This two-day marine chronometer sits within a brass bound mahogany case with original key. It is very rare to find Charles Frodsham signed chronometers, and his instruments are highly sought after by collectors. This example is particularly fine and in good condition.
The movement has an Earnshaw spring detent escapement, compensation balance Poole's auxiliary, blued steel helical spring, free sprung, silvered dial with Roman numerals and subsidiary dials for the seconds and up and down. The signature of Charles Frodsham including his location on 84 Strand, London is on both the face and on a bone medallion set into the case, as is the number, 2716. Also featured is the broad arrow mark of the British Admiralty.
The inaccuracy of dead reckoning became apparent as soon as navigators ventured far out to sea. Countless methods of measuring longitudes were proposed. The simplest all used the same fundamental principle- compare the local sun time at a given instant with the time at the prime meridian for the same instant- the distance would give the longitude.
Local sun time could be obtained through observation of the sun with reasonable accuracy, at least at midday, but that left the problem of knowing the exact equivalent time at the prime meridian. A timepiece was required that kept exceptionally accurate time and was not affected by the motion of a ship or changes in pressure, temperature or humidity.
The first effective marine chronometer was John Harrison's clock #4, successfully tested in 1762. A copy of that clock accompanied James Cook on his 1772 and 1776 voyages. Records indicate that this particular Frodsham marine chronometer served aboard Royal Naval vessels from 1855 through May of 1932.
