Detailed map of the Western Hemisphere, most notable for its its depiction of Buache's conjectural Antarctic lands and interior sea and depict New Zealand as a part of Terres Antarctiques and fine early depiction of the Sea of the West.
In the interior of the imagined southern continent, Buache postualates a large Antarctic Sea, larger than that found in the northern polar regions. The map also provides one of the best early syntheses of the various theories for Northwest America, including a northwest passage, large early conception of the Aleutian islands and the Sea of the West.
Buache shows the route of the voyages of Abel Tasman (1642), Quiros, Magellan (1520), Le Maire (1616), Mendana (1568 and 1595). Davis's sighting of Icebergs southwest of the Straits of Magellan is oted, and the later voyages of Halley (1700), St. Louis (1708), Le Maire (1738) and Le Lion (1756) are also noted. In the North Pacific, the routes of Gaetan (1542), Tchirikow (1741) and the St. Antoine (1710) are noted.
The sea shown in the center of Antarctica was based upon a hypothesis Buache had developed over a number of years. His paper ' Geographical and physical observations, including a theory of the Antarctic regions and the frozen sea which they are supposed to contain' was published by The Gentleman's Magazine in 1763. In it, he hypothesised 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; the large sea (Mer Glacial, 'Glacial Sea') depicted on the 1739 map is an early version of this hypothesis. On the map, there is evidence of Buache's believe that the Southern Ocean includes two débouquements ('outlets'); he believed that Antarctica must possess rivers "as considerable as those of Siberia, which create the icebergs of the North". The map states that the sea is conjecturée.
Buache was an academic geographer who researched his material thoroughly, relying on the most up-to-date information from voyages of discovery. He was the first geographer to recognize the important concept of the watershed and it was this that led him to make a number of deductions, some correct, some not. A correct deduction was the existence of Alaska and the Bering Strait, years before they were officially discovered, while an incorrect deduction was the existence of a central Antarctic sea, which he conjectured to be the source of the icebergs observed by Bouvet in 1738-39.
There are those, including Hapgood, who see Buache's map as a tie in to the Piri Reiss map in the argument that these maps depict a subglacial land mass that is the Antaractic.
Philippe Buache (1700-1773) was one of the most famous French geographers of the eighteenth century. Buache was married to the daughter of the eminent Guillaume Delisle and worked with his father-in-law, carrying on the business after Guillaume died. Buache gained the title geographe du roi in 1729 and was elected to the Academie des Sciences in the same year. Buache was a pioneering theoretical geographer, especially as regards contour lines and watersheds. He is best known for his works such as Considérations géographiques et physiques sur les découvertes nouvelles dans la grande mer (Paris, 1754).