OCEAN, the sea, using that term in its widest sense. Properly speaking, there is but one ocean or sea, all the salt water on the globe, with a few trifling excep tions like the Caspian, the Sea of Aral, And the Dead Sea, being more or less in complete communication with each other. Different portions of the ocean have re ceived distinctive names. The Arctic, the Atlantic, the Indian, the Pacific, and the Antarctic oceans, five in all; or if the Atlantic and Pacific be separated into a N. and a S. portion by the equator, then there are seven in all. The unequal heating of portions of the vast expanse of water on the globe, the rotation of the earth, and other causes tend to keep the water in constant circulation and pre serve it from being stagnant and im pure. The attractions of the moon and sun cause tides. The area of the ocean is about 155,000,000 square miles, or nearly three-fourths of the whole surface of the earth. This space is distributed
(in square miles) among the principal seas as follows: Arctic, 5,000,000; Antarctic, 10,000,000; Indian, 20,000,000; Atlantic, 40,000,000; Pacific, 80,000,000. This great volume of water largely mod ifies the temperature of the adjacent lands, tempering the heat of summer and the cold of winter. As far as observa tion has yet extended, the average depth of the ocean is somewhat above two miles. At 62° F., the relative density of salt and fresh water is as 1.0275 to 1. The ocean has been salt through all known geological periods. The origin of this saltness is a difficult geological prob lem. While on land the temperature rises as mines or borings become deeper, the opposite occurs with the ocean. As a rule, the surface water is the warmest. The level of the ocean remains perma nent from age to age. It is the land that is upheaved or subsides.