Longitude, METHODS

OF DETERMINING. Any proce by which the difference in the local time at two places can be found gives the difference of longitude. This may be done by transporting chronometers, by observation of the moon's position, by eclipses of the sun, moon, or Jupiter's satellites, or, best of all when practicable, by the electric telegraph. Till 1750 or later, no practical method was known for determining the longitude at sea. Navigators depended almost exclusively on their dead reckoning, which in case of long voyages was frequently in error by hundreds of miles. In 1714 a commi ion was appointed by the English government for the discovery of the longitude at sea. This commi ion continued in existence until 1828. Rewards of £10,000, £15,000, and £20,000 were offered for a practical method of determining the longitude within 60, 40 and 30 miles respectively. The maximum award of £20,000 was paid to John Harrison for improvements in chronometers (£10,000 in 1765, £10,000 in 1773). £3,000 was paid to the widow of Tobias Mayer for improved lunar tables. Smaller sums were awarded from time to time for encouragement of research and invention. In all the commi ion expended £101,000, much of which was wasted, as is usually the case with Government commi ions.