John Harrison

Early life

John Harrison was born in Foulby in the West Riding of Yorkshire, the first of five children in his family. His stepfather worked as a carpenter at the nearby Nostell Priory estate. A house on the site of what may have been the family home bears a blue plaque. Around 1700, the Harrison family moved to the 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 and he spent hours listening to it and studying its moving parts.

He also had a fascination with music, eventually becoming choirmaster for the Church of Holy Trinity, Barrow upon Humber.

Harrison built his first longcase clock in 1713, at the age of 20. The mechanism was made entirely of wood. Three of Harrison's early wooden clocks have survived:

The first (1713) is in the Worshipful Company of Clockmakers' collection, previously in the Guildhall in London and since 2015 on display in the Science Museum.

The second (1715) is also in the Science Museum in London.

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 the stately home, has a Victorian outer case with small glass windows on each side of the movement so that the wooden workings may be inspected.

On 30 August 1718, John Harrison married Elizabeth Barret at Barrow upon Humber church. After her death in 1726, he married Elizabeth Scott on 23 November 1726, at the same church.

In the early 1720s, Harrison was commissioned to make a new turret clock at Brocklesby Hall, North Lincolnshire. The clock still works, and like his previous clocks has a wooden movement of oak and lignum vitae. Unlike his early clocks, it incorporates some original features to improve timekeeping, for example, the grasshopper escapement. Between 1725 and 1728, John and his brother James, also a skilled joiner, made at least three precision longcase clocks, again with the movements and longcase made of oak and lignum vitae. The grid-iron pendulum was developed during this period. Of these longcase clocks:

Longitude problem

Longitude fixes the location of a place on Earth east or west of a north–south reference line called the prime meridian. It is given as an angular measurement that ranges from 0° at the prime meridian to +180° eastward and −180° westward. Knowledge of a ship's east–west position is essential when approaching land. Over long voyages, cumulative errors in estimates of position by dead reckoning frequently led to shipwrecks and a great loss of life. Avoiding such disasters became vital in Harrison's lifetime, in an era when trade and the need for accurate navigation were increasing dramatically around the world.

Many ideas were proposed for how to determine longitude during a sea voyage. Earlier methods attempted to compare local time with the known time at a reference place, such as Greenwich or Paris, based on a simple theory that had first been proposed by Gemma Frisius. The methods relied on astronomical observations that were themselves reliant on the predictable nature of the motions of different heavenly bodies. Such methods were problematic because of the difficulty in maintaining an accurate record of the time at the reference place.

Harrison set out to solve the problem directly by producing a reliable clock that could keep the time of the reference place accurately over long intervals without having to constantly adjust it. The difficulty was in producing a clock that was not affected by variations in temperature, pressure, or humidity, resisted corrosion in salt air, and was able to function on board a constantly moving ship. Many scientists, including Sir Isaac Newton and Christiaan Huygens, doubted that such a clock could ever be built and favoured other methods for reckoning longitude, 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; both produced inconsistent results. 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 sort of watch can be found out. But when longitude at sea is lost, it cannot be found again by any watch".

First three marine timekeepers

In the 1720s, the English clockmaker Henry Sully invented a marine clock that was designed to determine longitude: this was in the form of a clock with a large balance wheel that was vertically mounted on friction rollers and impulsed by a frictional rest Debaufre-type escapement. Very unconventionally, the balance oscillations were controlled by a weight at the end of a pivoted horizontal lever attached to the balance by a cord. This solution avoided temperature error due to thermal expansion, a problem which affects steel balance springs. Sully's clock kept accurate time only in calm weather, however, because the balance oscillations were affected by the pitching and rolling of the ship. Still, his clocks were among the first serious attempts to find longitude by improving the accuracy of timekeeping at sea. Harrison's machines, though much larger, are of similar layout: H3 has a vertically mounted balance wheel and is linked to another wheel of the same size, an arrangement that eliminates problems arising from the ship's motion.

In 1716 Sully presented his first Montre de la Mer to the French Académie des Sciences and in 1726 he published Une Horloge inventée et executée par M. Sulli. In 1730 Harrison designed a marine clock to compete for the Longitude prize and travelled to London, seeking financial assistance. He presented his ideas to Edmond Halley, the Astronomer Royal, who in turn referred him to George Graham, the country's foremost clockmaker. Graham must have been impressed by Harrison's ideas, for he loaned him money to build a model of his "Sea clock". As the clock was an attempt to make a seagoing version of his wooden pendulum clocks, which performed exceptionally well, he used wooden wheels, roller pinions, and a version of the grasshopper escapement. Instead of a pendulum, he used two dumbbell balances which were linked together.

