Time in Motion: The Story of the Sea-Clock, or Harrison’s Chronometers.

25 Mar

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.

A marine chronometer clock, of the kind that was common from the late 19th to the late 20th centuries. The clock is housed in a special wooden case and is mounted on a gimbal so that it swivels and pivots. This way, the clock always lies flat, even if the ship is rolling and heaving at sea

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.

H5 (currently unrestored); the last marine chronometer that Harrison made, and the very one which was tested by King George III himself


Posted by on March 25, 2010 in 18th Century


25 responses to “Time in Motion: The Story of the Sea-Clock, or Harrison’s Chronometers.

  1. Jason S. Ganz

    March 31, 2010 at 11:06 AM

    This is clearly the work of a well-researched and spoken gentleman with an interest in the history of time-keeping. While reading this post, I was floored not only by the research done and the chronology of the chronometer as a ship-employed instrument, but the pictures that showed not only the clocks as they evolved, but also the internals. The technology that we as contemporaries take for granted such as GPS, Casio G-shocks, etc., has really only come to being because of research done by previous persons such as Mr. Harrison and Son… We would not know where we are unless we had a rudimentary, time based, mechanism that could compensate for the undulations at sea, that could keep time relative to these two points (start and destination).

    One other thing that amazes me is just how corrupt people were, something most take as a new concept, but is paraphrased in Hobbes’ “The Leviathan”. Maskelyne is exactly the personification of Hobbes’ stereotype… self-interested, and willing to screw others over for self-advancement… and while Harrison and son received 8,350 pound sterling, I’m sure that it was merely a pittance compared to the financial and emotional hardships provided both Maskelyne and the Board of Longitude. The loss of faith in humanity isn’t a new thing sadly, but it makes me happy to see people continue to improve on the available and overcome adversity to see their dreams come true.

    Well-written Shahan… Well-done 🙂

    Jason S. Ganz

  2. Mike Nielsen

    July 22, 2010 at 12:45 AM

    yes, very interesting. I hold Mr. Harrison in the highest regard. A most inspiring story of determination and patience. A great story of how one’s education and class status does not dictate your ability to contribute and make a difference in the world. I wish more people were as industrious and inventive as he. May I suggest the history book, a very quick and engaging read, called “Longitude” by Dava Sobel

  3. Oleg Pestryakov

    November 16, 2010 at 10:14 AM

    Certainly such result impresses. To create a pocket mechanical clock with such accuracy of a course in a XVIII-th century. Even now to receive such accuracy it is necessary to use some quartz resonators and to summarize their signal by means of the processor.

  4. Mark Wilkerson

    January 22, 2011 at 3:33 PM

    A facinating read. PBS broadcast a documentary on this very father son team and their challenges, a few years back. My question I ask my class sometimes is “who in the village had the second clock”? Mostly the clergy and/or the King/Queen “owned” the first clock. When did the “trades and Masons” gain power to determine when the day begins and ends?

  5. waverly

    February 2, 2011 at 7:25 AM

    thanks so much for this website, I’m doing a research report on the very thing and it helped a lot!!! very interesting!!

  6. Colin Willett

    January 8, 2012 at 1:44 AM

    I’ve just learned that King George III was not the ‘idiot’ he is made out to be. Apparently ‘idiot’ George III was the one who proved that Harrison’s watch had the accuracy that was required, took on himself the longitude Board and his Astronomer Royal and Parliament to support Harrison’s claim for the prize money. And apparently, it was through the development of Harrison’s watches and George III efforts that led to the Britain’s colonial expansion and extreme wealth.

  7. Mampei

    February 6, 2012 at 4:47 PM

    Thank you for bloggin about this. I needed this information for my project I am doing. Again, thanks a lot.

  8. longitude fan

    September 27, 2012 at 6:58 AM

    Harrison is a personal hero of mine. You have done him proud. Thank you.

    • scheong

      September 27, 2012 at 8:56 AM

      Thank you! I’m glad you liked it.

  9. Moying

    October 28, 2012 at 1:37 PM

    Reblogged this on Moying's WordPress.

  10. macswriter

    November 27, 2012 at 4:18 PM

    Thanks for this blogpost. It was just what I was looking for as I’m researching a book that involves various member of the Royal Society, including Maskelyne. He sure was a ba***rd, eh? Thankfully King Geo got Harrison part of his cash. I wonder what happened to Joseph in the end?

    • scheong

      November 27, 2012 at 5:42 PM

      You’re welcome. I never figured out what happened to Joseph Harrison. I couldn’t find much information on him.

  11. David Mosely

    December 28, 2012 at 1:44 AM

    Please clarify this Joseph person. All other documentaries refer to harrisons son William who took the watch on its sea testing. I dont think there was a ‘Joseph’.

    • scheong

      December 28, 2012 at 8:36 AM

      Hi David, yeah I made a mistake! You’re the first person to notice it…

      John Harrison is the clockmaker. William is his son.

      JOSEPH HARRISON is John’s BROTHER. I.e. William’s Uncle. That’s what I seem to recall from my research. It was mentioned in a documentary I watched once.

      • Richard Gilbreath

        February 17, 2016 at 2:12 AM

        In the film John’s brother Joseph wasn’t mentioned, but his brother James was.

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  13. Olaf

    May 20, 2014 at 5:08 PM

    Just like to mention that the last 2 images are not visible.
    Maybe removed or misspelled the filename. Note that it may work on tour local PC. Severs are almost always case-sensitive,

  14. Cliff Larsen

    May 31, 2014 at 11:39 AM

    Great read.Many thanks

    • scheong

      May 31, 2014 at 5:41 PM

      Hi Cliff, thanks. Glad that you enjoyed it.

  15. Xinhua Weng

    August 12, 2014 at 1:16 AM

    Minor error in the following statement (1 degree = 4 minutes).

    “a minute lost or gained at sea meant being off your position by as much as four degrees.”

  16. DK

    January 25, 2015 at 10:51 PM

    very good info!

  17. notatsignal

    May 26, 2015 at 2:51 PM

    It came to my attention sort of recently that the reason the Carpathia took so long to find the survivors of the R.M.S Titanic was that the position that the Radio Man relayed to them was incorrect. 2nd. Mate Lightoller had done the sextant readings just before dark and recorded the time by his watch. Normally, those readings would be checked later against the Ship’s Cronometer and corrected. Lightoller was never able to perform that part of the task. His watch was a few seconds off, and the bearings that the radio Man was given hadn’t been corrected. The Carpathian was directed to a place nearly 13 miles from the actual location of the wreck site.


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