THE ANTARCTIC OCEAN GENERALITIES The Antarctic Ocean is the name given to the whole body of water comprised within the Antarctic Circle, but which is of limited extent, if it be true that the various portions of land sighted on or near the circle are the coasts of an immense circumpolar continent. The Antarctic Circle is for the most part merely a theoretical or imaginary boundary, there being no continuous natural limit to the South Polar basin, which opens broadly into the Pacific, Atlantic, and Indian Oceans. The portions of these oceans extending south of Cape Horn, Cape of Good Hope, and Tasmania, to the Antarctic Circle, belong therefore, naturally, to a continuous depression extending right round the globe, and gradually shoaling towards the South Pole. The whole of this expanse, as well as the water area actually within the Antarctic Circle, forms, in fact, but one ocean—the great " Southern Ocean "—which is, physically, the most important of all the divisions of the great "world of waters." It is in this vast basin that those grand movements of tides and currents originate—here they receive their primary impulse, and hence they are propagated into the other great oceans.
As the Atlantic, Pacific, and Indian Oceans commu nicate freely towards the south, there was no necessity—as in the case of the Arctic Ocean, where the passage both east and west is blocked by land and ice—for any investigation of the Antarctic Ocean from a purely commercial point of view, and it thus offered but few inducements which stimulated repeated researches in the Arctic Seas ; and moreover, the violent tempests which sweep over this inhospitable waste of waters, together with the vast number of icebergs which constantly encumber it, render its navigation most difficult and dangerous. A few daring navigators have indeed gal lantly crossed the Antarctic Circle, but with the exception of Sir James Ross and Weddell, none of them reached the 72nd parallel : all being stopped by icefields or icebanks, skirting inaccessible coasts, lying generally on or near the Antarctic Circle. The principal known points are Graham Land, Trinity Land, with the adjoining islands, Alexander, Adelaide, South Shetlands, South Orkneys, &c., south of Tierra del Fuego ; Enderby and Kemp Land, south of the Crozet Islands : the irregular coasts of Sabrina Land, Clarie Land, and Adelie Land, south of Australia ; and the great bend off the Balleny Islands, penetrated by Sir James Ross as far as lat. 78° 15' S., where he found "an unbroken ver tical cliff of ice, of about 1,000 feet in thickness, and floating in 280 fathoms. of water, extending eastward for 450 miles." The principal landmarks on the dreary and most inhospitable coast of Victoria Land are a range of mountains running south, culminating in Mts. Sabine, Crozier, Erebus, an active volcano 12,367 feet high, and Terror, an extinct volcano, 10,889 feet above the sea level.
The portions of land discovered within the Antarctic Circle is almost everywhere inaccessible, and, where sur rounded by open water, landing is rendered impossible by enormous icebanks, of from 5 to 20 miles wide, which skirt the coasts. The mountains of Adelie Land are probably of an average height of 1,000 feet, with almost vertical slopes ; the intervening valleys being filled with ice and snow, pressed by continual accumulations into vast glaciers. The con stantly increasing pressure forces the glaciers forward, so that their lower ends project far out in the water. By the action of the waves, tides, and storms, vast pieces are continually being broken off, and thus are formed the icebergs of the Southern Ocean, immense numbers of which are found even in summer as far north as or 50°—that is, 10° nearer the equator than those of the Arctic Ocean. The Antarctic ice-, bergs are not, like those of the North Polar Sea, irregular and fantastic in shape, but are mostly flat-topped, rising per pendicularly out of the water. The vast belt of water between 50° and 70° S. lat. being constantly covered with ice, either in immense " fields " or detached " floes " or "bergs," is con sequently kept at a low temperature ; hence the coldness of the vast north-easterly drift known as the Antarctic drift current.
In the wide inlet discovered by Ross, the depth no where exceeded 500 fathoms, and it is probable that the aver age depth of the deepest parts within the Antarctic Circle is under 1,500 fathoms. The maximum depth found within the Antarctic Circle by the Challenger expedition, south of Termination Island, was 1,975 fathoms, or 11,850 feet.
The whole of the Antarctic regions are within the snow-line, and no vegetation is known to exist south of Cockburn Island (64° 12' S. lat., 49' W. long.), and even there it disappears entirely at an elevation of 1,000 feet. In reference to the animal life of the South Polar regions, Sir John Richardson says that "no terrestrial quadruped inhabits the lands within the Antarctic Circle ; the marine cetaceans and seals being the only mammals that enter its area, or approach it within many degrees of latitude. Organised specially to inhabit the chilly Antarctic waste of waters, the almost scaly penguins resemble the walrus and seals, in being able to travel long and far beneath the surface of the ocean in seeking their food in its depths, and scarcely quitting it except for the purpose of incubation. Indeed, one species— the solitary penguin—carries its eggs with it in a fold of skin when it roams far in search of food. The existence of such a creature, and of the dodo, moa, &c., furnishes an argument of certain species having been created solely for limited districts."