Several mid-eighteenth-century maps, initially those of renowned theoretical geographer Philippe Buache, show a hypothetical depiction of what is now called Antarctica. The landmass is split into two with a large Mer Glaciale running through their middle. The smaller of the two is separated from Tierra del Fuego but extends north to land spotted by Bouvet de Lozier in 1739. Across the frozen sea is the larger of the two of Buache’s Antarctic lands. It extends east, running well south of Van Diemen’s Land, which had been skirted by Tasman in his voyage of 1642-3. Farther east in the Pacific the shore twists north to include New Zealand, which was also contacted by Tasman.
Bouvet’s sighting of Cap de la Circoncision is near one of the entrances to the polar sea. The other opening into the inland sea, to the southwest of South America, was placed where the buccaneers Sharpe and Davis had reported icebergs in 1687. Buache believed that the icebergs must have derived from a floating ice sheet, as in the Arctic. This hypothesis led him to conclude that the southern continent was not a single landmass but two islands separated by a frozen inland sea, from which icebergs detached themselves to float northwards.
The inland sea theory was based upon work Buache had developed over a number of years. His ideas were presented to the Académie des Sciences in 1744, published as Considérations géographiques sur les terres australes et antarctiques in 1761, and republished in English in The Gentleman's Magazine in 1763. In it, he hypothesized that the southern pole must contain a frozen sea, fed by mountain ranges and huge rivers in order to produce icebergs of the size reported by Bouvet, Halley, and others. The Antarctic inland sea was much discussed by geographers at the time and it was copied by several other mapmakers.