Papers of the Board of Longitude : Correspondence regarding methods of establishing longitude by lunar methods other than lunar distances

Papers of the Board of Longitude

<p>This volume contains the correspondence of those proposing alternative lunar methods for finding longitude. These correspondents do not adopt the method of lunar distances, an approach supported by the Board of Longitude following the publication of the first Nautical Almanac in 1767. Instead, they propose measuring the Moon's altitude alone. This method ultimately proved unpopular with the Board. As a consequence, the material in this volume sheds light on the Board's process of evaluation.</p> <p>The Astronomer Royal <a href='/search?keyword=Nevil%20Maskelyne'>Nevil Maskelyne</a> [<a target='_blank' class='externalLink' href=''><img title="Link to RMG" alt='NMM icon' class='nmm_icon' src='/images/general/nmm_small.png'/></a>] annotated a number of letters in this volume. In 1784, Maskelyne wrote [<a href='' onclick='store.loadPage(67);return false;'>35</a>] on the back of <a href='/search?keyword=Nicholas%20May'>Nicholas May</a>'s proposal that it 'does not appear to me to deserve the attention of the Board of Longitude'. On another letter [<a href='' onclick='store.loadPage(188);return false;'>100</a>] of 1789, a proposal from a <a href='/search?keyword=Mr%20Bright'>Mr Bright</a> of Liverpool, Maskelyne simply writes 'Not practicable', demonstrating a commitment to the Longitude Act's emphasis on the practicability of any potential solution. Despite Maskelyne's criticism of these alternative lunar methods, the Board continued to assess similar proposals based on the meridian altitude of the Moon well into the early nineteenth century. In 1815, for instance, <a href='/search?keyword=Mr%20R%20Paisley'>Mr R Paisley</a>, a mathematics teacher from <a href='/search?keyword=Edinburgh'>Edinburgh</a>, received a letter [<a href='' onclick='store.loadPage(424);return false;'>217</a>] informing him that the 'Commissioners do not approve' of his solution.</p> <p>Similar annotations on a number of other letters also indicate the date a particular proposal was read to the Board. For instance, <a href='/search?keyword=Charles%20Clarke'>Charles Clarke</a>'s letter [<a href='' onclick='store.loadPage(105);return false;'>55</a>] of December 18th 1786 was subsequently read on 3rd February 1787. These annotations allow readers to cross-reference material against the confirmed minutes [<a href='/view/MS-RGO-00014-00006/1'>RGO 14/6</a>] for a particular year. They also give a sense of the amount of time it took proposals to be evaluated as the Board developed.</p> <p>Whilst the majority of correspondents are based in Britain, there are also proposals originating from <a href='/search?keyword=France'>France</a>, <a href='/search?keyword=Italy'>Italy</a>, <a href='/search?keyword=Denmark'>Denmark</a> and the <a href='/search?keyword=Cape%20of%20Good%20Hope'>Cape of Good Hope</a>. This is in contrast to volume [<a href='/view/MS-RGO-00014-00033/1'>RGO 14/33</a>], in which correspondents suggesting refinements to the method of lunar distances are based exclusively in Britain. Alternative lunar methods appear to have looked more promising to those further from the influence of Greenwich and the Nautical Almanac.</p> <p>A number of foreign correspondents also used their proposals to introduce new instruments designed to aid the measurement of the Moon's altitude. <a href='/search?keyword=Heinrich%20Schultze'>Heinrich Schultze</a> of Copenhagen introduces [<a href='' onclick='store.loadPage(19);return false;'>10</a>] 'Schultze's Octant' alongside his own lunar method of 1779 whilst the Frenchman <a href='/search?keyword=Joseph%20Bonasera'>Joseph Bonasera</a> forwards a drawing [<a href='' onclick='store.loadPage(156);return false;'>83</a>] of his 'L'Horison De La Longitude', an orrery-like device designed to make simultaneous observations of multiple stellar objects.</p> <p>Further from Britain, conscious of the time it would take letters to arrive, foreign correspondents also worried more about claims to primacy. In 1811 a <a href='/search?keyword=Mr%20P%20Schonegevel'>Mr P Schonegevel</a>, writing from the Cape of Good Hope, went as far as to announce his method in the local newspaper, The Cape Town Gazette and African Advertiser. He then forwarded a copy [<a href='' onclick='store.loadPage(320);return false;'>169</a>] of this to the Board in order to establish himself as the original discoverer of his particular brand of lunar method. Schonegevel also had copies of his solution printed locally in Dutch in order to disseminate it amongst local mariners in the Cape, a tactic he shared with a number of British proposers such as <a href='/search?keyword=Joseph%20Barlow'>Joseph Barlow</a>.</p> <p>James Poskett<br />History and Philosophy of Science<br />University of Cambridge<br /> </p>

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