To obtain the ship's latitude with comparatively good results was an easy matter with the quadrant and its fore-runners, but the great problem for centuries was how to find the longitude, now universally and quickly obtained by the chronometer and simple observations in the morning or at noon. Spring clocks and watches appeared about 1530 but they were unreliable and of no use on long voyages. Sand glasses like those of the old Colonial churches were used on ships and so conservative is the British mind that some were in use on British naval vessels as late as 1828 and one authority states as late as 1839. Greenwich Observatory was established in 1675 and a Royal Commission was soon appointed with authority to award prizes for important inventions in aid of navigation. A prize of L20,000 was finally offered for a time-keeper that should meet certain requirements which practically meant absolute accuracy. In 1767, John Harrison produced the chronometer, based on the principle of an invention of 1735, and eventually he received the reward. Chronometers were so expensive and so hard to obtain that few New England ships had them until more than a half a century later. Other devices were tried to obtain longitude by lunar observations and by Jupiter's satellites, but these observations were too difficult to be of practical use. Today, fine watches serve for short trips and chronometers are carried by nearly all vessels making long voyages.

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