John Harrison

1693-1776

English Horologist

Perhaps the most famous clockmaker of all time, John Harrison solved the problem of reliably calculating a ship's longitude while at sea. By designing a highly accurate clock that allowed mariners to chart their position on Earth far more precisely, Harrison solved one of the most important scientific and technological problems of the eighteenth century.

John Harrison was the eldest of the five children of Henry and Elizabeth Harrison. He learned carpentry from his father and picked up excellent craftsmanship and a detailed knowledge of woods. John began building clocks quite early, enlisting his younger brother James to assist him. The first known Harrison clock dates from 1713, and the brothers built two more long case (grandfather) clocks in 1715 and 1717. How Harrison learned the complicated art of horology remains a mystery. At this time, clocks were very expensive and not particularly common, especially in isolated rural villages. No record exists of the young Harrison meeting with a clockmaker. Yet by 1720 he had built a clock for the tower of a local manor house. This clock elegantly employs Harrison's intimate knowledge of woods—the parts that would ordinarily need lubrication are crafted out of a tropical hardwood that naturally oozes its own oil.

In 1718 Harrison married Elizabeth Barrel. They had a son, also named John, in the summer of 1719. Elizabeth died in 1726, and John remarried within 6 months. He and his new wife (also named Elizabeth) spent the next 50 years together, producing two children: William in 1728, and a girl, again named Elizabeth, in 1732. While losing his first wife and remarrying, John had designed the two most accurate clocks in the world by 1727.

In 1714 the British Parliament established a 20,000-pound prize for any method or invention useful for accurately determining the longitude of a ship at sea. At the time, it seemed most likely that the solution to the "problem of longitude" would come from astronomy, and several scientists, including the Astronomer Royal, were named to the Board of Longitude as prize judges. By 1730 Harrison had traveled to London, met with a leading horologist, and obtained small grants to help him construct a seaworthy clock. Over the next 27 years, he built three large sea clocks, each weighing more than 60 pounds (27.2 kg).

Yet by the time the clock—called the H.3—was ready for testing in 1757, Harrison had imagined a radically new approach. Eschewing the hefty H.3, he designed a relatively tiny watch—just five inches (12.7 cm) across—endowed with an innovative new style of escapement. The H.4 proved as accurate as the H.3 and fit in a large pocket.

The H.4 cleanly passed the lengthy sea voyage stated as the test for the Longitude Prize. Surprised that a tinker's clock had passed the challenging test before an astronomical solution was discovered, the Board of Longitude then paid half of the 20,000-pound prize, but refused the other half until the watch passed a series of stringent, previously unstipulated, tests. Nevil Maskelyne (1732-1811), then both Astronomer Royal and a proponent of a competing astronomical solution, conducted these tests, which the watch, not surprisingly, failed. These new tests hounded Harrison until nearly the end of his life, ultimately denying him the full prize. A sympathetic King George III finally intervened on Harrison's behalf and Parliament made a special payment of more than 8,000 pounds in 1773.

John Harrison died three years later in 1776, a country carpenter who, despite active opposition from much of the scientific establishment, solved a key problem of eighteenth-century science and technology.

ROGER TURNER