The surface waters of the North Atlantic and the South Atlantic have each independent cir culatory systems. The Gulf Stream, in the North Atlantic, flows from the Gulf of Mexico along the eastern coast of the United States, but in latitude N. it loses its individuality and is merged with the general eastern surface drift. This latter spreads and divides, one branch of it flowing northward along the Nvegte•n coast of northern Europe, there, above latitude 70°, to join the colder currents flowing to the west: the other branch of it flowing southward along the western coast of southern Europe and that of northern Africa, there, below latitude 20° N., to join the warm westward current, and forming, between latitudes 10° and 45° N., a clockwise moving circulatory system. Off the western shores of the Atlantic the cold Arctic current flows southward from the north (called the Greenland Stream on the coact of Green land and the Labrador Stream farther south), part of it branching off toward the cast about latitude 50', and forming a return current, com pleting another counte•-clockwise system of cir culation between latitudes 45° and 00° N.
In the South Atlantic there appears to be hut a single great circulatory system, moving in a counter-clockwise direction. The sub-equato•ial water-current flows westward across the Atlantic in the region of the equator, but on reaching longitude 25' \V., it begins to separate, the north ern branch Moving toward the northwest along the Brazilian coast toward the Gulf of Mexico, and the southern branch moving toward the southwest and forming the Brazilian Stream along the eastern coast of Brazil; lint it turns eastward beyond latitude 40° S. and flows across the Atlantic with the general eastward drift of those southern latitudes. As the coast of Africa is approached, a part of the stream turns northward and flows along the southern part of the western coast of Guinea, where it is known as the Benguela Current, to join again the west ward current across the Atlantic near the equa tor. These various oceanic currents range in velocity from 20 to 75 miles per day.
The northern Atlantic lies in the path of the great procession of cyclones and anti-cyclones of middle latitudes, and also in the path of the West Indian hurricanes over its lower latitudes; the counterparts of these atmospheric disturb ances are found in the South Atlantic. The winds of the Atlantic are divided into two systems, those of the North and South Atlantic. In January and February, in the North Atlantic, north of latitude :35°, the winds are chiefly from the west; they are northwest on the North American coast, west toward the middle, and southwest on the European coast ; but between Iceland and Greenland there is an area of aver age cyclonic circulation (counter-clockwise). South of about latitude 35° N. the winds are generally from the northeast almost to the equator. In the South Atlantic, north of lati tude 20° S., in the western part, and north of
latitude 35° S., in the eastern part, the winds are from the southeast, becoming more distinctly from the south just at the equator. In latitude 30° S. the winds are from the south on the eastern side, and from the north on the western side: hut southward of latitude 40° S. they are in general from the west. Over an area whose centre is about latitude 30° S. and longitude 10° W. there is a system of winds flowing counter clockwise. In July and August the dividing lines between the wind systems of the North and South Atlantic are pushed farther northward by from 10° to 15°.
The mean annual rainfall over the Atlantic Ocean is in general from 00 to SO inches between latitude 4° S. and S° N.; between 10° and 30° N., 10 inches; from 30° to 40° N. it increases from 10 to 40 inches; in the middle ocean, from 42° to 58° N., SO inches. South of the equator the rainfall is from 20 to 40 inches in the western part, but from 10 to 20 inches in most of the eastern part; and increases in the middle ocean from 20 to 40 inches from latitude 10° to 35° S.
The vegetable and animal life of the Atlantic is treated under the subject OCEAN LIFE.
The distribution of alga: is dependent on the light and temperature of the water, and so rapid is the decrease of the former that below a depth of from 800 to 1000 feet few algae are found; those in the surface waters belong mainly to the Fucacefe, and those at greater depths are mainly Ceraminaoete. The chief feature of the •Vora which can receive mention here is the great Sar gasso region between latitudes 24° and 30° N. and longitudes 40° and 80° W., where the sea weed Sargassum baccife•um is found in such great abundance as to interfere in some places with the progress of sailing vessels.
The distribution of inammalia, fishes, and floating mollusks is determined largely by the temperature of the surface waters. Of the ceta •ea, some species of whales are distributed over various sections of the Atlantic Ocean, but those found in polar regions do not descend to lower latitudes, and vice versa.
The ocean bottom, near the coasts, is covered with a great variety of deposits of continental waste. The great portion, that between depths of 3000 and 12,000 feet, is, however, covered with Foraminifer:re (Globigerina, Orbulina, Pulvinu line, Spha-roidina). At these latter depths the calcareous bottom is replaced by gray clay, which forms a transition region between the fo•amini feran ooze and the red clay of the greater depths below 14,000 feet, which consequently covers a large area. The flora and the fauna of the regions of the Atlantic visited by the Challenger are given in minute detail in the Report of the Challenger Expedition, prepared under the direc tion of C. Wyville Thomson and John Murray (London, 18S0-95). See OCEAN; OCEANIC DE POSITS; DISTRIBUTION OF ANIMALS.