ATLANTIC OCEAN, the vast expanse of sea lying between the W. coasts of Europe and Africa and the E. coasts of North and South America, and extending from the Arctic to the Antarctic Oceans; greatest breadth, between the W. coast of northern Africa and the E. coast of Florida, 4,150 miles; least breadth, be tween Norway and Greenland, 930 miles; superficial extent, 25,000,000 square miles. The principal inlets and bays are Baffin and Hudson Bays, the Gulf of Mexico, the Caribbean Sea, the North Sea, or German Ocean, the Bay of Bis cay, and the Gulf of Guinea. The prin cipal islands N. of the equator are Ice land, the Faroe and British Islands, the Azores, Canaries, and Cape de Verde Islands, Newfoundland, Cape Breton, and the West India Islands; and S. of the equator, Ascension, St. Helena, and Tristan da Cunha.
Principal Currents.—The great cur rents of the Atlantic are the Equatorial current (divisible into the main, northern, and southern equatorial currents), the Gulf Stream, the north African and Guinea current, the southern connecting current, the southern Atlantic current, the Cape Horn current, Rennels cur rent, and the Arctic current. The current system is primarily set in motion by the trade winds which drive the water of the intertropical region from Africa toward the American coasts. Besides the surface currents, an under current of cold water flows from the poles to the equator, and an upper current of warm water from the equator toward the poles.
Depths.—The greatest depth yet dis covered is N. of Porto Rico, in the West Indies, namely 27,360 feet. Cross-sec tions of the North Atlantic between Eu rope and America show that its bed con sists of two great valleys lying in a north and south direction, and separated by a ridge, on which there is an average depth of 1,600 or 1,700 fathoms, while the valleys on either side sink to the depth of 3,000 or 4,000 fathoms. A ridge, called the Wyville-Thomson Ridge, with a depth of little more than 200 fathoms above it, runs from near the Butt of Lewis to Iceland, cutting off the colder water of the Arctic Ocean from the warmer water of the Atlantic. The South Atlantic, of which the greatest depth yet found is over 3,000 fathoms, resembles the North Atlantic in having an elevated plateau or ridge in the center, with a deep trough on either side. The saltiness and specific gravity of the Atlantic gradually diminish from the tropics to the poles, and also from within a short distance of the tropics to the equator. In the neighborhood of the British Isles the salt has been stated at one-thirty-eighth of the weight of the water. The North Atlantic is the great est highway of ocean traffic in the world.