The full title of this map reads in English: A general map of the discoveries of Admiral de Fonte and other navigators, Spanish, English and Russian in quest of a passage to the South Sea by Mr. De l’Isle of the Royal Academy of Sciences, etc. Published at Paris in September 1752. This map is a spectacular example of imagination and fiction on the one hand and up-to-date cartography and information on the other. The fiction probably has its origin in a story appearing in a British magazine in 1708 and titled Memoirs for the Curious, an account of the imaginary voyage into the northern Pacific Ocean by a fictitious Spanish admiral named Bartholome de Fonte in 1640. Admiral de Fonte is supposed to have entered a strait leading east to an inland sea in which he encountered a westbound ship from Boston, which had sailed through the fabled Northwest Passage.
De l’Isle had returned to Paris after twenty-one years in Saint Petersburg and brought with him some hitherto secret imperial Russian maps acquired from the czarist Royal Academy of Sciences showing previously unreported Russian discoveries. He constructed a map accurately depicting eastern Siberia and the Kamchatka Peninsula but based the Pacific Northwest on the utterly fictitious de Fonte story, with a large Mer de L’Ouest (Sea of the West) to the north and east of Cape Mendocino.
Quivira is located on the southeast shore of this sea. The track that Admiral de Fonte is supposed to have taken in 1640 is shown proceeding along the coast north and around a major cape, where it winds through islands labeled Archipelago de St. Lazare and then east into a narrow strait that, although blocked by an impressive cataract, leads eventually to Hudson’s Bay and the Atlantic Ocean. Presumably, Admiral de Fonte encountered the westbound vessel in this narrow passage or in the wider opening to the east labeled Lac de Fonte. The detailed map in the upper left-hand corner appears to be an alternative version of the Archipelago de St. Lazare and the eastern passage to the Atlantic.
On the eastern portion of the map, however, M. de l’Isle, with his direct access in Saint Petersburg to current and until then, secret, maps of Russian discoveries, and personal experience on a voyage of exploration in the North Pacific, produced an up-to-date and generally accurate rendition of the Kamchatka Peninsula and eastern Siberia. The map also traces the voyages of Bering in 1727–1728, 1732–1734, and 1741 and the voyage of Captain Chirikov (with de l’Isle aboard) in 1740, none of which were previously known to European mapmakers.