BERTHOUD, FERDINAND

born March 19, 1727, Plancemont, Switz. died June 20, 1807, Groslay, Fr. outstanding horologist and author of extensive treatises on timekeeping. Berthoud was apprenticed to his brother, a clockmaker at Plancemont, and he subsequently studied in Paris. His indefatigable inventiveness and many publications soon made him influential in horological circles, and he became involved in the attempt to solve the problem of determining longitude at sea. Berthoud's major achievement was his development of an accurate and practical marine clock, or chronometer. Such an instrument had previously been constructed in expensive and delicate prototypes by Pierre Leroy of France and John Harrison of England. Berthoud's improvements to the chronometer have been largely retained in present-day designs. He was succeeded in his work by his nephew Pierre-Louis Berthoud (17541813), a celebrated chronometer maker in his own right.