It took Harrison five years to build his first sea clock (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 under the command of Captain George Proctor and returned on HMS Orford after Proctor died at Lisbon on 4 October 1736. The clock lost time on the outward voyage. However, it performed well on the return trip: 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.

Longitude watches

After steadfastly pursuing various methods during thirty years of experimentation, Harrison found to his surprise that some of the watches made by Graham's successor Thomas Mudge 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 first 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.

"Jefferys" watch

He had already in the early 1750s designed a precision watch for his own use, which was made for him by the watchmaker John Jefferys c. 1752–1753. This watch incorporated a novel frictional rest escapement and was not only the first to have a compensation for temperature variations but also contained the first miniature going train fusee of Harrison's design which enabled the watch to continue running whilst being wound. These features led to the very successful performance of the "Jefferys" watch, which Harrison incorporated 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 similar pattern. However, only the larger No. 1 watch (or "H4" as it is sometimes called) appears to have been finished (see the reference to "H4" below). Aided by some of London's finest workmen, he proceeded to design and make the world's first successful marine timekeeper that allowed a navigator to accurately assess his ship's position in longitude. Importantly, Harrison showed everyone that it could be done by using a watch to calculate longitude. This was to be Harrison's masterpiece – an instrument of beauty, resembling an oversized pocket watch from the period. It is engraved with Harrison's signature, marked Number 1 and dated AD 1759.

H4

Harrison's first "sea watch" (now known as H4) is housed in silver pair cases some 5.2 inches (13 cm) in diameter. The clock's movement is highly complex for the period, resembling a larger version of the then-current conventional movement. A coiled steel spring inside a brass mainspring barrel provides 30 hours of power. That is covered by the fusee barrel which pulls a chain wrapped around the conically shaped pulley known as the fusee. The fusee is topped by the winding square (requiring a separate key). The great wheel attached to the base of this fusee transmits power to the rest of the movement. The fusee contains the maintaining power, a mechanism for keeping the H4 going while being wound. From Gould: The escapement is a modification of the "verge" fitted to... the common watches of Harrison's day. But the modifications are extensive. The pallets are very small, and have their faces set parallel, instead of at the usual angle of 95° or so. Moreover, instead of being steel, they are of diamond, and their backs are shaped to cycloidal curves... The action of this escapement is quite different from that of the verge, which it appears to resemble. In that escapement, the teeth of the crown wheel act only upon the faces of the pallets. But in this, as will be seen from the points of the teeth rest, for a considerable portion of the supplementary arc—from 90° to 145° (limit of banking) past the dead point—upon the backs of the pallets, and tend to assist the balance towards the extreme of its swing and to retard its return. This escapement is obviously a great improvement upon the verge, as the train has far less power over the motions of the balance. The latter is no longer checked in its swing by a force equal to that which originally impelled it, but by the balance spring, assisted only by the friction between the tooth and the back of the pallet.

In comparison, the verge's escapement has a recoil with a limited balance arc and is sensitive to variations in driving torque. According to a review by H. M. Frodsham of the movement in 1878, H4's escapement had "a good deal of 'set' and not so much recoil, and as a result the impulse came very near to a double chronometer action".

The D-shaped pallets of Harrison's escapement are both made of diamond, approximately 2 mm long with the curved side radius of 0.6 mm, a considerable feat of manufacture at the time. For technical reasons the balance was made much larger than in a conventional watch of the period, 2.2 inches (56 mm) in diameter weighing 28+5⁄8 Troy grains (1.85 g) and the vibrations controlled by a flat spiral steel spring of three turns with a long straight tail. The spring is tapered, being thicker at the stud end and tapering toward the collet at the centre. The movement also has centre seconds motion with a sweep seconds hand.

Death and memorials

Harrison died on 24 March 1776, at the age of eighty-two, just shy of his eighty-third birthday. He was buried in the graveyard of St John's Church, Hampstead, in North London, along with his second wife Elizabeth and later 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 12 Red Lion Square in the Holborn district of London. There is a blue plaque dedicated to Harrison on the wall of Summit House, a 1925 modernist office block, on 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.

The Corpus Clock in Cambridge, unveiled in 2008, is a homage by the designer to Harrison's work but is of an electromechanical design. In appearance it features Harrison's grasshopper escapement, the 'pallet frame' being sculpted to resemble an actual grasshopper. This is the clock's defining feature.

In 2014, Northern Rail named diesel railcar 153316 as the John 'Longitude' Harrison.

