John Harrison

English engineer and clockmaker

• Born: March 1, 1693
• Birthplace: Foulby, Yorkshire, England
• Died: March 24, 1776
• Place of death: London, England

Harrison developed chronometers that could keep time at sea with sufficient accuracy to make reliable calculations of longitude at any point on the globe. This development revolutionized maritime navigation.

Primary fields: Maritime technology; navigation

Primary invention: Sea chronometers

Early Life

John Harrison was born in March, 1693, in the village of Foulby in Yorkshire, England. While he was still a young child, the Harrisons moved to Barrow-on-Humber in Lincolnshire, where John apprenticed with his father to become a carpenter. He married Elizabeth Barrel in 1718, and when she died in 1724 he remarried to Elizabeth Scott. Interested in mechanics from the time he was a teen, Harrison began constructing clocks by 1713. While carrying out his principal trade, for more than a decade Harrison and his younger brother James worked at perfecting an accurate regulator clock. Their partnership lasted nearly two decades.

Sometime after 1714, Harrison learned that an act of Parliament had established a prize of œ20,000 to be awarded to the first person who could develop an accurate method of determining longitude, the east-west position of an object on Earth. This calculation was especially important to ships, which had often missed ports of call or suffered tragedies because they could not determine accurately their location on the open oceans. The act creating the Longitude Prize also established a Board of Longitude to evaluate any proposal or machine submitted by claimants, and it specified terms for the award of any or all of the amount set aside by Parliament. Sometime during the 1720’s, Harrison decided to compete for the prize.

After a decade of experimentation, in 1730 Harrison published a lengthy treatise describing his method for crafting a “sea clock” for use in calculating longitude by comparing the local time to the time at a fixed point of departure. While the method made sense theoretically, few thought it possible to construct a device that would keep accurate time under the harsh conditions at sea. Harrison disagreed. He proposed an innovative design that reduced fluctuations due to friction, compensated for changes in temperature, and adjusted for fluctuations in the speed at which a clock might run when first wound or when in need of rewinding. Confident in his ability, in 1730 he applied to the Longitude Board for funds to construct his first sea clock. Some members were immediately interested, and they obtained financial support for him. Harrison spent the next five years building a machine that he could submit to the trials specified for earning the prize.

Life’s Work

Harrison’s challenge was significant. He was operating on the principle that longitude could be calculated by comparing the difference between local time and the time at the ship’s point of departure. Although local time could be measured at sea using astronomical readings, knowing the time at one’s departure point had always been difficult to determine because even the best timepieces lost seconds (sometimes minutes) each day. Errors of seconds or minutes could result in inaccuracies placing a ship many miles from its actual location. Therefore, the design of a clock that could withstand the rigors of sea travel and keep time with sufficient accuracy was key to solving the problems associated with determining longitude.

The first sea clock designed by Harrison with the assistance of his brother, designated H1 by later historians, was a bulky chronometer measuring three feet in height, width, and depth, consisting of various metals and wood. After inspection by members of the Royal Society of London, the country’s leading scientific organization, it was given a short sea trial to Lisbon, Portugal, in 1736. The terms of the act of Parliament establishing the prize, however, specified that the device must be proven accurate on a round-trip voyage to the West Indies. In 1737, the full Board of Longitude met to examine H1 and review results from the Lisbon voyage before authorizing the West Indies test. Curiously, rather than submit H1 to the West Indies voyage, Harrison indicated that he wished to construct a new clock for this test, and with the board’s financial support he began crafting H2, incorporating improvements of original concepts used to build H1. Two years later, Harrison decided to shelve H2 and begin work on H3. For the next nineteen years, he worked diligently on the project. During this time, he received small sums from the Longitude Board to underwrite his work. Additionally, even though none of Harrison’s clocks had yet been tested under the terms established for the award of the Longitude Prize, in 1749 Harrison’s accomplishments were celebrated publicly when the Royal Society presented him with the Copley Medal, its highest honor.

While Harrison was working to perfect H3, he was also experimenting with the design of watches. Although there were similarities between the two forms of timepieces, the construction of an accurate watch required even more skill. Harrison manufactured a pocket watch in 1753 and, perhaps encouraged by its accuracy, began constructing a larger one for use at sea. Harrison was now working closely with his son William, who eventually became his spokesperson and public champion. By 1760, Harrison had completed work on H3, which was scheduled to be tested on a voyage to the West Indies, but for some reason Harrison decided to submit to the Longitude Board his new watch, designated H4, for testing. Because he was too old for extended sea travel, Harrison sent William on the voyage to Jamaica, during which the watch proved remarkably accurate. Unfortunately, when the board met in 1762 to review the results, questions arose about testing procedures and Harrison was denied the prize. Instead, over the next several years the board established new criteria Harrison would have to meet in order to claim the œ20,000.

