<p style='text-align: justify;'>This group of documents consists mainly of records sent between 1774 and 1804 from around the globe to the Astronomer Royal Nevil Maskelyne of terrestrial observations for longitude. The papers show how Maskelyne’s Royal Greenwich observatory became a clearing-house for data from a worldwide network of observers, travelers and reporters.</p><p style='text-align: justify;'>The <a href='' onclick='store.loadPage(1);return false;'> first group (RGO 4/159: 1:1r)</a> records observations made at the Jesuit College in Peking between October 1772 and October 1774 of eclipses of the Sun and Moon, the positions of Venus and Jupiter, lunar distances from select fixed stars and planets, and the eclipses of Jupiter’s moons. The observers were all Jesuit officials of the Chinese imperial Astronomical Bureau, including the Portuguese José da Espinha, who later became director of the Bureau, together with an Italian glassworker Luigi Cipolla and the astronomer Joseph Bernard, using refracting telescopes of between 6 and 18 feet in length. These were the last years of the Jesuit mission in Peking and Jesuit astronomers’ work there. Annotated with judgments of observations’ quality, they provided longitude comparisons for European observers. Maskelyne also received <a href='' onclick='store.loadPage(15);return false;'> observations (RGO 4/159: 3:1r)</a> made near the East India Company’s trading base at Canton in southern China between September 1787 and January 1788 using a 46-inch refracting telescope to observe eclipses of Jupiter’s moons and, with the <i>Nautical Almanac</i>, derive a value for Canton’s longitude.</p><p style='text-align: justify;'>In 1774 Maskelyne also published an analysis of eclipses of Jupiter’s moons observed at the mouth of the St Lawrence River in Canada by the surveyor Thomas Wright. In 1796 Wright joined a joint commission with the United States to establish the boundary between New Brunswick and the district of Maine. In collaboration with the Harvard mathematics professor Samuel Webber, Wright determined the longitudes and latitudes of the rivers that formed the boundary. The <a href='' onclick='store.loadPage(19);return false;'> second version (RGO 4/159: 4:1r)</a> of the two astronomers’ report, completed in June 1799, with details of their fieldwork with telescopes and pendulums in September and October 1797, was sent to Maskelyne and is preserved here. In 1799 Wright provided a <a href='/view/MS-RGO-00004-00187/'> letter (RGO 4/187: 31:1r)</a> of introduction for Webber, now in Maskelyne’s correspondence. That correspondence also <a href='/view/MS-RGO-00004-00187/'> holds (RGO 4/187: 8:1r)</a> a 1774 letter from the astronomer and surveyor Gian Giuseppe Barzellini, reformer and surveyor based in the Austrian Habsburg city of Gorizia, while this collection contains Barzellini’s thorough <a href='' onclick='store.loadPage(37);return false;'> report (RGO 4/159: 7:1r)</a> on latitude observations and a diagram of his calculations.</p><p style='text-align: justify;'>In 1783 Maskelyne published instructions for observers of meteors, and held here is a report of such a meteor seen over Blackheath near Greenwich in July 1794. During the brief peace between Britain and France in 1802-3, Maskelyne got <a href='' onclick='store.loadPage(27);return false;'> details (RGO 4/159: 5:1r)</a> of the transit of Mercury seen in Paris by his scientific correspondent Jérôme Lalande and the eminent astronomers Pierre Méchain and Charles Messier. From the new East India Company observatory at Madras, the astronomer John Goldingham, employed there as assistant then from 1802 as director, sent <a href='' onclick='store.loadPage(49);return false;'> meteorological observations (RGO 4/159: 9:1r)</a> maintained since 1796, along with some notes on weather conditions in 1786-7. Fascinating evidence of the global reach of these information networks is provided by a <a href='' onclick='store.loadPage(29);return false;'> report (RGO 4/159: 6:1r)</a> from Fez in Morocco on a lunar eclipse of 26 January 1804 and a solar eclipse of 11 February 1804, sent by the remarkable Catalan traveler Domingo Badia y Leblich, who spent two years at the Moroccan court disguised as an Arab under the assumed name Ali Bey al-Abbasi, later working undercover in the Middle East. His message to European astronomers, a copy of which Maskelyne kept, appealed for systematic surveys of sunspot positions during eclipses, hoping thereby to determine longitude with more accuracy: <a href='' onclick='store.loadPage(34);return false;'> ‘one solitary terrestrial position fixed by these means would serve to correct a long series of geographical errors’ (RGO 4/159: 6:3v)</a>.</p><p style='text-align: justify;'>Simon Schaffer<br />History and Philosophy of Science<br />University of Cambridge<br /></p>
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