Marine Chronometers

Marine Chronometers


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What is a Chronometer?

Chronometer is a widely used term that usually fits one or more of the following definitions.


1. A precise clock


2. A timepiece which has met a set of requirements for accuracy in various temperatures and conditions set forth by a regulating institution such as a U.S. Naval Observatory


3. A clock with a chronometer escapement which is a spring detent.



What is a Marine Chronometer?


Marine Chronometers are highly accurate clocks kept aboard ships to aid in navigation. The chronometer is set to Greenwich time. When the time of this clock is compared with the local time at sea, a ship's navigator can determine the longitude at that position. As a result, it is important that such clocks keep accurate time amid variations in temperature, humidity and the motions of the sea.



Harrison's Legacy 


John Harrison, inventor of the marine chronometer, had advanced a practical method of finding longitude in 1759. His successors faced the challenge of making his complex and delicate design readily reproducible and affordable.

During the mid to late 1700s, many innovative individuals were making chronometers, including Thomas Mudge, John Arnold, and Thomas Earnshaw in England, and Pierre Le Roy and Ferdinand Berthoud in France.

Benefiting from technical improvements like the detent escapement and the temperature-compensated balance wheel, a simplified version of H-4, Harrison's original design, would remain the basis of chronometer design.

Armold and Earnshaw were the first to show that quality sea clocks could be produced in quantity. By the end of the 18th century, standard movements were being produced by cottage industry methods in England. Meanwhile, French chronometer making followed more traditional lines of individual craftsmanship, with each maker turning out a limited number of innovative hand-finished clocks. This French reluctance to adopt modern production methods allowed England to emerge as the chronometer capital of the world.

The demand for chronometers fell off as the age of exploration drew to a close, but was temporarily revived by the need for navigational instruments during both World Wars. However, the rise of alternative methods of navigation based on radio and radar eclipsed the chronometer. It must be noted that although considered a secondary means of navigation today, the chronometer is the only navigational method that is completely self-reliant. In the event of downed power sources, loss of radio communications, or satellite malfunction, the chronometer remains a reliable means of navigating the seas.