John Harrison, a most accurate mechanic; he was the inventor and maker of the famous timekeeper for ascertaining the longitude at sea, and also of the compound, or as it is commonly called, the gridiron pendulum; born at Foulby, near Pontefract, in Yorkshire, 1693; died 1776. He assisted in the profession of his father, which was that of a carpenter, and according to the miscellaneous practice of country artisans, surveying land and repairing clocks and watches. In 1726 he had constructed two clocks, mostly of wood, on which he applied the escapement and compound pendulum of his own invention. These surpassed everything then made, scarcely erring a second in a month. In 1735 he went to London with a machine for determining the longitude at sea, with which, by the Board of Longitude, he was sent to Lisbon for a trial of its properties. In this short voyage he corrected the dead reckoning about a degree and a half; a success that procured him both public and private encouragement. About 1739 he completed his second machine, of a construction much more simple that the former, and answering much better. His third machine, produced in 1749, was still less complicated than the second, and superior in accuracy, as erring only three or four seconds in a week. He afterwards made a fourth, with which his son make two voyages; the one to Jamaica, the other to Barbadoes, in both which experiments he corrected the longitude within the nearest limits required by the Act of the 12th Queen Anne, and the inventor thereof received the proposed reward of ₤20,000. The fourth machine, which is the timekeeper, has been copied by Mr. Kendal, and this copy, during a three years' voyage round the globe, in the southern hemisphere, with Captain Cook, answered as well as the original. The latter part of this life was employed in making a fifth timekeeper, on the same principle as the preceding one, which, at the end of a ten weeks' trial in 1772, in the King's private observatory at Richmond, erred only four seconds and half. In 1775 he published "A description concerning such mechanism as will afford a nice or true measurement of time, &c.," 8vo. This work also includes an account of his new musical scale. It will easily be supposed that, from Mr. Harrison's reclusive manner of living, he was not a man of the world, and that from his unacquaintance with letters he was little of a writer; yet, in conversing on his profession, he was clear, distinct, and modest. He resided in Red Lion Square, London, where he died, and his gravestone is in Hampstead Parish Churchyard.
