Rare Halley Chart Showing Magnetic Variation
"A New and Correct Chart Shewing the Variations of the Compass in the Western & Southern Oceans as Observed in the Year 1700", Halley, Edmund
Subject: Atlantic Ocean
Period: 1749 (published)
Publication: The English Pilot. The Fourth Book
Color: Hand Color
18.9 x 22.3 inches
48 x 56.6 cm
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 variation of Halley's original chart of the Atlantic Ocean shows magnetic variation of the compass, with the bold double-line crossing through Bermuda indication the line of no magnetic variation. The route of Halley's voyage is also shown. Place names are focused on the coasts, with the otherwise blank interiors of the continents supporting decorative cartouches. An image of a pair of diving ducks appears near the southern tip of South America along with a note explaining that an "animal of a middle species between a bird and a fish" can be seen in the seas in the area. A rare and interesting chart.
This appears to be the re-engraved edition by George Grierson, published in his pirated edition of The English Pilot, but with the text panels at right and left removed.
References: Shirley (BL Atlases) M.GRI-1a #1.
Issued folding with some soiling and two short fold separations that have been archivally repaired. Trimmed to neatlines at right and left.