John Harrison’s chronometer, or timepiece, was used to make the first accurate measurement of longitude at sea, revolutionizing ocean exploration and travel. His invention opened new vistas in cartography, astronomy, world commerce, and international timekeeping, and furthered colonialism and imperialism.

The British parliament established the Longitude Act Longitude Act (1714) in 1714 to encourage a solution to a problem that had vexed mariners, merchants, and governments for hundreds of years. The problem was the inability to measure longitude accurately, especially at sea. [kw]Quest for Longitude (1714-1762)
[kw]Longitude, Quest for (1714-1762)
Longitude at sea
Navigation;and longitude[longitude]
[g]England;1714-1762: Quest for Longitude[0440]
[c]Science and technology;1714-1762: Quest for Longitude[0440]
[c]Exploration and discovery;1714-1762: Quest for Longitude[0440]
[c]Mathematics;1714-1762: Quest for Longitude[0440]
Harrison, John
Halley, Edmond
Graham, George
Harrison, William

The concepts of latitude and longitude go back as far as the recognition of Earth’s generally spherical shape. Latitude lines—the virtual, horizontal lines that parallel the equator Equator and measure degrees north or south of the equator—had long since ceased to be a mystery. By the time of Christopher Columbus, Columbus, Christopher mariners had learned that by studying the elevation of the Sun above the horizon and by observing certain “fixed” stars, they could rather easily follow an east-west path corresponding to a latitude line.

For Columbus to measure longitude—that is, distance along any latitude line he was traveling—the element of time Time and navigation
Navigation;and time[time] came into play. One hour, one twenty-fourth of a day, corresponds to fifteen degrees of longitude east or west from a point of reference on an imaginary circumferential line through the poles and intersecting the equator. This reference line is called the prime meridian. Prime meridian It can be any longitude line; in modern times the line passing through Greenwich, England, Greenwich, England has come to be utilized as the prime meridian. For Columbus to convert that fifteen degrees into geographical distance, he needed to know not just what time it was aboard the Santa Maria but what time was being registered at the same moment in some place of known longitude. Because he had no timepiece (called a chronometer Chronometers beginning in the early eighteenth century) capable of this feat, he could not know the distance to India or any other landmass.

Although navigators and cartographers had most to gain from the solution of the longitude problem, and although it also attracted the attention of learned astronomers, it is not surprising, at least in retrospect, that a clock maker solved the problem. John Harrison, who was born in Yorkshire in 1693 but grew up in Barrow, Lincolnshire, made his first pendulum clock in 1713, just one year before the Longitude Act established a reward of £20,000 to the person who could devise a solution to the puzzle. Specifically, the invention had to prove accurate to within one-half of one degree of longitude on a trip from Great Britain to a port in the West Indies. The need for and the difficulty of the task are evident when one realizes that over this distance, an error of one-half degree would result in an error of several nautical miles, not a small error.

Not until 1728, however, did Harrison begin his pursuit of the great prize. In the meantime he concentrated on improving pendulum clocks. Pendulum clocks
Clocks Since all metals expand in heat, metal pendulums grow longer and measure time more slowly in hot weather. Harrison overcame this problem by combining long and short strips of two different metals in one pendulum. He also invented a device that virtually eliminated friction from the escapement—that part of the clock that regulates the motion of the wheelwork. Working with his younger brother James and with inexpensive materials (he could not afford better), he made clocks of amazing precision, accurate to within a second a month.

He entered the competition knowing that no pendulum clock would work on a sailing ship at sea, so he experimented on a mechanism that might be expected to withstand the movement caused by ocean waves. By 1730, armed with drawings of a sea clock, Sea clocks he went to London and called upon the great astronomer Edmond Halley. Knowing that the device of a clock maker probably would not impress a longitude board likely inclined to favor the ideas of learned astronomers and mathematicians, Halley sent Harrison to George Graham, a respected maker of watches and scientific instruments.

Encouraged by Graham, Harrison spent the next five years constructing his first sea clock. Now called H-1, it was a seventy-five-pound contraption with two large brass balances, connected by wires, taking the place of a pendulum. Tested on a sea voyage to Lisbon, it performed well enough to convince Harrison that he was on the right track.

During the next twenty-five years, Harrison strove for a smaller, lighter, and less complex chronometer, and in 1761 he completed H-4. By this time he was sixty-eight years old, but he had the assistance of his son William. William was born about the time the project began, but he grew into an able clock maker under his father’s tutelage. It was William who made the sea journey to Jamaica to test his father’s latest timepiece. The H-4 did not bear much resemblance to the first three versions; it looked like a somewhat oversized pocket watch, twelve centimeters (about five inches) in diameter.

