Marine Chronometer or "Longitude Clock" - Definition and History

A marine chronometer is a precise timekeeping device used in navigation to determine longitude and astronomical positions. Marine chronometers were first developed in 1759 by the English clockmaker John Harrison . In 1761, John Harrison won the 20,000 pound sterling prize offered by the British Parliament in 1741 for solving the longitude problem with the clock he developed.

This chronometer, called H.4, achieved an accuracy of 5.1 seconds on the voyage to Jamaica and back in five months in stormy seas. ^{[ 142 ] [ 143 ]} The Swiss watchmaker Louis Berthoud (1753–1813) manufactured a precision pocket chronometer , which Alexander von Humboldt tested on his sea voyages in 1799.

This marine chronometer made it possible to determine longitude very accurately. Humboldt was thus able to make precise descriptions of ocean currents and, by comparing these precise measurements with the ship's displacement, calculate their direction and strength.

Marine chronometers continued to be used in the navy even after World War II. The decline of chronometers only came in the second half of the 20th century with the invention of the quartz watch, whose accuracy improved by three orders of magnitude. This meant that there was no longer any need for chronometers as navigational instruments.