1797 Carte des Déclinaisons et Inclinaisons de l’Aiguille Aimantée
DESCRIPTION
An uncommon late 18th-century scientific chart plotting magnetic declination and inclination across the Atlantic Ocean, North Pacific, and the Americas, extending from the Arctic regions and Hudson Bay south through North America, Mexico, the Caribbean, and into South America. Rather than presenting a conventional political or geographic map, the cartography prioritizes numerical magnetic observations, with degrees of variation carefully recorded across open water and along coastal margins.
Landmasses are shown selectively and often incompletely, reinforcing the chart’s analytical purpose. The Pacific Northwest, including Nootka Sound, appears with partial coastal detail, while the eastern seaboard of North America, Hudson Bay, and James Bay are more fully outlined as reference points for magnetic readings. The interiors of continents are largely blank, and coastlines fade or terminate where they were not essential to plotting observations, making clear that geographic completeness was secondary to scientific accuracy.
Produced for the 1797 Paris publication of the Atlas du Voyage de La Pérouse, this chart synthesizes magnetic data gathered by French navigators beginning in 1775 and refined during the expedition commanded by Jean-François de Galaup, under the scientific direction of Jean-Charles de Borda. Its dense numerical notation, sparse geography, and emphasis on the oceans underscore its role as a practical navigational tool, intended to help mariners correct compass error during long transoceanic voyages.
CONDITION
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