<p style='text-align: justify;'>This volume consists of draft letters and instructions written by Nevil Maskelyne to Ewart, Canelas, Dollond and Crosley, with a piece on Inman added. The <a href='' onclick='store.loadPage();return false;'> instructions (RGO 4/185:4)</a> to John Crosley in particular, form a vital role in the attempt by the Board of Longitude to try and manage the work of an astronomer on a voyage of discovery. Though addressed to Crosley, the instructions actually represent a standardised set of tasks which were given to all astronomers on voyages of discovery in this period by Nevil Maskelyne.</p><p style='text-align: justify;'>Like many astronomers sent by the Board of Longitude on voyages of discovery, Crosley had worked for several years as an assistant to Nevil Maskelyne at the Royal Observatory in Greenwich, where his tasks almost totally involved making the many observations and performing the rigorous calculations demanded for the Royal Observatory-produced Nautical Almanac. In 1793, he had been chosen by Nevil Maskelyne and the Board of Longitude to serve as an astronomer to supplement George Vancouver's 1791-95 surveying mission in the Pacific. Crosley had not been the first choice for this mission, but rather had to be hastily chosen to replace the astronomer William Gooch, who had been killed on the island of Oahu on 12 May 1792, after an encounter with the Hawaiian pahupu. As a replacement astronomer, Crosley had been issued with an almost identical set of instructions to those shown here. However the rigours of travel made it incredibly difficult for him to actually perform many of these - for instance, the ship the Providence struck coral off the coast of Macao, causing him to lose or damage many of his instruments and records of observations.</p><p style='text-align: justify;'>Crosley's experience on board HMS Investigator was significantly different. Indeed, he actually decided to leave the voyage at the Cape of Good Hope complaining of a bad case of gout.</p><p style='text-align: justify;'>Perhaps one of the oddest <a href='' onclick='store.loadPage();return false;'> directions (RGO 4/185:4)</a> for John Crosley was for him to teach officers how to perform the observations and calculations so that Longitude could be calculated from the moon's distance. This particular task can be understood partly as a move by Nevil Maskelyne and those astronomers associated with him from Greenwich to try and make the Nautical Almanac a practical solution to solving the problem of Longitude. However, in a similar way that from the instructions we might see just how hard it was to make sure timekeepers were keeping time accurately through a rigorous routine of winding and observing on sea and on land, to get the Nautical Almanac to a state so that it could be used as a means for finding Longitude, not only did the calculations made at Greenwich have to be trusted to have correct, but equally, it had to be thought that members of a ship's crew could deploy the technique of using a sextant and correctly carry out the mathematics required to derive Longitude. At the end of his <a href='/view/MS-RGO-00014-00058'> logbook (RGO 14/58)</a> from his 1772-1775 voyage on HMS Resolution, the astronomer William Wales complained that the knowledge of astronomy amongst members of a ship's crew was of such a poor state that they did not even understand the difference between a normal and an astronomical day. This was clearly a big problem when trying to get seamen to use the Nautical Almanac, and so alongside a push to get more officers learning mathematics on shore - typically unsuccessfully - it was hoped that astronomers on voyages could rectify some of these problems. Suffering from gout and leaving the voyage at the Cape of Good Hope, it is unlikely Crosley did much on the Investigator voyage to improve the situation.</p><p style='text-align: justify;'>Eóin Phillips<br />History and Philosophy of Science<br />University of Cambridge<br /></p>
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