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On a gray and stormy day in October 1707, British Admiral Sir Cloudesley Shovell lead his fleet through the Strait of Gibraltar and back to England after a series of victorious skirmishes with the French Navy in the Mediterranean Sea. Despite the rough Atlantic weather, his navigators were confident the British ships were far enough west to avoid the notoriously treacherous Scilly Isles off the coast of Brittany in northern France. Legend has it a young crew member tried to warn senior officers that the admiral’s navigation was faulty, and for this mutinous presumption he was hanged.
As night fell and dense fog rolled in, four of the six warships crashed onto the island’s reefs and rocks and quickly sank. About 2,000 thousand sailors died, and for several days drowned men and ship wreckage washed ashore.
As one of the worst maritime disasters in British history, this helped focus attention to the age-old challenge of plotting a ship’s longitude at sea. Latitude was rather easy to discern. A navigator could figure out his ship’s position north or south of the equator by observing the sun’s position. An east-to-west longitude bearing, however, was problematic.
To calculate longitude at sea, a navigator needed to reliably compare the time on the ship to the time at a port where longitude was known. It was almost impossible to keep accurate time at sea, because motion and temperature tended to negatively affect clocks and time pieces of the day. Travel at sea was very dangerous when you didn’t know exactly where you were going.
To solve this navigational dilemma, the British Parliament passed the Longitude Act of 1714 under advisement of the esteemed scientist Sir Isaac Newton. Queen Anne appointed a blue-ribbon panel of astronomers, mathematicians and navigators to oversee prize rewards (totaling several million pounds by today’s value) for solving the age-old problem of finding longitude at sea.
News of the prize spread quickly in the seafaring nation. As you might expect, the prize money attracted all sorts of solutions from both learned men and quacks. Most of the early proposals were inadequate or so off the mark that the Prize Panel didn’t bother to meet to consider a proposal until 1736.
Most scientists looking to solve the longitude problem focused on charting location at sea via the movement of the moon among the stars. Given their expertise, most of the blue-ribbon panel believed the “clock of the heavens” held the eventual answer. Some had pondered a celestial remedy for decades.
John Harrison, in contrast, was a carpenter of humble means who began designing clocks in 1713 when he was just shy of his 20th birthday. Harrison’s clocks were mostly made of wood, which leads historians to believe he was self-taught. Harrison designed his clock gears from oak, a tough hardwood that didn’t wear down. He carved other clock parts that were traditionally made of metals and needed oil lubrication from lignum vitae, a dense tropical hardwood that exudes its own oil.
His wooden clock designs seem to indicate he was thinking about the unique technological problems of keeping accurate time at sea without metal that rusted in damp conditions and oil that got thicker or thinner depending on the temperature.
Harrison took his first trip to London in 1730 to meet with Dr. Edmond Halley, England’s royal astronomer. Halley was considered one of the more open-minded members of the longitude panel and was impressed by Harrison’s ideas and drawings for a sea clock.
He knew, however, the Prize Board favored an astronomical solution, so he put Harrison in touch with England’s preeminent watchmaker George Graham to obtain an honest assessment of the concept. Graham quickly agreed to become Harrison’s patron and provided funding for a prototype that took five years to perfect.
Harrison presented his clock to the Board in London in 1736. He called it the H-1. In an unexpected move, he spent most of his time before the Board talking about plans to improve it and make it smaller. Impressed, the Board offered Harrison some money to support his next iteration.
Five years later, Harrison returned with the H-2 and again petitioned successfully for additional funds to create an even better clock and then disappeared for nearly 20 years. The Board granted him extensions and additional payments during this time.
While Harrison tinkered, other men aggressively pursued the prize money. In 1731, Englishman John Hadley and American Thomas Godfrey independently designed prototype inventions to measure longitude via the moon and stars. These inventions became known as the quadrant, which quickly evolved into a second-generation instrument called a sextant. With its mirrors and artificial horizon, a navigator could measure distances at night using the light of the moon. Then he would consult detailed lunar charts to compare distances between the moon and stars for various hours of the night in different geographies. It was time consuming, very complicated and relied upon charts that at the time weren’t fully completed.
John Harrison presented his third sea clock to the Board in 1755. Named H-3, this version measured 2’ high x 1’ wide and weighed 60 pounds. The big innovation in H-3 was a bi-metallic (brass and steel) strip mounted inside near the clock balances to keep it more immune to temperature changes. The Board couldn’t arrange a test at sea, however, because England was at war with France.
By the time a sea trial could be scheduled four years later, the never- satisfied Harrison had re-appeared with yet another clock. This one, the H-4, was radically different than its predecessors. It was a pocket watch. At five inches in diameter and a weight of three pounds, it contained all the parts and innovations from his clocks but replicated in miniature and constructed of silver, rubies and diamonds instead of wood. It dazzled some but not all the Board members.
The Board requested two sea trials of the longitude pocket watch – one successful and one questionable but conducted by a known skeptic – and still refused to declare Harrison the winner of the prize. Some historians believe the Board still disapproved of the clock and kept delaying an award so proponents of the lunar method would have more time to prove their method.
In 1772, the Prize Board begrudgingly recognized two longitude solutions but claimed neither were practical – a single pocket watch was insufficient for a whole nation, and the lunar method required many hours of complex calculations. Again, the Board delayed giving any prize awards.
It took pressure from England’s King George III on behalf of Harrison before the Longitude Board finally awarded him half of the £20,000 first prize in 1773, recognizing his long-term commitment to the challenge. He received more award money than any other competitor.
John Harrison died in 1776 at about the age of 83, but his longitude watch lived on, inspiring other inventors to create the next generation of marine clocks that came to be called chronometers. Even so, it took technology decades to catch up with demand. The British Navy finally began to supply its ships with chronometers in 1820, a development that helped the nation achieve hegemony at sea. American companies began mass producing chronometers in the 20th century to meet military needs in World War II.
Though eventually replaced by GPS, chronometers are still around today, produced mainly by watchmakers as expensive status items. And Harrison’s magnificent clocks? They’re housed behind glass in the Time & Longitude Gallery of the Royal Museums in Greenwich, England. You can, however, purchase a working replica of Harrison’s H-4 pocket watch at the museum shop should you wish to own a bit of maritime history.
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