Edmund Halley (1656-1742) was an English astronomer, meteorologist, and physicist best known for calculating the orbit of the eponymous Halley's Comet. In 1686 Halley became the first to depict trade winds and monsoons on a map, which appeared on his untitled diagrammatic world map. Halley was granted temporary Captainship in the Royal Navy for his scientific voyage through the Atlantic on the ship Paramore, during which he investigated the laws governing the variation of the compass. He published his findings in General Chart of the Variation of the Compass (1701), a chart of the Atlantic ocean which was the first to use isogonic, or Halleyan, lines to show the pattern of magnetic variation. The following year Halley extended his chart to the western Pacific, using data from journals of voyages in the Indian Seas.

This reduced version of Halley's original chart shows magnetic variation of the compass, with bold double-lines crossing through Bermuda and southeast Asia indicating no magnetic variation. Trade winds are depicted primarily between the Tropic of Cancer and Capricorn. California appears as an island with an indented northern coast with several small islands between it and the mainland. The Great Lakes do not appear. New Guinea appears to still be connected to Australia and New Zealand is only partially delineated. An inset of the polar region is included at bottom along with a note stating that the large two-sheet map of the world is sold by R. Mount and T. Page on Great Tower Hill, London. Engraved by John Harris.

References: cf. Shirley (BL Atlases) M.Hall-1a #1 & #2.

Condition: B

Issued folding and trimmed to the neatline at bottom, with a few small portions of the neatline missing. There is a binding trim at lower right and associated 0.5" binding tear. Light soiling with a few chips and fold separations at top and bottom.