shores and around some of the volcanic cones which rise from this floor there are very steep slopes. Life exists at all depths of the sea, though becoming less abundant at greater depths; while the surface waters from equator to poles swarm with all kinds of plants and animals, many of which give forth a phosphorescent light, causing what is known as the luminosity of the sea.
Though only about half as large as the Pacific Ocean, the Atlantic is much more important, as the most civilized nations of the world live on its shores and it is the great highway of trade for the world. Its coasts are better surveyed and better provided with lighthouses than those of any other ocean. It is divided by the equator into the North Atlantic and South Atlantic, with respective areas of 14,000,000 and 10,000,000 square miles. It is estimated that the yearly discharge of rivers into the Atlantic is 3,400 cubic miles of water, equal to about one half of the river discharge of the world.
There are warm and cold currents in the Atlantic, which have an effect on the neighboring lands. The most important is the Gulf Stream. It starts from the Gulf of Mexico and spreads out over the ocean to the south of Newfoundland; one part of it returns to the tropics off the coasts of Spain and Africa; the other passes northward between the British Isles and Iceland and on to the coasts of Norway, which are thus rendered habitable, though the opposite coasts of Greenland are icebound.
The chief inlets of the Atlantic are, on the west, Baffin Bay, Davis and Hudson Straits, the Gulf of St. Lawrence, Gulf of Mexico and Caribbean Sea; and on the east the North and Baltic Seas, Bay of Biscay, Strait of Gibraltar and Gulf of Guinea. The principal islands washed by the ocean are, on the west, Newfoundland, Bermuda, Bahama and West India Islands, Trinidad and the Falkland Islands; and on the east, Iceland, Faroe, Shetland, Orkney and the British Islands, the Azores, Madeira, Canary and Cape Verd Islands, together with St. Paul, Ascension and St. Helena. Some twenty cables now cross the Atlantic floor between the Old World and the New; while the Marconi wireless system, now successfully inagurated, adds to the facilities of international communication.
Atlan'tis, in ancient tradition the name of a vast island in the Atlantic Ocean. Plato relates, in his dialogue Timoeus, how an Egyptian priest told Solon of its existence, lying off the Pillars of Hercules in the ocean and larger than Libya and Asia Minor together. Plato also gives a description of the island and adds a fabulous history. His story is that 9,000 years before his own time Atlantis was a powerful and populous island, and conquered the western part of Europe and Africa. At one time its whole power was arrayed against the nations bordering on the Mediterranean, and every nation gave way before it except the Athenians, who were finally victorious. The gods at last came to the rescue of the earth and an earthquake caused the island to sink in £Ke ocean. Many efforts have been made to find the seat of this island, but it doubtless was only an imaginary land, like the Land of the Dead among the Celtic race.
At'las, in Greek fable, the son of a Titan and father of the Pleiades and Hyades. As leader of the Titans he tried to storm the heavens, and for this crime was condemned by Zeus to bear the vault of heaven on his head and hands, standing in the neighborhood of the Hesperides at the western end of the earth on the mountains in the northwest of Africa, still called by his name.
Atlas, the great mountain system of northwestern Africa, stretching from Cape Nun in Morocco to Cape Bon in Tunis, a distance of about 1,400 miles. It is a very irregular mass of mountains running in various directions. It reaches its greatest height (about 13,000 feet) 27 miles southeast of the city of Morocco, and in the peaks Bibawan and Tagherain. The heights approach the sea and form the promontories jutting out into the Atlantic. The slopes of the north, west and south are covered with vast forests of rjine, oak, cork, white poplar, etc. Copper, iron, lead and antimony are found abundantly, but have not yet been mined to any great extent.
Atoll (ȧ-tŏl '), the native name commonly applied in the Indian Ocean to a lagoon island, a low, usually circular reef, often composed of coral and the sand and soil washed up by the sea, and upon which a stunted vegetation grows, with an occasional palm tree a variety of shrubs. Many atolls are as much as a hundred miles in circumference, and enclose bodies of water varying from 12 to 50 fathoms; they furnish good temporary harbors, open here and there, by narrow inlets from the sea. In many cases they are inhabited by Malays. See Coral Island and Reef.
At'om. When a homogenous body is broken up into very small parts, even the smallest parts which we can produce by any instrument or see by any microscope, these parts appear to be all exactly alike in structure. But we may fairly ask whether, if it were possible to continue the process of division yet further, we should still find the body made up of parts exactly alike. The facts indicate that this question would have to be answered in the negative. For there are other methods, besides the use of mechanical instruments, for separating a
