The Watch That Conquered Longitude — How the Sea and the Railway Aligned the World's Time

Until now, the watch had been something like a plaything for the wealthy, a tool for ‘owning time.’ Yet it was neither the court nor the monastery that demanded the highest precision from a timepiece. It was the sea, and the age of the railway that would soon arrive. Out in the middle of the vast ocean, to know where on the earth you stood — the answer to that urgent question was, in fact, hidden inside a single accurate clock. By measuring the height of the stars or the sun, sailors could work out latitude, their position north and south. But the east–west position, that is, longitude alone, had stood for ages as a riddle beyond the reach of humankind. This episode is the story of an obscure craftsman who gave his life to that riddle, and of how the watch became a ‘common language of the world.‘

The riddle of longitude that the sea posed

In the age of sailing ships, knowing one’s position was a matter of life and death for sailors crossing the open ocean. Latitude could be found relatively easily by measuring the height of the sun or the North Star. Longitude, however, was an entirely different matter. Because the earth turns once a day, longitude translates directly into a ‘difference in time.’ If you knew the gap between the time at your point of departure and noon at the place where you now stood, you could calculate how far east or west you had traveled — the principle was simple. The problem was that, at the time, no clock existed anywhere that could keep the ‘time at the point of departure’ accurately for weeks on end aboard a pitching ship.

The price of not knowing longitude was far too great. Ships had no choice but to proceed by dead reckoning, a guess based on experience, and a mistaken position meant sailing straight toward unseen rocks. In 1707, a British fleet ran aground off the Isles of Scilly, and the disaster — in which thousands of officers and men are said to have vanished into the sea — has been handed down as a symbol of that terror. How many lives an error of position could take — the sea kept posing that unanswered question to people.

In the face of this crisis, the state moved. In 1714 Britain enacted the Longitude Act, offering an extraordinary prize of up to 20,000 pounds for a method of finding longitude at sea to a fixed degree of accuracy. A Board of Longitude was set up to judge the entries. By the common wisdom of the time, the answer was thought to lie in the night sky. If one observed the motions of the moon and stars with precision, the time could be deduced — astronomy, many scholars believed, was the royal road.

The obscure craftsman, John Harrison

There was a man who challenged that ‘royal road’ from an entirely different direction. His name was John Harrison. He was not a university-trained astronomer but a woodworking craftsman raised in the English countryside. Having taught himself the making of clocks, he concluded that the answer lay not in the stars but inside a machine. To build a clock that would never lose its accuracy, however much the ship pitched, however the metal expanded and contracted with heat and cold. If only that could be done, longitude would be solved — he staked his life on that single point.

Over the course of decades, Harrison built one prototype marine clock after another. A mechanism to cancel out the errors caused by changes in temperature, a design that ran without oil — his inventions overturned the conventional wisdom of clockmaking one after another. And around 1761 he completed not another of his large machines but a portable timepiece, like an enlarged pocket watch, commonly known as H4. This single device was put to a practical trial on a voyage to British Jamaica, and it is said to have shown only the slightest error after the long passage. He had produced a result not in theory but out on the sea.

Even so, Harrison’s path was not a smooth one. The Board was slow to acknowledge his achievement, and payment of the reward dragged on. By one account, there was friction with those who held astronomy in high regard. In the end, with the backing of King George III, Harrison is said to have received a reward for his long years of achievement in 1773 — but that was only after he had drawn near the end of his life. One craftsman’s obstinacy spent nearly his whole lifetime before it gave a single answer to the riddle of the sea. It should be noted that the circumstances and amount of the reward vary across the sources, and differing accounts are often set side by side.

The railway drew the world’s time into a single line

If the sea demanded an ‘accurate clock,’ it was the railway that, on land, forced the time itself into alignment. Before the railway appeared, the hour in each town followed its own local sun. Even if the moment of noon differed between an eastern town and a western one, no one was troubled at the pace of horse or foot. But once the railway appeared, carrying people and goods from town to town at tremendous speed, this ‘time that differed from town to town’ turned into a danger in itself. If departure and arrival times differed from place to place, timetables fell into confusion and the risk of collisions and missed connections grew.

So Britain’s Great Western Railway, around 1840, began an attempt to align the hours across its entire network into one. The standard it took was the time set by the observatory at Greenwich, the so-called Greenwich Mean Time. This is known as an early recorded example of bringing scattered local times into a single standard time. In time this ‘railway time’ spread to railways throughout Britain, and the time shown by the station clock overwrote the time of daily life in each locality. By one account, by the middle of the 19th century the great majority of Britain’s public clocks are said to have been aligned to Greenwich Mean Time.

The same current appeared all the more vividly in a country with a vast territory. In the United States, in 1883, the railway companies are said to have agreed among themselves and introduced, all at once, a system that divided the land into several standard time zones. On that day, noon came twice in any number of cities, and the anecdote that people reset the hands of their clocks to the new standard time has been handed down as ‘the day of two noons.’ It is also recorded that there were people who resented having the time of their familiar land rewritten for the convenience of the state and the railways.

And so, when the obsession with precision that the sea had nurtured joined with the idea of standard time that the railway had spread, the watch was no longer the possession of a few wealthy people but a foundation that moved society as a whole. Being accurate saved lives, supported the flow of goods, and connected people to one another. The watch had become a single language shared by the world. And this ‘accurate clock’ would move its home to an unexpected place in the next age. Leaving the cabin and the station house, from the bottom of the pocket up onto the wrists of people —.