HALLEY, Edmond (1656-1743). Nova & accuratissima totius terrarum orbis Tabula Nautica variationum magneticarum index juxta observationes anno 1700 habitas constructa. Amsterdam: Hendrik Halma, ca 1702.
Hand-colored engraved map of the world, on 3 sheets joined, overall 540 x 1505 mm, showing the world on the Mercator projection, the Americas at center, with the Australian continent repeated at East and West, inset map of the North Polar regions. Contemporary outline and wash coloring. (A few small repaired tears.)
A very fine early example of the Halma issue of Halley's isogonic world chart. First published separately in 1702 by the London map publishers Mount and Page (and now unobtainable), two Dutch editions also appeared around the same time -- one by pierre Mortier, and this extremely rare edition by Hendrik Halma. One of Halley's important scientific contributions was his theory of terrestrial magnetism, in which he attempted to explain the variations in magnetic variations recorded on the earth's surface by postulating the existence of four magnetic poles. Between 1698 and 1700 Halley crossed the Atlantic as captain of the ship Paramore, during which voyage he charted magnetic variation in hopes of using the information to determine longitude at sea. Although this proved unsuccessful, he published two innovative charts in 1701 and 1702, the first of the Atlantic Ocean, the second the present world chart. These were the first published charts to indicate isogonic lines, or lines of equal magnetic variation in the oceans (called 'Halleyan lines' by contemporaries), a project that had been planned but apparently never carried out a century earlier by William Borough (cf. Waters, Art of Navigation, p. 161). "Thus the isoline, or lines of equal [magnetic] value, was invented. For more than a century Halley's magnetic lines were a familiar feature of the world chart" (Shirley, p. xiv). Cf. Koeman III, p. 87, no. 15, and IV, Ren 3, map 4; The World Encompassed. 200; N. J. W. Thrower, "Edmond Halley and thematic Geo-Cartography," in: The Compleat Plattmaker (Berkeley 1978), cf. pp. 215-218.