Papers of Nevil Maskelyne : Nautical astronomy

Papers of Nevil Maskelyne

A series of rough, handwritten calculations and problems for making observations at sea, and especially in finding longitude and latitude. All are by Nevil Maskelyne who was Astronomer Royal, a Commissioner of Longitude, and superintendent of the Nautical Almanac . Most are undated and may stem from any period from the 1770s-1810s when he was involved in this work, but dates on certain observations show a spread from at least 1783 to 1810.We see Maskelyne constantly trying to simplify and improve the calculations necessary to turn observations at sea into longitude and latitude co-ordinates; what in one <a href='' onclick='store.loadPage(61);return false;'> note (RGO 4/196:31r)</a> he describes as 'the pretty problem.' He uses a combination of lengthy calculations from specific, dated observations, and of problems which he sets himself and then works through, much like in any of the published manuals to teach navigational science. These appear in varying degrees of neatness, <a href='' onclick='store.loadPage(13);return false;'> one, for example, (RGO 4/196:7r)</a> being written on the back of an envelope. Some are clearly intended to be passed on for publication or to observers. He notes which problems have worked best, writing 'Best Problem' next to <a href='' onclick='store.loadPage(9);return false;'> one example (RGO 4/196:5r)</a> in a sheet of problems, and 'This is better chosen than the former' in another. <a href='' onclick='store.loadPage(21);return false;'> One sheet (RGO 4/196:11r)</a> also has the specific instruction that the notes are for 'Mr John Crosley to be communicated to Capt. Vancouver & Capt. Broughton from Dr Maskelyne.' This links these notes to other instructions given by the Board to Crosley, which <a href='/view/MS-RGO-00014-00001/309'> feature in Volume 1 (RGO 14/1:158r)</a> of the Board of Longitude archives.Maskelyne also evaluates other writer's methods, naming these specifically and, in some cases, referencing particular questions and page numbers in published works. He notes for himself which methods have proved useful and where the problems lie. In 1794, he <a href='' onclick='store.loadPage(39);return false;'> tries out (RGO 4/196:20r)</a> 'Mr Brinkley's' method and works out how to find the error in the result in 'Mr Greenwood's method' of calculation. In 1795, he tests <a href='' onclick='store.loadPage(37);return false;'> another (RGO 4/196:19r)</a> communicated by Mendoza de Rios as 'a friend's' but Maskelyne notes that he suspects it is Mendoza's own. Mendoza's lunar tables did win a reward from the Board of Longitude, but here Maskelyne notes that his own rule is more convenient. At another point he considers the results of Mr Cagnioli's 'analytical calculations' and notes to himself that these are the same as in Taylor's logarithms. We see the energetic and conscientious effort which Maskelyne put into ensuring the accuracy of the Nautical Almanac.It is not known if the pages are foliated in their original order.Katy Barrett History and Philosophy of Science University of Cambridge