088 Ship's Chronometer

This is a chronometer—a clock designed for accurate timekeeping on the move.

This specialist timekeeper was made for use on a ship. It contains a specific kind of mechanism, designed to keep the chronometer running at a constant rate in the varying temperatures and motions encountered at sea. The dial indicates hours, minutes and seconds. The whole machine is housed in a simple wooden box with mounts to keep it level—that’s important when you’re at sea as the motion of the ship could easily upset the delicate operation of the mechanism inside.

This chronometer was made in London, around the year 1800. The name of the maker, Thomas Earnshaw, and the place of manufacture are inscribed on its mechanism, which you can see on your screen now.

Having an accurate clock on board their ship allowed sailors to work out their longitude—their position east or west. By setting the time for Greenwich in London, they could use the noon sun at any location to work out how far they were from home. Today, the whole world still defines its local time and position in relation to London and the ‘Greenwich Meridian’. This is known as Greenwich Mean Time, or GMT.

This chronometer was used on a number of Royal Navy ships, but it was also among the timekeepers on board HMS Beagle, the ship that took Charles Darwin on his momentous voyage around the world. This voyage ultimately led to his theories of evolution. Darwin revolutionised our idea of time, suggesting that life on earth began millions of years earlier than had previously been thought.