Page:Dictionary of National Biography volume 25.djvu/41

 Thomas Ellison, who was appointed. Harrison resided at Ashton until the Oxford Act was passed, when for a time he removed to Salford, eventually returning to Ashton, where he died on 31 Dec. 1670, aged 57. In his latter days he suffered severely from rheumatism, by which he lost the use of his limbs. He had been a strong, healthy man, ‘yet by his excessive studies, and assiduous labours and watchings, and sitting so close without fire in cold winter nights, his sinews became so contracted and his body so weak, that some years before he died he could not stir hand or foot; yet he was hearty and would often say, “If I were in the pulpit I should be well”’ (, Whole Works, i. 537). He was buried in the chancel of Ashton-under-Lyne Church, and his funeral sermon was preached by his successor, Ellison, who, as Calamy says, ‘gave him a great character, but not beyond his desert.’ His younger brother, Peter Harrison, D. D. (d. 1673), was rector of Cheadle, Cheshire, and conformed at the Restoration. Another brother, Jeremiah, was lieutenant-colonel in the army of the Commonwealth. 

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