The Story of the Sea-Clock, or Harrison’s Chronometers.

Special Note: This article will concentrate on the life work of Mr. John Harrison, an 18th century clockmaker who, through literally decades of work, changed maritime navigation forever. It is not meant to be an in-depth look at the history of finding longitude, which is something that would take up the space of several articles!
A Problem at Sea
These days, navigation at sea is pretty easy. You have GPS, you have radio, you have compasses, clocks, maps and a million other navigational aids to get your ship from A to B nice and safe…dependent, of course, on the weather. But that’s now in the 21st Century. Three hundred years ago, maritime navigation was nowhere near as easy. Mariners were in constant danger of getting lost at sea due to not knowing where they were, how far they had travelled and how far they still had to go. On a ship at sea with limited supplies and limited time to find safe harbour, not knowing your position was a serious safety-hazard.
As everyone who’s passed highschool geography ought to know, the world is divided up in a grid by lines of latitude (horizontal lines that wrap around the earth and which stack up on each other), and lines of longitude, which go around the earth from east to west, meeting at the North and South Poles at the top and bottom of the globe. Back in the early 1700s and even before this, taking one’s ship out to sea was a dangerous endeavour. Once beyond the sight of land, it was very difficult to fix one’s position, and therefore know how far your ship had travelled.
The position of the sun changes at noon, due to the curvature of the earth; this is why at extreme points on the earth, such as near the poles, you might have full sun at midnight and nothing at all at midday. Sailors were able to determine their north-south latitude position by measuring the angle of the sun at noon against the horizon. This measurement obtained, they were able to mark on a chart, how far north or south they were of the midpoint of latitudes, the Equator. However, finding out how far east or west you were of a given position was considered impossible, because this required knowing very accurately, what the time was.
“Okay so you need to know what the time is to find your spot on the earth. Get a clock or a watch, dunk it on the ship and let’s go!” you probably say.
It isn’t that easy.
Clocks in the 17th and 18th centuries were large pendulum clocks (also called ‘grandfather’ clocks). Although a pendulum clock could keep almost perfect time on land, its ability to keep accurate time at sea was greatly diminished due to the fact that sailing ships rock, pitch, roll and sway on the ocean waves. Such aggressive movements threw the pendulum’s swing (and thus, the clock’s timekeeping abilities) off-beat, rendering the clock useless. The only watches available were old-fashioned pocket-watches, which, although they required no stable surface to keep time, unlike the pendulum clock, they were often not manufactured to such a level of quality as to keep time accurately at sea. Pocket-watches often varied several minutes a day. While to us a minute of difference either way doesn’t sound serious, a minute lost or gained at sea meant being off your position by as much as four degrees. If again, this doesn’t sound serious, it actually meant the possibility of being off your course and position by a matter of several miles.
Telling Time at Sea
While there were several proposals put forward on how to accurately determine a ship’s longitude, the one which most people are familiar with today, is the one involving time. The earth revolves at a constant rate. A full 360 degrees in twenty-four hours, or fifteen degrees each hour. By knowing the time at two places at once, a navigator could calculate fairly easily, his ship’s position of longitude.
If a ship left England at noon and sailed for America, it would be able to determine its position by checking the time on its sea-clock or marine chronometer, as is the correct term. When the chronometer showed it was noon in England, the navigator had to wait until it was noon onboard his ship and record the time-difference. A difference of two hours meant the ship had travelled thirty degrees (since the earth turns 15 degrees each hour). In theory, this was simple, but as I mentioned, the clocks available in the 1700s meant that keeping accurate time at sea was all but impossible.
John Harrison
After a series of catastrophic shipwrecks in the early 1700s, it was decided that the British Government had to put some serious thought into the safety of British sailors. In 1714, the year that King George I came to the throne and heralded the start of the Georgian Era, a board was set up, called the Board of Longitude. Its purpose was to judge and examine any and all schemes for successfully determining a ship’s position of longitude at sea. A prize of twenty thousand pounds sterling, was offered to any person or group of persons who successfully produced a device or a method by which longitude could be accurately determined at sea.
Enter John Harrison.
You couldn’t possibly find a more unlikely person to be the man who would change history so momentously, and who tackled the biggest technological problem of his generation. John Harrison was born in 1693. In 1714, he was a mere twenty-one years of age. John was born in the village of Foulby in West Yorkshire, the first of five children. His father made a modest living as a carpenter.
In 1700, the Harrison family moved to the village of Barrow-Upon-Humber in North Lincolnshire, the village where Harrison would spend almost the rest of his life.
In the 18th century it was common for children to follow their parents into their chosen professions. Watchmakers gave birth to watchmakers, lawyers to lawyers and carpenters to carpenters. With his father’s occupation as a carpenter, it was inevitable that John Harrison would follow his father into the woodworking trade. Only, instead of working on furniture, young John concentrated on something else. Clocks. He spent countless hours examining, disassembling and reassembling clocks and watches, until he knew them as well as he knew himself. One legend goes that when he was sick with smallpox in 1699, he was given a pocket watch to play with while in bed. He spent hours winding up the watch, holding it in his hands, looking at it, listening to it and opening it up to look at all the fiddly little moving parts inside it. By his early twenties, Harrison, who had previously been a bellringer at the local church as well as an apprentice carpenter to his father, officially decided that he would become a clockmaker. He completed his first, fully-functional clock in 1713 at the age of twenty.
Harrison was very good at what he did. A perfectionist with perhaps a slight twinge of Obsessive-Compulsive Disorder, Harrison went over his pendulum clocks over and over and over again, checking and re-checking everything to make his machines more accurate. Considering that Harrison never had any formal education, never went to school and never went to university, he was doing very well in understanding such complex machines as mechanical clocks. Harrison had quite a reputation for his clocks. In an era where a good clocks kept time to a few minutes a week, Harrison’s clocks boasted accuracy to a few SECONDS a MONTH.