On 3 April 2018 Google celebrated his 325th birthday by making a Google Doodle for its homepage.

In February 2020 a bronze statue of Harrison, created by the sculptor Marcus Cornish, was unveiled in Barrow upon Humber.

Later history

After the First World War, Harrison's timepieces were rediscovered at the Royal Greenwich Observatory by the retired naval officer Lieutenant Commander Rupert Gould.

The timepieces were in a highly decrepit state and Gould spent many years documenting, repairing and restoring them, without compensation for his efforts. Gould was the first to designate the timepieces from H1 to H5, initially calling them No.1 to No.5. Unfortunately, Gould made modifications and repairs that would not pass today's standards of good museum conservation practice, although most Harrison scholars give Gould credit for having ensured that the historical artifacts survived as working mechanisms to the present time. Gould wrote The Marine Chronometer, published in 1923, which covered the history of chronometers from the Middle Ages to the 1920s, and which included detailed descriptions of Harrison's work and the subsequent evolution of the chronometer. The book remains the authoritative work on the marine chronometer. Today the restored H1, H2, H3, and H4 timepieces can be seen on display in the Royal Observatory at Greenwich. H1, H2, and H3 still work: H4 is kept in a stopped state because, unlike the first three, it requires oil for lubrication and so will degrade as it runs. H5 is owned by the Worshipful Company of Clockmakers of London, and was previously on display at the Clockmakers' Museum in the Guildhall, London, as part of the Company's collection; since 2015 the collection has been displayed in the Science Museum, London.

In the final years of his life, 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 pamphlet A Description Concerning Such Mechanism ... (CSM). The system challenged 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 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 yet to be clearly understood.

One of the controversial claims of his last years was that of being able to build a land clock more accurate than any competing design. Specifically, he claimed to have designed a clock capable of keeping accurate time to within one second over a span of 100 days. At the time, such publications as The London Review of English and Foreign Literature ridiculed Harrison for what was considered an outlandish claim. Harrison drew a design but never built such a clock himself, but in 1970 Martin Burgess, a Harrison expert and himself a clockmaker, studied the plans and endeavored to build the timepiece as drawn. He built two versions, dubbed Clock A and Clock B. Clock A became the Gurney Clock which was given to the city of Norwich in 1975, while Clock B lay unfinished in his workshop for decades until it was acquired in 2009 by Donald Saff. The completed Clock B was submitted to the National Maritime Museum in Greenwich for further study. It was found that Clock B could potentially meet Harrison's original claim, so the clock's design was carefully checked and adjusted. Finally, over a 100-day period from 6 January to 17 April 2015, Clock B was secured in a transparent case in the Royal Observatory and left to run untouched, apart from regular winding. Upon completion of the run, the clock was measured to have lost only 5/8 of a second, meaning Harrison's design was fundamentally sound. If we ignore the fact that this clock uses materials such as duraluminium and invar unavailable to Harrison, had it been built in 1762, the date of Harrison's testing of his H4, and run continuously since then without correction, it would now (August 2026) be slow by just 10 minutes and 4 seconds. Guinness World Records has declared Martin Burgess' Clock B the "most accurate mechanical clock with a pendulum swinging in free air."

In literature, television, drama and music

In 1995 inspired by a Harvard University symposium on the longitude problem organized by the National Association of Watch and Clock Collectors, Dava Sobel wrote a book about Harrison's work. Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time became the first popular bestseller on the subject of horology. The Illustrated Longitude, in which Sobel's text was accompanied by 180 images selected by William J. H. Andrewes, appeared in 1998. The book was dramatised for UK television by Charles Sturridge in a Granada Productions 4 episode series for Channel 4 in 1999, under the title Longitude. It was broadcast in the US later in the same year by the co-producer A&E. The production starred Michael Gambon as Harrison and Jeremy Irons as Gould. Sobel's book was the basis for a PBS NOVA episode entitled Lost at Sea: The Search for Longitude.

In 1998 the British composer Harrison Birtwistle wrote the piano piece "Harrison's clocks" which contains musical depictions of Harrison's various clocks. The composer Peter Graham's piece Harrison's Dream is about Harrison's forty-year quest to produce an accurate clock. Graham worked simultaneously on the brass band and wind band versions of the piece, which received their first performances just four months apart in October 2000 and February 2001 respectively.

"John Harrison's Hands", a song about the man and his work, was written by Brian McNeill and Dick Gaughan, and has been recorded by both artists and by Show of Hands.

Works

Principes de la montre de Mr. Harrison. Avignon: veuve François Girard & François Seguin. 1767.