William and the chronometer sailed aboard a ship called the Deptford in November of 1761. Checked against the local longitude, which had been determined astronomically, H-4 proved to be only five seconds slow, a deviation of only 1.25 minutes of longitude. For the total trip the error in longitude was 28.5 minutes, probably because on the return trip, completed on January 19, 1762, the Deptford had encountered particularly stormy seas. However, H-4 had still come within the limit of one-half of one degree.

This trip should have marked the end of the story, but the Board of Longitude insisted on further inspections and tests of the chronometer. Other claimants, including a prestigious astronomer, James Bradley, Bradley, James who was originally a Harrison supporter, came forward. Harrison was granted only a partial reward, and not until 1773, when he was eighty years old, did he receive the full amount of the prize.

Recognition of his feat came slowly, but eventually he was acknowledged as the true inventor of the chronometer. A modern navigator, while being honored at a dinner, proposed a toast to Harrison’s memory, to the man who “started us on our trip.” That navigator was American astronaut Neil Armstrong. Although the more accurate modern marine chronometer is based on principles different from Harrison’s, Harrison proved that an instrument could be made to facilitate navigation into previously unknown waters.

The invention of an accurate chronometer led to the expansion of knowledge Geography;and measurement[measurement] of Earth’s great waters. Captain James Cook, the eighteenth century maritime explorer, benefited greatly from the chronometer. In addition to increasing geographical knowledge, the chronometer enabled those aboard ship to make timed observations of heavenly bodies while at sea. These observations furthered the work of astronomers, making possible a more complete understanding of the heavens as well as the Earth.

With the problem of longitude solved, mapmakers could accurately represent the configurations and relative positions of landmasses. Being lost at sea, the universal experience of mariners up to Harrison’s time, became rare. Cartographers Cartography could pinpoint small geographical hazards and thus refine nautical charts, forever changing the experience of mariners, who for centuries had been running aground with great loss of men, ships, and cargoes. Knowing distances between ports and being able to chart safe routes between them fostered maritime commerce. Of course, colonial and imperial ambitions also increased.

In the long run the mastery of longitude made possible the simplification and standardization of international timekeeping, although not until the International Meridian Conference Meridian Conference (1884) of 1884 did the nations of the world agree to designate the longitude line passing through the old Royal Observatory in Greenwich as the prime meridian. This allowed the “opposite,” 180-degree meridian in the Pacific Ocean to serve as the international date line.

• Andrewes, William J. H., ed. The Quest for Longitude: The Proceedings of the Longitude Symposium, Harvard University. Cambridge, Mass.: Collection of Historical Scientific Instruments, Harvard University, 1996. A lively collection of papers presented at a 1993 conference on the question of longitude that includes several chapters examining Harrison’s work. Includes maps, illustrations, a bibliography, and an index.
• Christianson, David. Timepieces: Masterpieces of Chronometry. New York: Firefly Books, 2002. Christianson provides an efficient assessment of the horological significance of Harrison’s invention.
• Dash, Joan. The Longitude Prize. New York: Farrar, Straus and Giroux, 2000. In this book written especially for young readers, Dash explores the story of Harrison’s quest to solve the longitude problem. Includes bibliographical references, an index, and illustrations.
• Howse, Derek. Greenwich Time and the Discovery of Longitude. New York: Oxford University Press, 1980. An extensive, if highly technical, discussion of longitude and the establishment of an internationally accepted prime meridian.
• Landes, Davis S. Revolution in Time: Clocks and the Making of the Modern World. Rev. ed. Cambridge, Mass.: Belknap Press, 2000. Contains a particularly good account of the longitude problem as faced by mariners before Harrison’s contributions.
• Quill, Humphrey. John Harrison: The Man Who Found Longitude. New York: Humanities Press, 1966. The earliest and still the most thorough book-length biography of Harrison.
• Sobel, Dava. Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. New York: Penguin Books, 1995. A short but engaging popular biography of John Harrison.
• Wilford, John Noble. The Mapmakers. New York: Knopf, 1981. A history of cartography showing, in chapter 8, how Harrison’s achievement furthered the arts of navigation and mapmaking.

Hadley Describes Atmospheric Circulation

Hume Publishes A Treatise of Human Nature

Mayer’s Lunar Tables Enable Mariners to Determine Longitude at Sea

Bougainville Circumnavigates the Globe

Voyages of Captain Cook

Lord Anson; Louis-Antoine de Bougainville; James Cook; George Vancouver. Longitude at sea
Navigation;and longitude[longitude]