Harrison, John (1693-1776)
English clockmaker and carpenter
John Harrison solved the so-called "longitude problem," that is, he developed the means to enable navigators to calculate their east-west (longitudinal) positions at sea. A ship's north-south (latitudinal) position is easily computed from the Sun, stars, date, and local time, but to calculate longitudinal position a navigator must also know the current time at the home port and compare it with the local time of the ship as determined by observing the Sun and stars. This calculation is based on the fact that every hour represents 15 degrees of longitude. The principle was known centuries before Harrison, but using it was not possible in practical navigation until he invented his portable, durable, and extremely accurate clock, which proved reliable under the harsh conditions of the sea.
Born the son of a carpenter on March 24, 1693, in Foulby, Yorkshire, England, Harrison early learned his father's trade as well as surveying, clockmaking, bell tuning, and several other practical skills. He also enjoyed music and was a singer. The family moved to Barrow-on-Humber, Lincolnshire, while Harrison was still a child. In the 1720s, he began a professional association with his brother James, born in 1704. Together until 1739, they designed and built beautiful, precise, reliable clocks, soon renowned as the most accurate in Britain.
As the world's dominant sea power from the end of the sixteenth century until the middle of the nineteenth, Britain was keenly aware of the longitude problem and was quite serious about solving it. In 1675, King Charles II founded the Royal Observatory at Greenwich, England, mainly to gather data for the longitude problem. In 1714, the British Parliament passed the Queen Anne Act, which offered a prize of £20,000 (about £1,932,917 in 2001 British money or $2,811,860 in 2001 American money) to anyone who could calculate a ship's longitude to within a half-degree throughout its voyage from Britain to the West Indies. Many tried and failed to win that prize.
Fixed on winning the prize, Harrison began working on the longitude problem in 1730 and submitted his first sea clock, known as the H1 chronometer, to the Board of Longitude in London in 1736. On the basis of H1's partial success, the Board gave him financial assistance to continue his research. From 1737 to 1740, he worked on a larger instrument, H2, but it failed. His experiments with H3 from 1740 to 1749 also ended in failure. In 1755, he stumbled across an entirely different design for H4, similar to a pocket watch. The test results of H4 on the voyage of the Deptford to Jamaica in 1761–62 and on the voyage of the Tartar to Barbados in 1764 exceeded the stipulations of the Queen Anne Act.
Despite the success of H4, the Board of Longitude awarded Harrison only £10,000. The Royal Astronomer Nevel Maskelyne (1732–1811), even though he was aboard the Tartar during the trial of H4, remained unconvinced that any timepiece could be a more accurate indicator of longitude than the popular "lunar distance method," by which navigators computed longitude from their observations of the Moon's position relative to selected stars, according to tables prepared by the Royal Observatory. Maskelyne was jealous of Harrison, whom he spurned as a mere "mechanic," and changed the rules of the contest to favor astronomers.
Harrison, with his son William, spent the rest of his life trying to claim the second half of his prize. The Board was adamant about not giving it to him but, in 1773, after Harrison appealed to King George III, Parliament grudgingly recognized his having solved the longitude problem and gave him an additional £8,750. All four of his marine chronometers are now in the National Maritime Museum, London. He died in London on his birthday in 1776.
History of Exploration Ii (Age of Exploration); Latitude and Longitude; Time Zones
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