This clock, manufactured almost entirely of wood, was completed by John Harrison in 1717, at the age of 24!
The Longitude Prize
Sooner or later, Harrison was bound to find out about the longitude prize. With his background in clockmaking, Harrison was quick to grasp the fact that knowing one’s position at sea was best determined by knowing accurately, the time in two places at once: Onboard ship and at a home port. Unfortunately, as he also realised, such clocks as those which existed in the 1700s, were woefully inaccurate for the task which they would have to perform. Harrison, like so many others before him, recognised these problems with a clock keeping time at sea.
1. Temperature. Mechanical timepieces keep different times in different temperatures. Hot temperatures cause them to slow down, cold temperatures cause them to speed up. This is due to the wood or the metal inside the timepiece reacting to the temperature around it.
2. Humidity. Moisture affects how smoothly a clock runs. Condensation brought about by rapid temperature-changes could cause a clock to rust or collect water, which would slow it down.
3. Motion. The rocking, rolling, plunging and heaving of early sailing-ships meant that the clock or watch would be subjected to massive amounts of sudden and violent movement. A significant enough jolt, such as that produced by a ship sliding down the trough between two waves to impact against the next wave coming foward, would be enough to throw a clock off its accuracy, rendering it useless. And even without the storms, a swaying, rocking ship would not allow a clock’s pendulum to swing back and forth reliably enough to keep time.
To solve all these problems, Harrison knew he had to do some very careful thinking. By the 1720s, Harrison’s experience in clockmaking and timekeeping was significant. His fanaticisim with accuracy meant that he tested his clocks to make sure that they kept perfect time under every single variation he could think of. He solved the problem of clocks keeping time through temperature-differences by placing two clocks in two rooms in his house during a frigid day in winter. He built a great fire in the fireplace of one room and kept the other room freezing cold. He synchronised both clocks and then kept a check on how fast or slow each of the clocks were and adjusting their pendulums correctly.
Despite never having gone to school, despite never being taught how to read and write except through his own determination, Harrison wrote reams and reams of paper, covering his research into the affects of temperature, lubrication and the use of various metals had on his clocks. After years of research and experimentation, Harrison was ready to have a shot at the Longitude Prize.
There was just one problem.
Due to the great inaccuracy of clocks at the time, no scientist, naval or government official believed that any clock could be produced that would ever keep time at sea. This prejudice against clocks was widespread and it even included one of the most famous scientists of the day: Sir Isaac Newton. Harrison knew that he would have to be incredibly good with his work if he ever had a chance of claiming his twenty-thousand pound prize.
Time and Patience
Harrison made a total of five marine chronometers in his life, three clocks and two pocket-watches. His first clock, “H1″, was presented for trials in 1736. Harrison was forty-three years old.

