A nautical chronometer made by Thomas Earnshaw (1749–1828), and once part of the equipment of HMS Beagle, the ship that carried Charles Darwin on his voyage around the world, is held in the British Museum.

By the time the Beagle set sail, it was being reported in The Nautical Magazine that the price of chronometers was dropping rapidly while the same quality was being maintained.

The Beagle carried twenty-two chronometers,[3] an unusually large number, but necessary to ensure accuracy of the survey.

[4] The Beagle however, would be gone for several years and was required to take chronometers ashore and in boat expeditions up rivers to determine the coordinates of specific reference points as instructed by the Admiralty.

[5] Each chronometer was mounted on gimbals to keep it level in all sea conditions, and the whole assembly fixed inside a hinged wooden box for protection.

[6][7] The chronometers were maintained by an instrument maker, one George James Stebbing, whose salary was paid for personally by the captain of the vessel, Robert FitzRoy.

This was impressive for a journey of tens of thousands of miles over five years; nevertheless Fitzroy considered the error to be inexplicably large.

William Edward Parry while exploring Baffin Bay in July 1819 during his first attempt to find the Northwest Passage mentions that Earnshaw's chronometer had been used in 1818 to determine the longitude of a spot to within 1' 30" of his own measurement.

[10] At this early time, all Royal Navy purchased chronometers were issued by the Greenwich Observatory who also checked their rates and sent them out for cleaning between voyages.

At this time Hecla was a famous ship: under the command of George Francis Lyon she had been part of Parry's second expedition to find the Northwest Passage.

The attempt ended in 1825 after the leading ship, HMS Fury was abandoned due to ice damage.

Parry unwillingly gave up Hecla when the admiralty sent her to survey the West African coast under the command of Bolder.

It sailed with Captain Fitzroy on Beagle's famous second voyage and was returned to Greenwich 7 November 1836.

After a period at Arnold and Dent for cleaning it was transported by HMS Lightning to Devonport or Portsmouth for issue to ships there.

The specialist contributors to the chronometer episode were Nigel Thrift, the vice-chancellor of the University of Warwick, and Steve Jones, geneticist and television presenter.