 The Beagle was sent in 1831 on a survey mission which involved circumnavigating the globe, a journey described by the naturalist on board the ship, Charles Darwin, in his book The Voyage of the Beagle and which lasted until 1836. It was on this journey that Darwin began to form the ideas published much later as On the Origin of Species. The Beagle carried twenty-two chronometers, an unusually large number, but necessary to ensure accuracy of the survey. Three would have been commonplace on ships of the time, as this is the minimum number required to easily identify one that has gone faulty. The Admiralty started a general issue of chronometers to H. M. Ships from 1825, but between about 1800 and 1840 the availability of chronometers could not keep up with the demand. The Admiralty therefore only issued one chronometer to each ship unless the Captain personally owned one. In those cases the Admiralty would issue a second machine to make the total up to three, reasoning that a ship with two was no better off than with one since in the event of a discrepancy it was not possible to identify the faulty instrument.