A model of H1. The two counterweights at the top of the clock (linked by the metal coil in the middle) were designed to swing back and forth, to act as shock-absorbers against the rock and roll of the ship
H1 was taken for trials and Harrison accompanied his creation on his first and only trip to sea. His ship, the HMS Centurion, travelled from England to Portugal, docking in Lisbon. From there, Harrison caught the HMS Orford back to England. The crew of the Orford were much impressed by Harrison’s newfangled invention and praised him for his efforts. The Board of Longitude was also sufficiently impressed to pay him two hundred pounds sterling towards the development of another clock.
Harrison’s next clock, H2 was completed a few years later. Harrison knew that his clock had to be stronger and tougher. It was a machine, not a showpiece. This clock was more boxy and compact than H1, but it kept time just as well.

An old photograph of H2
The War of Austrian Succession (1740-1748) meant that Harrison wasn’t allowed to take his newest sea-clock on a trial voyage. Military officials were worried that the clock might fall into enemy hands. Instead, the Board of Longitude gave Harrison another five hundred pounds towards further development of his machines. The result was H3.

John Harrison’s marine chronometer officially called “H3″
While Harrison was happy with H3, he soon decided that he’d been wasting his life all these decades. While Harrison’s clocks all kept wonderful time and while they could be used at sea successfully, Harrison just wasn’t convinced that this was the right way to go. Clocks were bulky, expensive, delicate machines that took up space on a ship which had very little space to give. Frustrated, Harrison gave up on trying to make marine clocks and instead did a complete, 180-degree turn and considered manufacturing a marine watch instead.
The watch in the 18th century was the pocket-watch. A large, round, bulky thing, but small for the period. Most watches were expensive, but kept only mediocre time. Harrison was sure that he could improve on then-current designs, and come up with a masterpiece.
To help him in this endeavour, Harrison consulted a man named John Jeffreys, a professional watchmaker. Jeffreys agreed to manufacture a pocket watch for Harrison. But there was one catch. It was to Harrison’s own personal design. Jeffreys accepted the challenge and set to work.
When the watch, now known as “H4″, was completed, it was so incredibly accurate that Harrison was probably slamming his head against the wall at his own stupidity for wasting his life fiddling around with clocks instead of pocket-watches! H4 took six years to complete and was finally ready for testing in 1761, by which stage Harrison was nearly seventy years old!
Far too old to go to sea again, Harrison’s son, Joseph, agreed to test his father’s watch. Joseph boarded a ship, the HMS Deptford and set sail for Jamaica. After weeks at sea, Joseph Harrison determined that his father’s watch was off by a mere…five seconds.

