DIVISIONS OF THE OCEAN. The continents which are massed as great triangles within the hemisphere having Southern England for its pole separate the included portion of the hydrosphere into three broad arms—the Atlantic Ocean, be tween America and Europe-Africa ; the Pacific Ocean, between America anti Asia and the Indian Ocean, between Asia-Australia and Africa. Of these the Atlantic and Pacific com municate at their northern extremities through the Arctic Sea, which may be regarded as an extension of the Atlantic basin. The three oceans are further divided into northern and southern parts by the equator, but this division is conven tional and not based upon physical grounds. Southward, beyond the limits of the continents, they open out into avast expanse of shoeless water to which the name Southern Ocean may be conveniently given, the Antarctic Ocean being restricted to the area within the Antarctic Circle.
The borders of the ocean are often partially shut in by chains of islands, or they form deep re entrants into the continental lands, and such portions may have distinctive physical features. The mediterraneans. illustrated by the classic and the Gulf of .Mexico, arc in closed seas, communicating with the ocean only by narrow passages; their depths range from 1000 to 2000 fathoms and over limited areas even exceed the latter 4nire. Alarginal or fringing seas, partially inclosed by island groups, include waters of great depth like the Yellow Sea and the Japan Sea, and shallower bodies like the North Sea. Deep reiMtrants on emitinental har dens with broad openings toward the main ocean are illustrated by the Bay of Biscay and the Gulf of Guinea.