John Harrison ( – 24 March 1776) was an English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of calculating longitude while at sea.
Harrison's solution revolutionized navigation and greatly increased the safety of long-distance sea travel. The problem he solved had been considered so important following the Scilly naval disaster of 1707 that the British Parliament was offering financial rewards of up to £20,000 (equivalent to £ in ) under the 1714 Longitude Act, though Harrison was never fully able to receive these rewards due to political rivalries.
Harrison presented his first design in 1730, and worked over many years on improved designs, making several advances in time-keeping technology, finally turning to what were called sea watches. Harrison gained support from the Longitude Board in building and testing his designs. Toward the end of his life, he received recognition and a reward from Parliament. Harrison ca