John Harrison (1693–1776)

HARRISON, JOHN (1693–1776), mechanician, born at Foulby, in the parish of Wragby, Yorkshire, and baptised on 31 March 1693, was the eldest son of Henry Harrison, by his wife Elizabeth Barber of Wragby. His father was carpenter and joiner to Sir Rowland Winn of Nostell Priory, and also repaired clocks. When seven years old John was taken by his father to Barrow-upon-Humber, Lincolnshire, where Winn had another estate. In childhood he was especially attracted by machinery on wheels. He received a scanty education, and was never able to express his ideas clearly in writing. A clergyman lent him a manuscript copy of Nicholas Saunderson's lectures on natural philosophy, which he copied with all the diagrams. In course of time he joined his father in the workshop, and occasionally made a little money by land-measuring and surveying. He tried to improve the construction of clocks and watches. In 1715 he constructed an eight-day clock with wheels made entirely of wood, which is still in going order at the Museum of Patents, South Kensington. To prevent the effects of heat and cold upon timekeepers, he devised in 1726 his ‘gridiron pendulum,’ which consists in having the bob suspended by a series of parallel rods, alternately of steel and brass, so arranged that the downward expansion of the steel rods from change of temperature is exactly compensated for by the upward expansion of the brass rods. This principle of compensation is now generally adopted. Two of Harrison's long eight-day clocks, one of them with the gridiron pendulum attached, are preserved in the museum of the Company of Clockmakers in the Guildhall, London. Another of his ingenious improvements in clockmaking was his recoil escapement, which obviated the necessity of keeping the pallets well oiled. This escapement has been found somewhat too delicate to be generally adopted. Harrison was also the first to employ the ‘going ratchet,’ or secondary spring, an arrangement for keeping the timepiece going at its usual rate while being wound up.

In 1713 an act was passed (12 Anne, cap. 15) offering rewards of 10,000l., 15,000l., and 20,000l. to any one who could discover a method of determining the longitude at sea within sixty, forty, and thirty geographical miles respectively. Harrison came to London in 1728 with drawings of an instrument for the purpose. George Graham [q. v.], who examined his invention, advised him to construct the instrument before applying to the board of longitude. He finished one in 1735, and having obtained certificates of its excellence from Halley, Graham, and others, he was sent in 1736 in a king's ship to Lisbon and back to test it. In this voyage he corrected an error in the ship's reckoning of one degree and a half. Six days after his return, on 30 June 1737, the board ordered 500l. to be paid to him in two moieties, though Graham, who was consulted, urged that he should have at least 1,000l. Harrison completed a second chronometer in 1739. It was less cumbrous than the first. For a third instrument of still smaller make he was awarded the Copley medal of the Royal Society in 1749. A fourth timepiece in the form of a pocket watch, about five inches in diameter, was finished in 1759. Trial of its accuracy was made by his son William during a voyage from Portsmouth to Jamaica and back, lasting from 18 Nov. 1761 to 26 March 1762, when it was found to have erred not more than one minute and fifty-four and a half seconds. This amounted to only eighteen geographical miles. The board of longitude, however, refused to certify that Harrison had won the prize. Harrison thereupon petitioned parliament, with the result that an act was passed authorising him to receive 5,000l. as part of the reward. The board merely paid him a further sum on account. On 28 March 1764 William Harrison sailed with the timekeeper for Barbadoes. He returned in about four months, during which time the instrument had determined the longitude within ten miles, or one-third of the required geographical distance. Still the board withheld their certificate, though they admitted that Harrison was entitled to be paid the full reward. A new act of parliament (5 Geo. III, cap. 20) awarded him, on condition of his giving a full explanation of the principles of his timekeeper, the payment of such a sum as with the 2,500l. he had already received would make one half of the reward; and the remaining half was to be paid when chronometers had been made after his design by other artists, and their efficiency fully proved. Harrison explained the construction of his chronometer on 22 Aug. 1765 in the presence of the astronomer-royal (Nevil Maskelyne) and six experts appointed by the board. An exact copy of his last watch was made by Larcum Kendal, and used by Captain Cook in his three years' circumnavigation of the world. Harrison's claims, however, were still unsatisfied. His watch was subjected to what he considered many more frivolous trials. He charged Maskelyne with being too much interested in endeavouring to find the longitude by lunar tables to regard his invention with favour. He even constructed a fifth watch, which, on the application of his son to Dr. Demainbury, was lodged in 1772 in the king's private observatory at Richmond. After ten weeks' trial it was found to have erred only four and a half seconds. The king now interposed in Harrison's behalf, but it was not until 14 June 1773 that parliament granted him the remaining amount of the reward, 8,570l. Harrison's four chronometers are preserved at the Royal Observatory, Greenwich. The success of the instrument was owing to the application of a self-compensating piece of mechanism to the balance-wheel, which contrivance, according to his provincial dialect, he called a ‘knib,’ but it is now termed the compensation-curb. Harrison died in Red Lion Square, London, on 24 March 1776, and was buried in a vault on the south side of Hampstead Church. A tomb in the churchyard was erected some years afterwards by his son, William Harrison, F.R.S. (d. 1815), and was reconstructed in 1879 at the expense of the London Company of Clockmakers. Harrison was not a member of the company. His wife Elizabeth died on 5 March 1777, aged 72. He had a musical ear, and made experiments on sound with a curious monochord of his own invention, from which he constructed a new musical scale or mechanical division of the octave, according to the proportion which the radius and diameter of a circle have respectively to the circumference. His writings are: 1. ‘An Account of the Proceedings in order to the discovery of the Longitude’ [anon.], 1763. 2. ‘A Narrative of the Proceedings relative to the discovery of the Longitude at sea … by J. Harrison's Timekeeper, subsequent to those published in 1763,’ 1765. 3. ‘The Principles of Mr. Harrison's Timekeeper, with plates of the same; published by order of the Commissioners of Longitude,’ 1767. The preface and the chapter entitled ‘Notes taken at the Discovery of Mr. Harrison's Timekeeper,’ are written by Nevil Maskelyne. 4. ‘Remarks on a Pamphlet lately published by Mr. Maskelyne under the authority of the Board of Longitude,’ 1767. 5. ‘A Description concerning such mechanism as will afford a nice or true mensuration of time, together with some Accounts of the attempts for the Discovery of the Longitude by the Moon; as also an Account of the Discovery of the Scale of Music,’ 1775. An engraved portrait of ‘Longitude Harrison,’ as he was called, accompanies a memoir in the ‘European Magazine’ for October 1789, the artist being B. Reading. His portrait also appears in Knight's ‘Portrait Gallery,’ from an engraving by P. L. Tassaert published in 1768 after a painting by T. King.

G. G.