John Harrison Clocks and Biography
John Harrison, born near Pontefract, Yorkshire, in 1693, was another man whose inventions advanced the science of chronometry. He was never enrolled in the Clockmakers' Company, but, having a mechanical bent, and his father's trade being carpentry, he gradually turned his attention to the casing and making of clocks.
By 1726 he had made two clocks, chiefly of wood, in one of which he had placed a "gridiron" pendulum of his own invention. So carefully made and delicately adjusted was this timekeeper that a contemporary writes of it that "it did not err a second in a month". In 1713 a reward of £20,000 was offered to anyone who could discover a method of ascertaining longitude at sea. John Harrison came to London in 1728 with drawings of an instrument for the purpose, but was advised to make the instrument before applying to the Commission. He returned again to Lon- don in 1735, and his instrument was of sufficient accuracy to cause the Commission to give him £500, and encourage him to proceed.
He made a second instrument in 1739, and a third in 1749, and finally, in 1773, the last half of £20,000 were paid him, for the Board of Longitude had in 1765 determined that the performance of Harrison's timekeeper had entitled him to the reward.
The fourth instrument was made in the form of a pocket watch about six inches in diameter. It was finished in 1759. Two trials of its accuracy were made, and on both voyages it corrected the longitude within the limits of the Act of 1713. He also invented the metallic compensation, a remontoir, and added a secondary spring as a substitute for the maintaining power during the time of winding up. He was engaged in the improvements of chronometrical mechanism during his sixty years of business life, and died in 1776, eighty-three years of age.