Collecting 101

1.

What is a marine chronometer?

A marine chronometer is a specialised clock, designed to be used onboard a ship to determine its position. The invention of the marine chronometer in the 18th century was a major technical accomplishment: for the first time, a ship’s longitude could be accurately measured, and navigational disasters averted. It proved an invaluable nautical tool and was adopted by seafarers around the globe. Marine chronometers are traditionally large items, with the precision timepiece set into a wooden case to protect it from knocks and damp during voyages.

2.

Invention

By the turn of the 18^th century, powerful countries were locked in a fierce competition for dominion over the seas. The pursuit of control over maritime routes was a perilous one: with no accurate method for measuring longitude, vessels were too often lost and wrecked. In 1707, the Royal Navy suffered the worst accident in maritime history, when four warships hit submerged rocks and two thousand sailors perished.

This tragedy was the catalyst for the invention of the marine chronometer. The British Government passed the Longitude at Sea Act in 1714, which offered £20,000 – a substantial reward – to any person who could discover a way to measure longitude with strict precision. It proved a formidable challenge, and while many great scientists of the day put their minds to the task, none could meet the demanded levels of accuracy.

Ultimately, it was not scientist, but a carpenter from Yorkshire who solved the problem. John Harrison began building his first prototype in 1728, then spent decades experimenting and developing different iterations, before he was finally awarded the prize. With his fourth model, the H4, Harrison introduced a bi-metal balance that could automatically adjust to fluctuating temperatures and maintain accuracy. This innovation proved to be a gamechanger. In 1761, the H4 was tested on a trans-Atlantic voyage and kept almost perfect time.

3.

How They Work

A marine chronometer shares the characteristics of other key-wound, spring-driven timekeepers, but has additional features that allow for greater precision at sea. Most importantly, it has particular devices that account for the changing conditions a ship will face during a voyage, such as motion, temperature and pressure.

The chronometer is used to keep accurate time for a fixed location, such as Greenwich Meantime (GMT). When a ship leaves port, the chronometer is set to GMT; during the journey, the navigator compares the local time with GMT to work out the time difference and consults a nautical almanac and sight-reduction tables to calculate the ship’s longitude.

4.

Legacy

The invention of the marine chronometer marked a turning point in the great seafaring age of the 18^th century. Thanks to John Harrison’s ingenuity – and perseverance – the Royal Navy gained an unassailable advantage over its rivals. British ships had the ability to navigate oceans with unprecedented accuracy, greatly aiding the expansion of the empire.

Famous explorers from Captain James Cook onwards relied on chronometers as they ventured into unchartered territory. However, by the 1960s, traditional marine chronometers were starting to be supplanted by electric engineering technology. Today, modern ships are equipped with electronic GPS systems, but many keep a chronometer on board, and the ability to use one is still a requirement of certain mariner qualifications.

5.

On the Market

Marine chronometers offer great scope for any collector.  By their nature, the quality in manufacture and finish had to be of the very highest order – men’s lives depended on their performance in extreme conditions – a chronometer would have to give as good a rate in the freezing Antarctic as it did on the burning equator.  Hinged gimbals and a weighted bowl ensured that it could cope with the choppiest of seas. 

Most chronometers that one finds today will run for about two days at a time – those that run for a full week tend to make higher prices and are often in fancier cases such as walnut or rosewood.  Fun fact - the highly specialised escapement inside the movement has a very particular  sound – rather than the ‘tick tock’ of a traditional clock, the chronometer beat is a reassuring ‘tick-tick’.