Harrison was furious, and he blamed his fate on machinations by certain board members, particularly Nevil Maskelyne, who in 1762 was working on an alternative method for calculating longitude using lunar charts, and who eventually assumed the influential post of astronomer royal. Maskelyne was not alone in expressing concern about Harrison’s work. Many board members were insistent that Harrison turn over all of his timepieces to them and agree to let others reproduce his chronometers so that the board could determine if his solution was practical. Harrison was hesitant to comply with these directives. By 1763, rivals began to emerge to compete for the prize, and he was concerned that his work might be pirated.

A second sea trial of H4 was authorized, and even though Maskelyne was heavily involved in it, the results were sufficiently promising for the board to award Harrison half the prize, indicating that he could qualify for the other half if the watch passed further tests—and if it could be shown that his chronometer was replicable. Harrison was not content with the decision, which he thought was politically motivated. After fighting for years to keep his designs secret, in 1767 he finally acquiesced to the board’s demands, turning over his four devices and his technical drawings to them. The board commissioned a rival watchmaker, Larcum Kendall, to construct a duplicate of H4. Further trials of Harrison’s watch were held at the Royal Observatory in Greenwich. Harrison was also instructed to make two duplicates, but he delayed that work for a variety of reasons, instead concentrating his efforts on construction of yet another timepiece, H5. By this time, King George III had begun to show a personal interest in Harrison’s work, and a test of the H5 was conducted at the king’s personal observatory in Richmond outside London.

While they continued wrangling with the Longitude Board, both John and William Harrison mounted a public campaign to gain the remainder of the prize money, lobbying Parliament for redress. In 1773, at the urging of the king, Parliament agreed to award Harrison œ8,750—not the full amount he had hoped for, but a sum that clearly indicated the nation’s gratitude for his accomplishments. Although Harrison felt only partially vindicated by this grant, he was finally satisfied that he was being recognized as the person who had solved “the longitude problem.” He died in 1776 before mass production of maritime chronometers based on his designs would revolutionize shipping throughout the world.

Impact

Harrison’s chronometers proved that it was possible to create a device that could keep time at sea with sufficient accuracy to make reliable calculations of longitude at any point on the globe. His combination of specially designed balances, his employment of a bimetallic strip to compensate for expansion of metals at different temperatures, and his development of a mechanism to ensure that time was kept accurately while his chronometers were being rewound were revolutionary ideas that paved the way for the production of chronometers that would allow ships to sail with greater assurance of their position.

The first real vindication for Harrison’s efforts was accomplished before he died. Captain James Cook departed England in 1772 for a South Seas voyage, taking along the copy of Harrison’s chronometer made by Kendall. As Cook reported, that device proved exceptionally valuable for determining longitude and charting the lands visited by him in his three-year cruise. While many improvements were made in the decades following Harrison’s death, several devices modeled on his designs were constructed for general use. Not only did these provide a means of calculating a ship’s position, but, as Cook had shown on his voyage, they also were instrumental in helping mariners revise charts of the ocean and its land masses, especially islands located at remote places around the world. As a consequence, the work Harrison did in developing his sea clocks paved the way for the expansion of both commercial trade and exploration that occurred during the nineteenth century and beyond.

Bibliography

Dash, Joan. The Longitude Prize. New York: Farrar, Straus and Giroux, 2000. Describes the efforts of the British government to solve problems associated with determining longitude and recounts Harrison’s various attempts to create a reliable instrument to measure longitude at sea. Targeted at students.

Quill, Humphrey. John Harrison: The Man Who Found Longitude. New York: Humanities Press, 1966. Detailed account of Harrison’s career, drawn from contemporary records, journals, and publications. Examines Harrison’s struggle to claim the Longitude Prize. Provides technical explanations for each of the chronometers Harrison created.

Sobel, Dava. Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time. Tenth anniversary edition. Foreword by Neil Armstrong. New York: Walker, 2005. Historical account of Harrison’s attempts to create a workable chronometer that could be used to calculate longitude; describes his struggles with the committee appointed by Parliament to award the British government’s Longitude Prize.