Thursday 13 April 2023

Marine Chronometer sees safe passage


A Hamilton Lancaster P. A. Chronometer Deck watch sold £500 12th April 

The Deck Chronometer by Dan Henry.

For sailors, accurate time at sea is critical.  Because one hour corresponds to 15° of longitude, a navigator with an accurate timepiece can work out exactly where he is. And that makes the difference between sailing safely past hazards and not knowing what lurks beneath the surface.

Before the marine chronometer, mariners and watchmakers faced a dilemma.  Traditional pendulum clocks were incredibly accurate, but no use on a rolling sea.  Their pendulums and weights swing wildly even when the timepieces were mounted in gimbals.  At the same time, pocket watches (with their more stable spring-regulated oscillators) were relatively unaffected by the rolling of a ship, but the movements simply weren’t good enough to be accurate.  They certainly couldn’t be depended on to keep accurate time during a voyage that might last weeks or months.  And the more inaccurate the timepiece, the further a ship could be off-course without even realising

Developing an accurate marine chronometer was more of a challenge for watchmakers than producing complications like calendars, moon-phases or chronographs.  But, finally, from Harrison’s work in the early eighteenth century, they managed to develop ever more accurate marine chronometers.

These watches were much heavier and sturdier to survive life at sea and, critically, were far more accurate than an ordinary pocket watch. Until the 1940s, they were the most accurate portable watches in the world and the ‘tool watches’ of their day.

Marine (or deck) chronometers often look like oversized pocket watches and their silver cases are - unsurprisingly - much more resistant to water.  The last thing you want, in the middle of a storm, is for your main navigation device to fail because it’s got a bit damp.

For collectors, this central importance of deck chronometers to a safe passage means the watches are often superbly well-preserved.  Because they were obsessively taken care of by the Captain or master of the vessel, they seldom endured the knocks and bashes that saw off other watches.  And, as they were often fitted in gimballed, shock-protected wooden cases, their chances of survival were even better.

Ships’ masters and captains were obsessive about their chronometers, carrying them with them whenever they left the ship.  That meant not only were they very well looked after instruments indeed, but they were also much safer from interference.  Officers would set their own watches by the ship’s marine chronometer, so it provided a unified timing standard for the entire crew.

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