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.
Today, if you want accurate time today, pretty much anywhere in the world, you can get it. Even out at sea, you can rely on a decent quartz watch to be accurate to +/- 5 secs a month. A high-accuracy quartz can be even more accurate at +/-10 seconds a year. And modern sailing GPS systems there’s no need for an accurate watch. Navigating in the pre-GPS world, though, accuracy wasn’t a matter of watchnerdism, it was the difference between life and death.
For the men aboard four British warships, HMS Eagle, HMS. Association, HMS Romney and HMS Firebrand, the lack of accurate marine time meant their ships foundered and sank in October 1707. 2,000 men lost their lives partly because of vicious storms but, critically, because poor marine timekeeping meant they believed they were in safe waters when, in fact, they blindly ran onto rocks off the Isles of Scilly.
The need for an accurate marine timekeeper was acute.
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.
This rare, 65mm, water-resistant Ditisheim silver open-face keyless lever deck chronometer from 1920 is a beautiful example. It has a silvered matte dial, Roman numerals, blued steel spade hands, subsidiary seconds and outer railway minute divisions. It also has a 52 hour power reserve indicator, screw bezel and screw back, large ball-shaped crown Gilt-finished lever movement, 21 jewels and a Guillaume balance.
Paul Ditisheim was one of the leading lights in developing the new generation of chronometers, improving them significantly through his studies on the impact of atmospheric pressure and magnetic fields. In fact, thanks to his inventions, he was able to craft some of the most precise chronometers ever made.
In 1903, Ditisheim’s watches won awards at the Kew and Neuchatel Observatories’ and they went on in 1912, to win the world’s chronometric record at the Royal Observatory at Kew.
Many names we now know as wristwatch makers were also makers of marine chronometers. Stowa made Kriegsmarine chronometers and even Ulysse Nardin produced pieces like this 1941, 64mm keyless pocket chronometer. It also runs an accurate Guillaume balance and a 41-hour rotating power reserve indication.
Despite their phenomenal quality - and often equally remarkable state of condition - marine chronometers still fetch far less than many ‘collectable’ wristwatches. Even watches from makers like Mercer, Zenith and Hamilton can be had for comfortably less than $4,000. And, because relatively few collectors know and understand the significance of deck watches, there’s always the chance of picking up a bargain.