The sea is a general name given to all the greater collections of water throughout the world, although, in a restricted sense, it is applied to those tracts of water of a secondary size, as the Black Sea, the Baltic, and the Mediterranean, the term "ocean" being applied to the larger tracts of water, as the Atlantic Ocean, the Pacific Ocean, &c. All the great oceans and seas unite, and, in reality, form one great world of waters, spread out and covering all the lower parts of the earth, the term "lake" being applied to collections of water surrounded by land, although the Caspian Sea retains the name of sea, and some of the great lakes of America may well deserve such a name. The waters of the sea fill up all the lower parts of the earth, so that, almost without exception, the land is higher than the water, and as the land in some places rises but a few feet, and in others as many thousands, so, beneath the sea, the land sinks in many places but a few feet, and in others perhaps as many thousands as it is known to rise above it. The sea always maintains the same general level, although in past ages the land has risen and fallen, sometimes in one place and sometimes in another; indeed, the same process is taking place every day, but in so slow a manner that centuries are required to make any great alteration; while some tracts of land are being encroached on by the action of the waves, others are being added to and elevated by accumulations of mud and sand, or raised by the action of earthquakes and volcanoes, which throw up under the sea, as well as on the land, vast quantities of melted earth or lava, forming strata known to geologists as basalt, tufa, &c., or eject showers of ashes and dust in such prodigious quantities as to cover many hundred square miles of the earth's surface. It was by one of these showers of ashes from Vesuvius that the cities of Herculaneum and Pompeii were buried. So that, as a whole, although the sea is continually altering slowly its position, yet it pretty equally maintains the same elevation. At first thought it may be supposed that the rivers constantly flowing into the sea would alter its level, for some are so large that millions of tons of water are brought by them into the sea every hour, and there are thousands of rivers and rills which, night and day, pour in their tribute of waters; but God has wisely and kindly arranged these things (like all others) so that they shall afford us innumerable comforts, and yet not raise up the sea so that it shall cover the land, for it requires but a moment's consideration to be convinced that all this water which flows into the sea must first have been abstracted from it, and it is in this way--when the winds blow over the sea, they absorb or take up a certain quantity of the vapour which continually rises from it; for air absorbs a certain quantity, and a certain quantity only, of the vapour of water; but this quantity is determined by certain circumstances,