SCYTHIANS, a name very vaguely used by ancient writers. It was some times applied to all the nomadic tribes which wandered over the regions to the N. of the Black and the Caspian Seas, and to the E. of the latter. In the time of the Roman empire the name Scythia extended over Asia from the Volga to the frontiers of India.
SEA, a general name for the great body of salt water which covers the greater part of the earth's surface; the ocean. In a more limited sense the term is applied to a part of the ocean which from its position or configuration is looked upon as distinct and deserving of a special name, as the Mediterranean Sea, the Black Sea, etc. The term is also occasionally applied to inland lakes, as the Caspian Sea, the Sea of Galilee, etc.
Area.—The waters of the sea cover about 130,000,000 square miles, or about two-thirds of the surface of the earth. The areas of the main division of the ocean are estimated as follows: Depth.—The solid globe or lithosphere, viewed as to its superficial aspect, may be regarded as divided into two great planes; one of these corresponds to the dry land or upper surface of the con tinental masses, and occupies about two seventh of the earth's surface; the other, corresponding to the abysmal regions of the ocean, is depressed over miles be low the general level of the continental plane, and occupies about four-sevenths of the earth's surface. The transitional area, uniting these two planes, forms the sides or walls of the ocean basins, and occupies about one-seventh of the earth's surface. The depressed regions of the globe, represented by the ocean basins, are filled with sea water up to within about 375 fathoms (2,250 feet) of the general level of the continents, the aver age depth of the water in the ocean basins being on the other hand about 2,080 fathoms (12,480 feet). The aver age depths of the main divisions of the ocean are: The greatest depth hitherto recorded is 5,269 fathoms or 31,614 feet in the Pa cific near the island of Guam. In the Atlantic the greatest depth is 4,561 fathoms, off Porto Rico. Ross records a sounding in the Antarctic ocean where he found no bottom at 4,000 fathoms. By far the larger portion of the sea floor lies between the depths of 1,000 and 3,000 fathoms, equal to nearly 78 per cent., while about 171/2 per cent. is found in depths less than 1,000 fathoms, and about per cent. in depths greater than
3,000 fathoms. The bulk of water in the whole ocean is estimated at 315,000,000 cubic miles.
Tempera ture.—The temperature of the surface waters of the ocean varies from 28° F. in the polar regions to 85° or 86° in equatorial regions. In many places the surface layers are subject to great annual changes due to the seasons and the direction of the wind. The tem perature of the water at the bottom of the ocean over the abysmal areas ranges from 32.7° F. to 36.8° F. The great mass of the ocean consists of cold water e., of water below 40° or 45° F.; at a depth of little over half a mile the water in the tropics has generally a temperature below 40° F. In the open ocean the temperature usually decreases as the depth increases, the coldest water being found at the bottom. In inclosed or partially inclosed seas, cut off by bar riers from the great ocean basins, the temperature remains uniform from the height of the barrier down to the bottom; for instance, in the Mediterranean the temperature is about 56° from 200 fathoms down to 2,000 fathoms.
Circulation.—The circulation of oceanic waters is maintained by the action of the prevailing winds and by other causes. In the oceanic areas the prevailing winds are governed by the large anticyclonic areas situated toward the centers of the north and south Atlantic and north and south Pacific. The winds blow out from and around these anticyclonic areas. For instance, in the Southern Hemisphere the warm salt water of the tropical regions is driven to the S. along the E. coasts of South America, Africa, and Australia, till on reaching a latitude of between 50° and 55° S. it sinks on being cooled and spreads slowly over the floor of the ocean to the N. and S. A similar circulation takes place in the northern hemisphere, though much modified by the peculiar configuration of the land masses; for in stance, the cold salt water at 30° F. which occupies the deeper parts of the Arctic basin is largely made up of the dense Gulf Stream water, which sinks to the bottom on being cooled in the Nor wegian Sea. The water evaporated from the sea surface is borne to the land masses and condensed on the mountain slopes. The saltiest waters are found in the re gions of greatest evaporation; for in stance, in the Red Sea, Mediterranean, and in the trade-wind regions of the great ocean basins.