H4 and the Longitude Prize

Some problems are not solved by the men who are asked to solve them. They are solved by a man nobody asked, working in a room nobody visits, on a principle nobody in authority believes can work. The Board of Longitude was constituted in 1714 to find the longitude by the stars; it was a Yorkshire carpenter, not an astronomer, who found it in a box.

THE CARPENTER OF BARROW

John Harrison was born in 1693 at Foulby in the West Riding, the son of a joiner, and learned wood the way other men learn prayer. He built his first long-case clock in 1713, at twenty, the wheels cut from oak and lignum vitae because brass cost money he did not have. The wood self-lubricated; the clock kept time. By 1722 he had built the turret clock at Brocklesby Park that has never needed oiling in three hundred years. Wood taught him what brass would later confirm: that friction is the enemy, that a mechanism must carry its own correction, that temperature is a thief.

The Longitude Act had passed in 1714, the year after his first clock. Twenty thousand pounds, the price of a small estate, for any man who could fix a ship's east-west position to half a degree on a voyage to the West Indies. The Board of Longitude, sitting in London, expected the answer to come from the Astronomer Royal, from the lunar tables, from the heavens. Harrison, in Barrow-upon-Humber, expected it to come from a wheel.

He brought H1 to London in 1735, a brass machine the size of a small cabinet, weighing seventy-five pounds, and the Royal Society endorsed it. Then H2. Then, for nineteen years, H3, which never satisfied him. And then, abandoning the cabinet for the pocket, the silver watch he called H4, finished in 1759 when he was sixty-six. Five inches across. Diamond pallets. A remontoire that rewound itself every seven and a half seconds. He had spent forty-six years on the question. He sent his son.

SPITHEAD, THE EIGHTEENTH OF NOVEMBER

Twenty past ten in the morning, and the autumn cold had settled into the timbers of HMS Deptford, fifty guns, fourth-rate, swinging at her cable off Portsmouth. William Harrison, thirty-three years old, came up the side with a mahogany box under his arm and the sealed instructions of the Board in his coat. The box held the watch. The watch held his father's life.

The cabin was small and the light was grey. He set the box on the table, unlocked it, and lifted out the silver case. The H4 was warm from being carried close to his body, as the workshop trials had taught him to carry it; cold was the killer of rate. He wound it, as he would wind it every morning of the voyage at the same hour, and he placed it in its gimballed cradle so the roll of the ship would not reach the balance. Outside the stern windows the rigging of the fleet stood black against a sky the colour of pewter. The wind held foul. They would not sail for a week.

THE SECOND BEFORE THE CABLE WAS SLIPPED

He had time, in those days at anchor, to think the thing through, and the thinking ran in one direction only. The Board did not want this watch to succeed. The Astronomer Royal, Nevil Maskelyne, was at that moment perfecting the lunar-distance method by which the longitude would be found from the angle between the moon and a fixed star, and the credit would go to Greenwich, where credit had always gone. A clock was a tradesman's answer. A clock was made by hands that smelled of oil. The men who would judge the H4 were men who had spent their lives certain that the heavens, not a Yorkshire carpenter, would speak the answer.

His father had told him the principle a hundred times, and William turned it over now as he watched the watch tick in its cradle: that the longitude is only time. That the earth turns fifteen degrees in an hour, and a ship at sea need only know what hour it is at Greenwich, and what hour it is where she stands, and the difference multiplied gives her place upon the globe. That every navigator in Europe knew this, and that none of them had a clock that would keep Greenwich time through a tropic squall and an Atlantic gale and the salt and the heave and the change from English damp to West Indian heat. His father had built that clock. It sat ticking on the table. The question of the voyage was not whether the principle was correct. The question was whether eighty-one days at sea would betray the metal.

William wound it once. He noted the rate. He locked the box. He had nothing else to do; the watch would do the work. A man may spend forty-six years on a problem and at the end the problem comes down to whether a wheel five inches across will hold its beat across an ocean. He went up on deck to watch the weather.

THE PASSAGE TO PORT ROYAL

The Deptford slipped her cable on the twenty-fifth of November and stood out from Spithead on a foul wind that softened only at the Bay of Biscay. William wound the watch each morning at the same hour. The ship's master kept the log. They made Madeira, and there William computed the longitude from the H4 and found it correct against the known position of the island within a mile and a half; the ship's master, who had bet against the watch in the Portsmouth taverns, said nothing. They stood west across the trade winds for fifty-three days. The weather turned warm. The bi-metallic strip in the watch, two metals brazed together so that heat bent one against the other and corrected the rate, did its quiet work. The remontoire rewound itself every seven and a half seconds, year in, year out, indifferent to the swell.

They raised the Blue Mountains of Jamaica on the eighteenth of January 1762 and dropped anchor at Port Royal the following day. Eighty-one days from Spithead. The Board's observers came aboard with their instruments and their tables. They compared the H4's reckoning of the longitude of Port Royal harbour to the astronomical longitude they themselves had established. The watch was one and a quarter miles east of the truth. The Act required thirty miles. The H4 had beaten the requirement by a factor of twenty-four.

THE BOARD AT THE ADMIRALTY

The Board of Longitude received the result in the spring of 1762 and did not pay. It had, the Commissioners said, been a single voyage, and a single voyage might be a fluke. A second trial was required. The H4 was sent again, to Barbados in 1764, with William once more its keeper, and on a hundred-and-fifty-six-day voyage it lost forty seconds, the equivalent of about ten miles of longitude, three times better than the Act required. The Board still did not pay in full. Now the objection was that John Harrison must surrender the H4 for dissection, must explain its mechanism to a committee of watchmakers, and must build a second working copy under inspection before the prize would be released. Each demand was met. Each demand was followed by another.

Eight thousand seven hundred and fifty pounds was paid in 1765. The remaining eleven thousand two hundred and fifty was withheld on a succession of technicalities for eight more years, while the Astronomer Royal published his lunar tables and the credit drifted, as the Board had always intended it should drift, toward Greenwich. Harrison was seventy-two, then seventy-five, then seventy-nine. He wrote letters. He built the H5 with his own hands.

In 1772 William Harrison was granted a private interview with George III at the Queen's House. The king, who had tested the H5 himself in the palace observatory and found it accurate to a third of a second a day, listened to the whole history of the Board's evasions and said, by William's own memoir of 1796, these people have been used very ill, and, by God, Harrison, I will see you righted. The king put the case to Parliament directly. In 1773 a Parliamentary grant of the remaining sum was voted, the wording carefully avoiding the word prize: a payment to John Harrison in recognition of his services in the discovery of the longitude. Harrison was eighty.

WHAT THE WATCH MADE

He died three years later, on the twenty-fourth of March 1776, his eighty-third birthday, in the house at Red Lion Square where the H4 had been built. He is buried at St John-at-Hampstead. By 1780 the marine chronometer was standard issue on Royal Navy capital ships. By 1815, after Trafalgar and the long blockade, no British ship of the line went to sea without one. By 1875 the P&O service was running to Australia by chronometer alone, the lunar-distance method retired to the textbooks. The empire that mapped the world mapped it on Harrison's wheel.

The end of the longitude problem was not announced by the Board that had been constituted to solve it. It was announced, quietly, by a watch ticking in a gimballed cradle in the cabin of a fourth-rate ship at Spithead, while a thirty-three-year-old man with his father's name watched the weather and waited for a foul wind to turn. At the Royal Observatory at Greenwich the H1, H2 and H3 are kept running to this day by the horological staff. The H4, since its bicentennial restoration in 1962, is kept still, the silver case open under glass, the diamond pallets motionless, the work done.