ATLANTIC OCEAN, so called either from Mt. Atlas, or from the fabulous island of Atlantis, is that part of the ocean that. divides the old world from the new. Its extreme breadth is about 5000 m., and its narrowest part, between cape St. Roque, in Brazil, and the nearest point in Africa, about 1600 miles. If the A. be supposed to be bounded by the polar circles, and to include the Caribbean sea, Hudson bay, Mediterranean sea, and the other connected water-surfaces, it covers an area computed at 35 million sq. miles, The A. is naturally divided into three portions—the north, south, and inter tropical A. It stands in open connection with the D. and s. polar seas, and in the remarkable parallelism of its coasts, resembles rather a vast river than an ocean. Its northern half sends off numerous ramifications on both sides, some of them forming almost shut seas: on the w., Hudson's bay, the gulf of St. Lawrence, and the gulf of Mexico; on the e., the Baltic, North, Mediterranean, and Black seas. In the s., again, both coasts present a comparatively unbroken line; and there is a remarkable cor respondence between their projecting and retiring angles, the convex coast of Brazil lying opposite to the gulf of Guinea, and the projection of Senegambia answering to the retirement of the American coast in the Caribbean sea.
The whole of the new world, with the exception of the narrow strip lying w. of the Andes and Rocky mountains, belongs to the basin of this ocean. It drains compara tively little of the old world, as may be seen by tracing the water-shed on a map. Owing to the numerous seas and inlets connected with it, the extent of its shores is immense, over 50,000 m., several thousands more than that of the shores of the Pacific and Indian oceans. Except near the continents, the Atlantic is poor in islands compared with the Pacific. The chief islands in the open ocean are Iceland, Farb, Bermudas, Azores, Ascension, St. Helena, the Falkland islands, South Georgia, and Sandwich land.
The A. is the great highway of the civilized world, and everything that concerns its navigation is of great importance. Under the system of observations carried on for many years by the governments of Holland, Great Britain, the United States, and France, much has been done to amass information as to its currents, winds, depth, tem perature, etc., the chief results of which either have been or are in the course of being published. The operations connected with the telegraph-cable were also the means of
furnishing us with some valuable information regarding the Atlantic.
The chief A. currents are two The equatorial current, which, starting from about the island of St. Thomas, in the gulf of Guinea, with a rate of motion varying from 18 to 24 m. a day, proceeds westwards on both sides of the equator till near cape San Roque, where it divides, one branch running s. along the coast of Brazil, and the other along the coast of Guinea into the Caribbean sea. The velocity of this current is 24 m. a day at the point where it curves s., whence it gradually diminishes in strength as it proceeds southward to little more than 6 m. a day. Within the south A. there is a complete circulation of the waters, induced by the prevailing winds, and maintained at about 12 m. a day. Its forcd also varies with the months, being determined by the pre vailing force of the wind of each month. Its breadth varies from 200 to 400 m. ; and since it is fed by currents from n. and s. of it, its temperature is consequently considerably lower in the eastern than in the western part of its course. The other great current is the gulf stream. This, originally part of the equatorial current, after flowing past the Guinea coast, and through the Caribbean sea, issues from the gulf of Mexico through the strait of Florida, and after following the direction of the American coast to about 40°, turns seaward, touches the great Newfoundland bank, and gradually curving round, is lost as a distinct current about the Azores (see GULF STREAM). The of this stream is often upwards of 20° warmer than the surrounding ocean. The gulf stream has an immense influence on the Atlantic. Besides these great currents, the A. abounds in smaller ones, such as the northerly currents along the e. Greenland and Labrador coasts (this Arctic current extending as far s. as 36' n. lat., its rate being from 24 to 10 m. a day); the southerly current along the w. of Greenland; Rennel's cur rent, w. of the bay of Biscay; and the great current along the w. of Africa, from Morocco southwards, till it is merged in the Guinea current. The whole of these currents follow in every case the prevailing winds of the regions where they flow.