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The Origins of... - The Origins of the Marine Chronometer

The Origins of... The Origins of the Marine Chronometer

The marine chronometer is a rather mysterious instrument that, before the arrival of the GPS, was an essential tool for navigators. But what was it used for exactly?

This special kind of timekeeper allowed sailors to the take the time from the port of departure with them to sea and use it to determine their longitude. Marine chronometers were able to maintain chronometric accuracy even under the strongest rolling and pitching of the high seas (something that was impossible with a pendulum clock) and allow the captain to know his position in the middle of the ocean, without having to keep land in view to locate himself and his vessel. Its inventor is none other than the famous British watchmaker John Harrison, who was a cabinet maker by trade with a secret love for watchmaking, which he taught himself in his spare time. 

The Marine Chronometer

Chronomètre de Marine © Ferdinand Berthoud

In 1714, the British government published the “Longitude Act”. This was an act of parliament that promised a prize of £20,000 to anyone who could make a device that could determine longitude at sea in a simple and reliable way. Today, this sum would be equivalent to several million dollars! On hearing of this prize, John Harrison began to imagine and design several clocks with different mechanisms that allowed, with varying levels of success, to maintain the accuracy of time on a moving ship. It took him several trials and prototypes to design a reliable enough timepiece and win the Longitude Act prize. 

Thanks to his marine chronometer, the British Empire was able to stay one step ahead of other navies thanks to this ability to determine its position at sea and therefore reign supreme over other navies for many years. 

The Marine Chronometer

Chronomètre de Marine © Ulysse Nardin

How did seafarers calculate longitude with their new clock? They calculated the time difference between a reference meridian and the true solar time of the place where they were located. Each hour difference was equivalent to an angle of five degrees. Thus, on a world map showing the 24 different time zones, each time zone represented 15 degrees (360 divided by 24 = 15).

This was not only useful on sea, but also on land as the marine chronometer allowed anyone in possession of one to calculate their exact location, thus allowing cartographers to create even more precise maps than ever before. Today, the marine chronometer still has its place in the most luxurious ships, even if they are no longer used for sailing. They are magnificent technical objects that bear witness to another time. 

The Marine Chronometer

Chronomètres FB-RSM © Ferdinand Berthoud

In the watchmaking world that we know so well, a number of brands have a strong link to this marine chronometer past, such as Ferdinand Berthoud, Ulysse Nardin, and Breguet to name a few. Some of them even have models that are directly inspired by these same historical marine chronometers that have marked horological history as we know it. 

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