HARRISON, JOHN (16931776)

This article appears in Volume V13, Page 24 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: HAN-HEG

HARRISON, JOHN (16931776) , English horologist, was the son of a carpenter, and was born at Faulby, near Pontefract in Yorkshire, in the year 1693. Thence his father and family removed in 170o to Barrow in Lincolnshire.

Young

Harrison at first learned his father's trade, and worked at it for several years, at the same time occasionally making a little money by land-measuring and surveying. The bent of his mind, however, was towards mechanical pursuits. In 1715 he made a clock with wooden wheels, which is in the patent museum at

South

SOUTH
SOUTH, ROBERT (1634–1716)

Kensington, and in 1726 he devised his ingenious " gridiron pendulum," which maintains its length unaltered in spite of variations of temperature (see CLOCK). Another invention of his was a recoil clock escapement in which friction was reduced to a minimum, and he was the first to employ the commonly used and effective form of " going ratchet," which is a

spring

SPRING (from " to spring," " to leap or jump up," " burst out," O. Eng., springau, a common Teut. word, cf. Ger. springer, possibly allied to Gr. QnrFpxecOac, to move rapidly)

arrangement for keeping the timepiece going at its usual rate during the

interval

INTERVAL

of being wound up.
In Harrison's time the British government had become fully alive to the necessity of determining more accurately the longitude at sea. For this purpose they passed an act in 1713 offering rewards of 1o,000, 15,000 and 20,000 to any who should construct chronometers that would determine the longitude within 6o, 40 and 30 M. respectively. Harrison applied himself vigorously to the task, and in 1735 went to the Board of Longitude with a

watch

WATCH (in O. Eng. wcecce, a keeping guard or watching, from wacian, to guard, watch, wacan, to wake)

which he also showed to Edmund Halley, George Graham and others. Through their influence he was allowed to proceed in a king's ship to Lisbon to test it; and the result was so satisfactory that he was paid 500 to carry out further improvements. Harrison worked at the subject with the utmost perseverance, and, after making several watches, went up to London in 1761 with one which he considered almost perfect. His son William was sent on a voyage to Jamaica to test it; and, on his return to Portsmouth in 1762, it was found to have lost
only i minute 54z seconds. This was surprisingly accurate, as it determined the longitude within 18 m., and Harrison claimed the full reward of 20,000; but though from time to time he received sums on account, it was not till 1773 that he was paid in full. In these watches compensation for changes of temperature was applied for the first time by means of a " compensation-curb," designed to alter the effective length of the

balance

BALANCE (derived through the Fr. from the Late Lat. bilantia, an apparatus for weighing, from bi, two, and lanx, a dish or scale)

spring

SPRING (from " to spring," " to leap or jump up," " burst out," O. Eng., springau, a common Teut. word, cf. Ger. springer, possibly allied to Gr. QnrFpxecOac, to move rapidly)

in proportion to the expansion or contraction caused by variations of temperature. Harrison died in London on the 24th of

March

1776. His want of early education was felt by him greatly throughout life. He was unfortunately never able to express his ideas clearly in writing, although in conversation he could give a very precise and exact account of his many intricate mechanical contrivances.
Among his writings were a Description concerning such Mechanism as will afford a Nice or True Mensuration of Time (1775), and The Principles of Mr Harrison's Timekeeper, published by order of the Commissioners of Longitude (1767).

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