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The History of Ships Clocks

Antique chart

It was the ship's clock that opened up the doors to accurate and safe navigation via longitude.

If you've ever been out to sea at night, looking around at nothing but pure blackness to every side, perhaps you can understand how daunting it must have been to navigate ships across the world's oceans in a time without computers and GPS functionality, let alone more basic gadgets and technologies. Surely, wise captains and seaman could navigate with the help of the North Star and various other constellations, and other innovations became prominent as well for gauging location, speed, distance traveled and more.

Navigation with Ships Clocks

But of course more precision was needed, and such new methods and systems became prominently used as well. In fact, it was the ship's clock that allowed great detail for navigation, opening up the doors to accurate and safe navigation via longitude. It was no matter of small importance either, in 1714 British government offered a prize of 20,000 pounds to whoever could accurately reveal longitude within a ½ degree while at sea. It's an amount that would be worth over $4.5 million in today's dollars.

Longitude could be measured by having two clocks, one set to the time at your home port and one set to the current time of the ship. The time difference could then be converted to distance traveled. The earth rotates completely, or 360 degrees, once every 24 hours, which means that each hour apart represents 15 degrees distance. The problem was that various factors at sea contrived to ruin these calculations, from temperature and pressure changes to location on the globe and more.

The solution was to use a precise clock that operated without a pendulum, to keep more consistent and precise time while at sea. It was the first true chronometer and it enabled vastly improved navigation and safety. Created and fine-tuned by John Harrison, it took a lifetime of work and achievement to produce a satisfactory result. For the record, he never won his official prize money but he did receive other payments for his work throughout the year that contributed to a substantial income.

Why Do Ship's Bells Ring on a 4 Hour Schedule?

Another interesting piece of information regarding the history of ships clocks is the answer to the above question, why do the bells of a ship ring on a four hour schedule? The four hours were used to keep track of the standard four-hour shifts for the crew. Using a simple sandglass to demarcate 30 minutes at a time, an eight bell system was derived to keep easy track of time throughout the day.

When the first half-hour passed, one bell rang. At each subsequent half-hour, an additional bell rang until you reached eight, which was a total of four hours, marking the end of the shift and the beginning of the next shift. At the next half an hour, the cycle would repeat. This system allowed the crew to easily note how long until the end of their shift, for those currently on duty, or how long until their shift began, for those going on duty the next shift.

There's a lot to learn about the history of ships and the history of ships clocks. The innovations that were developed came from necessity, and today are continued on as tradition. In a computer, GPS and digital free world, one could imagine the advantages of the onboard chronometer, and the easy to remember eight-bell, four hour system.


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