therefore only issued one chronometer to each ship unless the Captain personally owned one. In those cases the Admiralty would issue another to take the total to three, reasoning that a ship with two was no better off than with one since a faulty instrument could not be identified. 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. It could not be guaranteed that any one chronometer would continue to function accurately, or even survive the journey at all. 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. For additional protection, they were stored in sawdust in a special cabin in the Captain's quarters. Only crew who needed to take measurements, or who maintained them, were allowed access, measures which indicate the importance attached to these instruments. The Beagle voyage succeeded, for the first time, in establishing a linked chain of reference points around the globe of known longitude which could be used by subsequent voyages to calibrate their own chronometers.Nicholas and Nicholas, pp.5-6. Maintenance and accuracy 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. FitzRoy considered the post to be essential to the mission but the Admiralty had refused to pay for it. FitzRoy bore the cost himself, as he did for much of the ship's equipment, but the Admiralty did concede that Stebbing could be fed from the ship's rations. This concession was not extended to Darwin, who paid £500 for his own keep. By using his chronometers to measure the time of local noon when he returned to his home port Fitzroy was able to measure the overall accuracy of the entire voyage. As he sailed west, local noon occurred progressively later, until finally, when he had circumnavigated the globe, the shift in local noon time, as measured by his chronometers should be exactly twenty-four hours. In fact, Fitzroy's measurements exceeded this by 33 seconds, which is equivalent to just . This was impressive for a journey of tens of thousands of miles over five years; nevertheless Fitzroy considered the error to be inexplicably large. History