AMERICA, the general name by which the huge continent called the western hemisphere is now known. It is commonly agreed that the name is derived from that of the navigator, Amerigo Ves pucci (q.v.). America is divided geographically and ethnologically into three parts : North America (Canada and the United States of America) ; Central America and South America. These three divisions will be found treated separately under their own names.
Physical Geography.—The accidental use of a single name, America, for the pair of continents that together have a greater north-south extension than any other continuous land area of the earth, gives some support to the theory of its tetrahedral de formation; for America, broadening in the north toward its neighbours on the east and west, and tapering far to the south toward the Antarctic continent, roughly presents the triangular outline that is to be expected from tetrahedral warping. There is, however, not a unity but a duality, in its plan; North and South America resemble each other roughly in geological evolution as well as in outline, their chief correspondences being: (I) the area of ancient fundamental rocks in the north-east (Laurentian highlands, Guiana), without great deformation since early geo logical times; (2) the area of south-eastern highlands (Appa lachians, Brazil), with a crystalline belt near the ocean and more or less deformed Palaeozoic strata farther inland, both owing their present altitude to broad and modern geological uplifts; (3) the complex of younger mountains along the western coasts (Cordil leran highlands of both continents) of comparatively modern deformation and upheaval, associated with much volcanic activ ity; (4) confluent lower lands between the several highlands, with rivers flowing to the north (Mackenzie, Orinoco), east (St. Lawrence, Amazon), and south (Mississippi, La Plata). Differ ences are numerous, but they do not suffice to conceal the re semblance in general plan. Indeed, the chief differences between the two continents arise from their unlike position with respect to the equator. North America is bathed in frigid waters around its broad northern shores, its mountains in the north-west bear huge glaciers, the outlying north-eastern area of Greenland is shrouded with ice, and in geologically recent times a vast ice sheet spread over its north-eastern third ; while a warm and moist climate in its southern part gives it a torrid flora and fauna, and warm waters bring coral reefs to parts of its southern shores. South America has a torrid flora and fauna over its northern half and coral reefs on parts of its northern shores, while cold waters and glaciers characterize its narrowing southern end, where geo logically recent glaciation has taken place.
The similarity of outline between the western margin of the Old World and the eastern margin of the Americas, long ago noticed, has in recent years been taken to support a daring theory of continental fragmentation, according to which the Atlantic is thought to occupy the space left vacant when America floated away westward from its original moorings.
The relation of the Americas to the rest of the world as the home of plants and animals is greatly affected by the breadth of the adjacent oceans. Between the parallels of 6o° and 7o°N., the east-and-west widening of North America forms more than a third of the almost continuous land ring around a zone of sub Arctic climate; as a result there is a remarkable resemblance of plant and animal life in the high latitudes of North America and Eurasia. In strong contrast with this is the exceptional isolation of far southern South America, which but slightly interrupts a sub-Antarctic ocean ring; as a result, the land flora and fauna of South America to-day are strongly unlike those of the other south ending continents.
For further treatment of the physical geography of the American continents, see NORTH AMERICA and SOUTH AMERICA. (W. M. D.)