DE L'ISLE, Guillaume (1675-1726). Hemisphere Septentrional pour voir plus distinctement les Terres Arctiques. Paris: 1714. Engraved double-page map, period hand colouring in outline. Sheet size: 19 1/4 x 23 3/4 inches. Top margin trimmed close to plate mark, others wide; small abrasion in the Atlantic, mild soiling in margins.

Handsome early 18th century polar projection map of the northern hemisphere.

First edition of this polar projection of the Northern Hemisphere, drawn with scientific accuracy. De L'Isle is most highly regarded for his meticulous research and for leaving blank any area for which no knowledge was available; earlier cartographers were wont to insert guesswork coastlines and topographical features.

This map is the first to correctly place the west coast of North America by moving it substantially eastward from previous mappings. California is correctly shown as a peninsula (at a time when it was often still shown as an island). Much of the northwest of North America is left blank.

Polar projections distort increasingly as you approach the equatorial parts, but are accurate at the poles and arctic latitudes; the Mercator projection has just the opposite effect - giving northern latitudes disproportionate volume. This map corrects that impression.

Guillaume de l'Isle (1675-1726) was the son of a cartographer and a pupil of Jean Dominique Cassini, who, among other important contributions, aligned the study of astronomy to the study of geography. Under Cassini's direction, observations were made from locations all over the world that enabled longitudinal calculations to be made with much greater accuracy. De l'Isle carried on this exacting work with remarkable dedication and integrity, constantly revising and improving his maps. .