The document summarizes John Harrison's work to solve the longitude problem through the invention of the marine chronometer. It details Harrison's four clock designs (H1-H4) between 1730-1761, culminating in H4 accurately determining longitude on voyages to Jamaica and Barbados. However, the Board of Longitude and Astronomer Royal Nevil Maskelyne opposed Harrison's approach and favored lunar distance tables. After further trials, Parliament awarded Harrison financial compensation in 1773, recognizing his solution to the problem. The Board of Longitude was later abolished in 1828.