This Marine Chronometer Was the First Global Positioning System

The precision of this timekeeping breakthrough enabled the age of European exploration.

harrison watch
National Maritime Museum, Greenwich

Welcome to Watches You Should Know, a biweekly column highlighting important or little-known watches with interesting backstories and unexpected influence. This week: the Harrison H4 Marine Chronometer "Sea Watch."

In fourteen hundred and ninety-two, Columbus sailed the ocean blue…but he didn’t have a clue where — or more importantly, how far — he was going. He just aimed ‘er west and told the boys to floor it. He was headed to India, he thought, but he ended up in the West Indies; that’s how the Lesser Antilles got their popular name. Columbus had no idea how far west India lay, or how long it would take to get there. He just trusted they wouldn’t fall off the edge of the world — where there be dragons, you know.

The problem of longitude — where you are on the planet, east-west speaking — was the thorniest puzzle of the day, or really, of the 18th century. The way southwest from Great Britain to where the riches of the New World lay was really to go south to the correct latitude, which one could easily determine by observing the North Star, then head west until the guy in the crow’s nest yelled, “Land Ho!” Not really efficient.

Thus, in 1714, the British government offered the huge prize of £20,000 (roughly £2 million today) to anyone who could solve the longitude problem once and for all. The competition was to be overseen by a newly created Board of Longitude.

harrison watch
Harrison’s incredible clockwork on display at the National Maritime Museum, Greenwich, England.
National Maritime Museum, Greenwich

All manner of candidate solutions appeared: lunar tables, complex equations based on the sightings of the planets, and many more. The real solution, everybody knew, was to know the precise time where you were on the open ocean and also know the precise time at home. Then it was a simple calculation to figure out how far west — or east — you were. You could do this by sighting the sun at high noon where you were, and if you had a good enough clock for the time back home, you could compare the two and, with some simple mathematics, determine your position.

That was a big if. No one thought such a clock could be built. The best clocks could approach the necessary precision in a rock-steady parlor, but nothing of the kind would do while tossing and turning on a heavy sea. Pocket watches were out of the question, as they kept time to plus or minus a minute a day at best. To win the prize with a timekeeping solution, the watch would need to be good to at least plus or minus 2.8 seconds per day.

In 1714 the British government offered the huge prize of £20,000 (roughly £2 million today) to anyone who could solve the longitude problem once and for all.

Enter a self-trained carpenter from Yorkshire, John Harrison. In the 1720s Harrison was making nice, accurate clocks out of wood. He believed in his clocks strongly enough to toss his hat in the longitude prize ring. These days, we know Harrison’s five marine timekeepers (a uniquely significant term in Harrison’s day) as simply H1, H2, H3, H4, and H5 (note: these names did not come into common usage until 60 years ago, when Harrison biographer and clock restorer Rupert Gould coined them).

john harrison
A print made by Philippe Joseph Tassaert after Thomas King’s portrait of John Harrison.
Philippe-Joseph Tassaert

H1, H2, and H3 were fairly large clocks, ranging in height from 59 centimeters to 66 centimeters (roughly 23-¼-inches to 26-inches) high. Importantly, Harrison’s clocks needed no oil for lubrication. Instead, he designed roller bearings for contact surfaces.

Harrison built H1 between 1730 and 1735. It was essentially a portable version of his wooden clocks, though it was bigger and with several revolutionary improvements to increase precision. H1 proved promising on its trial run to Lisbon, Portugal in 1736; it wasn’t good enough to win the prize, but was encouraging to both Harrison and the Board of Longitude.

Harrison built H2 between 1737 and 1739. H2’s contribution to horology was the remontoir, a device designed to take the variability of the parts manufacturing process out of the timekeeping equation. However, H2 had other problems, and rather than chase his tail trying to fix them, Harrison abandoned H2 and set about building a third timekeeper.

H3 was to prove a major trial for Harrison. At over 700 parts, and subsystems for temperature compensation, a remontoir, and an isochroniser (a device to ensure the clock’s balance wheel swings each way in the same amount of time), the clock was too complex and idiosyncratic to ever work properly. Harrison labored for 19 years before abandoning H3 as the solution to longitude.

Here’s where the story gets interesting. In 1753, Harrison ordered a pocket watch from a London watchmaker. The watch was to be based on Harrison’s own design ideas. When he received the watch, he realized that with certain improvements, it could become the timekeeping answer to the longitude problem. His simple breakthrough discovery was that small, high-frequency oscillators (balance wheels) were much more stable during movement than were larger clocks.

harrisons drawing of watch
Harrison’s designs for his marine chronometers.
Ferdinand Berthoud

H4, just 13 centimeters in diameter, was the result of this realization. The improvements Harrison made included a balance wheel that was much larger than a typical pocket watch. It oscillated at a higher frequency, five times a second — or 18,000 beats per hour. The watch contained a refined version of the temperature compensation Harrison had included in H3, and it contained a miniaturized remontoir.

The one problem, if it could be called that, was that H4 needed oiling. However, Harrison followed a relatively new practice in friction reduction and installed jeweled bearings in several places to minimize friction.

Harrison’s breakthrough discovery was that small, high-frequency oscillators (balance wheels) were much more stable during movement than were larger clocks.

H4 was completed in 1759. The Board of Longitude sent it on two official trials to the West Indies. The timekeeper performed flawlessly on both voyages, but the Board of Longitude was not satisfied. It took until 1765 for the Board to award Harrison half of the prize, and that was conditional upon Harrison’s full disclosure of construction details.

Following Harrison’s disclosures, the Board commissioned a copy of the watch to be made by Larcum Kendall. This watch, known today as K1, was tested on multiple voyages to the South Pacific by none other than Captain James Cook. It too performed flawlessly, and two more were commissioned. One sailed on the Bounty with Captain William Bligh and ended up on Pitcairn Island, where it stayed until returned to the British government in 1840. The other also sailed with Captain Cook on his third voyage to the South Pacific.

Meanwhile, Harrison was getting desperate to “earn” the balance of the Longitude prize. He embarked on H5, a refinement and simplification of H4’s design. With this timekeeper, he sought the support of King George III. The King, a natural philosopher in his own right, tested H5 himself and promised Harrison his support. Ultimately, the King swayed Parliament, and the Board of Longitude capitulated and awarded Harrison the balance of the Longitude prize, plus expenses. The total came to £23,065, very roughly $4 million in today’s dollars. Not bad for a life’s work.

There is more to the story of marine chronometers, of course. They were precise instruments critical to shipping well into the 20th century. But a self-taught Yorkshire carpenter was there first. There is no denying that Harrison’s designs — most especially the large watch known as H4 — are the true forefathers of all modern precision watches.

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