Harrison’s masterpiece: H4
The Board of Longitude were not pleased. And neither would you be, if everything you said was wrong was suddenly proven right, and a watch or a clock could keep accurate time at sea! The father-son team of John and Joseph Harrison awaited their prize-money of twenty thousand pounds.
Which never came.
The Board of Longitude demanded another test. The outraged Harrisons had no choice but to oblige them, if only to prove them wrong, and Joseph Harrison packed his bags for another voyage, this time to Barbados. The watch didn’t fare quite so well this time, with Joseph making the inaccuracy to be thirty-nine seconds out. But things were made even worse by the appearance of a man named Nevil Maskelyne.
Maskelyne was easily Harrison’s arch-rival in the race for the Longitude Prize. Maskelyne was a proponent of the ‘Lunar Distance’ method of determining longitude at sea.
The moon moves at a constant rate around the earth; twelve degrees a day. By measuring the angles between the moon and sun before one left England and measuring these angles later when the moon was over the horizon, one could determine how far one had travelled.
There was one big problem with Maskelyne’s lunar-distance method. It was highly complicated; and most seamen were not mathematics whizzes who specialised in geometry. While Maskelyne’s method did work, Harrison believed it wholly impractical at sea due to how long it would take to calculate distance.
Claiming the Prize
Upon Joseph’s return to England, the Harrisons once again presented their results to the Board of Longitude. This time, the Board could not ignore the papers in front of them. Once is beginner’s luck. But…twice?
The Harrisons demanded their prize and were eventually offered ten thousand pounds sterling, if they agreed to turn over H4 for duplication by other watchmakers. The Harrisons did so, but the money was not forthcoming. In a twist of fate that must’ve made John Harrison rip his hair off his head, his rival, Maskelyne, was made Astronomer Royal, and thus, a member of the Board of Longitude, who could therefore influence the Board’s decisions. Maskelyne managed to find a loophole in the criteria for claiming the prize-money and effectively told the Harrisons to get lost and that they weren’t allowed the twenty thousand pounds.
Infuriated, Joseph Harrison took a pen and a piece of paper and in a very bold move, wrote directly to the one man he was sure could help him and his father claim the money which they knew was theirs.
While Joseph worked on his letters, John went back to watchmaking. In the 1760s and 70s, he created his fifth and final marine chronometer, H5. In 1772, Joseph finally had success.
The two Harrisons had managed to obtain a private audience with the King of England.
King George III listened patiently while the father and son team beat out their case in front of him. His Majesty was moved by their plight and was obviously not pleased at what was happening. He whispered to an aide that the two men had been “cruelly wronged”. After much consideration, George III took Harrison’s latest creation, H5, and performed accuracy tests on it himself, checking its timekeeping day in and day out for ten weeks, from May to July in 1772. George III, though famous for going positively looney, deaf and blind towards the last years of his life, was, amongst other things, an avid lover of science and technology. His observations told him that H5 kept time to 1/3 of a second a day! A phenomenal feat of accuracy in a day and age when a regular pocket-watch kept time to a minute a day! Eventually, the king called the Harrisons before him and advised them on a course of action. He suggested that the two Harrisons petition Parliament into giving them the twenty thousand pounds of prize-money and told them that if Parliament refused, to further add that the king himself would enter the chamber and give the entire house a good talking-to.
Well…no politician wants to be told off in public by his king.
Finally, in 1773, John Harrison got…well…some money. Eight-thousand, seven hundred and fifty pounds sterling, from Parliament, for his efforts.
If we add up all of the money that Harrison recieved for his work, we’ll find that it totals a whopping twenty-three thousand and sixty-five pounds! However, the official Longitude Prize of twenty-thousand pounds was never awarded to anyone, even though it should rightly have gone to John and Joseph Harrison.
Even when Harrison realised how much money he was making, he still wasn’t happy. He’d never recieved the public recognition of his achievements that he’d hoped for. It was as if the people in charge turned red-faced with embarrassment, shoved over a pouch of gold and then slammed the door in his face. By now, Harrison was eighty years old. Harrison had spent almost literally, his whole life trying to solve the biggest technological problem of his age, and he was never even thanked properly.
In the end, Harrison died at the age of eighty-three, barely able to live in retirement for a decent length of time to enjoy his riches. He passed away, aged 83, on the 24th of March, 1776. Ironically…the date of his death, was also the date of his birth, exactly 83 years before in 1693. He was buried in the churchyard of St. John’s Church, in Hampstead, London, alongside his second wife, Elizabeth, and their son William.
Harrison’s Legacy
Some people say that an artist’s work is never truly appreciated until they’re dead. In Harrison’s case, this was almost certainly it. Although he never recieved the fame, fortune and acclaim that he had hoped for in his own lifetime, Harrison’s lifetime of work saw the expansion of the British Empire by making sea-travel much, much safer.
And yet…despite all his efforts, marine chronometers were not widely used, initially. Their high manufacturing cost meant that these amazing machines were out of the reach of all but the wealthiest of seamen; those who had made lots of money as merchant captains or officers in the Navy, who could afford to purchase an expensive and accurate sea-clock for their ships. But as years went by, the use of marine chronometers eventually increased, until they were declared obsolete in the late 20th century, by the coming of GPS.
Harrison’s clocks and watches were rediscovered in the early 20th century by Rupert Thomas Gould, a Royal Navy officer. He is credited with documenting, examining, restoring and preserving Harrison’s clocks and saving them from total destruction. It is thanks to his research and restoration-skills that H1, H2, H3, H4 and H5 are still around today. H1-3 have been reassembled and restored to operational condition. They may be seen at the National Maritime Museum at the Royal Observatory, Greenwich, England. H4 is also restored, but H5 still requires restoration. Only H1, 2 and 3 are in operation, however, since H4 and H5 require significant lubrication to operate successfully, whereas H1, 2 and 3 do not.

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