the Guildhall, London, as part of the Company's collection.

In the final years of his life, John Harrison wrote about his research into musical tuning and manufacturing methods for bells. His tuning system, (a meantone system derived from pi), is described in his book Concerning Such Mechanism ........ (CSM). This system challenges the traditional view that "harmonics" occur at integer 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" - crossed out) 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. His theories on the mathematics of bell manufacturing (using "Radical Numbers") are not clearly understood.

In television & drama

In 1995, following a major Symposium on the Longitude Problem organized by the National Association of Watch and Clock Collectors (NAWCC) at Harvard University, Dava Sobel 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. Although many horological historians feel that Sobel emphasized the struggle between Harrison and Maskelyne into a personalized conflict in order to create more drama and to capture her readers' attention the book became the first ever popular bestseller with a theme focused on horology.

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 for Channel 4 in 1999, and was broadcast in the US later that same year by co-producer A&E. The production starred Michael Gambon as Harrison and Jeremy Irons as Gould.

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 entitled "Time On Our Hands". Del Boy 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. 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 the attic.

See also

External links



  • Sobel, Dava (1995). Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. New York: Penguin. ISBN 0-14-025879-5.
  • Sobel, Dava & Andrewes, Willam J.H. (1998). The Illustrated Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. New York: Walker Publishing Co.. ISBN 0-8027-1344-0.

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