Papers of Nevil Maskelyne : Observations of John Crosley

Crosley, John

Papers of Nevil Maskelyne

The lunar and astronomical observations and rates of timekeepers made by the astronomer John Crosley, on the 1801 voyage to chart the coast of New Holland, led by Captain Matthew Flinders.The size of the volume owes to the limited amount of time Crosley spent on the voyage with the crew of the Investigator - leaving, as is written in its first page, at the Cape of Good Hope 'owing to illness'. This was, in fact, Crosley's second voyage, as he had previously served as an astronomer on board Captain William Broughton's 1793 voyage of discovery to the Pacific which had intended to assist Captain George Vancouver's surveying mission. Crosley had been brought in to replace the unfortunate William Gooch - the astronomer initially appointed for the voyage - who had been killed on the island of Oahu while on his way to meet with Vancouver, on 12 May 1792, after an encounter with the Hawaiian pahupu. In May 1797 while sailing from Macao as part of the voyage's adjustment of their plans, Crosley's ship, HMS Providence, had struck on a reef of coral, which led to him losing many of the observations he had taken, as well as losing or damaging all the timekeepers he had on board with him. It is presumably for this reason that Crosley takes care to mention in this volume that when on board the Investigator, he made sure to screw the Board of Longitude timekeepers into the ship's side in Captain Flinders' Cabin.We should be reminded that alongside the problem of selecting and then getting expensive instruments like timekeepers to function on voyages without breaking or stopping, the Board of Longitude and Admiralty had similar concerns over choosing appropriate personnel to place on these voyages. This becomes particularly noticeable for positions on voyages like the astronomer, in whom the Board of Longitude had to put in trust not simply to take possession of a whole range of expensive instruments, but also to be trusted to accurately use and test such instruments. The record of Crosley's use of the Board of Longitude's instruments is inscribed in this volume. Perhaps most noticeable are the amount of recordings - particularly relating to the three Arnold and three Earnshaw timekeepers - that have been derived on land rather than at sea. The reason for this is quite simply that for Crosley to know the rate at which the timekeepers on the ship were gaining or losing time - something that was entirely expected of timekeepers - with any certainty required the deployment of a land based observatory. As the voyage's appointed astronomer, it was Crosley's task to be in charge of this observatory and to make, as best he could, the astronomical observations necessary to calculate the rates of the timekeepers. Interestingly, Crosley doesn't mention anywhere how he had access to these timekeepers, which we had been told previously were screwed into the Captain's cabin - it would be surprising to think he would have had free access to the Cabin. What is clear is that for him to perform his duties as an astronomer would have required extensive interaction with Captain Flinders and other members of the ship's crew, which is rarely mentioned in the log books or journals made by Captains on voyages of discovery.Eóin Phillips History and Philosophy of Science University of Cambridge