A New and Correct Chart Shewing the Variations of the Compass in the Western & Southern Oceans in the year 1700 by his Ma[jes]ties's Command by Edm[und] Halley Tabula haec hydrographica variationum magneticarum index

TOGETHER WITH LETTERPRESS INSTRUCTIONS: HALLEY, Edmund (1656-1742) The Description and Uses of the New and Correct Sea Chart of the Western and Southern Ocean, Shewing the Variations of the Compass. [London]: R. and W. Mount, and T. Page, [1712] Engraved chart by I. Harris flanked by letterpress instructions affixed vertically to left and right sides of chart (Chart: 22 ½ x 19 in.; 57.2 x 48.3 cm. Overall with letterpress: 24 x 27 1/2 in.; 61 x 70 cm)., title cartouche over South America, secondary cartouche over Africa with dedication to William III. BINDING/CONDITION: Hinged to a mat. Creases where previously folded, several small paper repairs where letterpress was affixed to chart, costing one word in paragraph 2; some light browning. (65B1G) APPARENT FIRST EDITION OF HALLEY'S FAMED ISOGONIC CHART, WITH RARE EARLY ISSUE OF INSTRUCTIONAL TEXT. "AMONG THE RAREST OF CARTOGRAPHICAL TREASURES" (Tooley). An instrument of singular importance for navigation in the North and South Atlantic, of which few examples have survived. While Halley is perhaps best known for his computation of the orbit of Halley's comet, his theory of terrestrial magnetism is one of his most important scientific achievements. Between 1698 and 1700, Halley sailed across the Atlantic in the ship Paramour charting magnetic variation. By postulating the existence of four magnetic poles, Halley hoped to explain the magnetic variations recorded on the Earth's surface. He published two charts during his voyage on the Paramour, a meteorological chart in 1701, and the present magnetic chart in 1701/1702. The two were the first published charts with lines of equal magnetic variation I the oceans; these were referred to as "Halleyan lines" by his contemporaries, and are now known as Isogonic lines. "Thus the isoline, or line of equal value, was invented. For more than a century Halley's magnetic lines were a familiar feature of the world chart" (Shirley). Instrument, rather than chart, is the best designation of this early issue, for which the printed text provides instructions on use. Throughout the 18th century, the Mount & Page partnership and imprint went through numerous permutations. Robinson dates that of "R. and W. Mount, and T. Page" to 1712. An inspired work of science by one of the great astronomers of the age, which went on to be reprinted numerous times throughout the 18th century, including numerous editions of The English Pilot. PROVENANCE: Sotheby's New York, 12 December 2017, lot 37 REFERENCES: Louis A. Bauer, "Some Bibliographical Discoveries in Terrestrial Magnetism," in Nature 52 (1895), pp. 79-80; Edmund Halley and Thematic Geo-Cartography," in The Compleat Plattmaker; Robinson, Marine Cartography in Britain, pp. 117-121; Shirley, The Mapping of the World, p. xiv; Tooley, Maps and Mapmakers, p. 55; The World Encompassed, 199. …