DEFINITIONS GENERAL GEOGRAPHY OF THE OCEANS The vast collection of water which surrounds the land in every direction is commonly called the " Sea," and is really continuous and indivisible. The intervention of the great land-masses, however, is such that the sea can be conveniently divided into five more or less definite areas called oceans. It may be here remarked that the terms "ocean," "sea," are often used synonymously and applied indiscriminately to the great "world of waters" as a whole. But, geographically, the term ocean is limited to the largest divisions of water, and sea to smaller areas, entirely separated from, or broadly uniting with, the larger expanses called oceans. A gradual bend in the coast-line forms a bay,' but if the sea penetrates into the land for any considerable distance, a gulf' is formed. Smaller indentations form creeks,' harbours,' firths, fiords, and other variously-named inlets. A shallow body of salt water close to the sea, separated entirely or nearly so from it by a low sandy ridge, is called a lagoons or half.' Any considerable collection of salt water, surrounded or nearly so by land, are termed inland seas. The channels of communication between the larger bodies of water are also distinguished as straits,' if narrow and of no great length, or channels' if of greater length and width. The narrow arms of water between islands and the mainland are called sounds.' It will be readily perceived that while most of the above terms are exact and of general application, several are synony mous, and others are local, being restricted to certain countries.
Thus the terms firth or frith, lough, loch, fiord, &c., are synonymous in many cases, but the terms "firth," "loch," are restricted to Scotland; "lough" to Ireland; "fiord" to Norway. There is this further distinction, that " loch," in Scotland, is applied to narrow inlets of the sea as well as to actual lakes. The same may be said of " lough," in Ireland. The term "firth," or "frith," on the contrary, is restricted to arms of the sea, generally those receiving large rivers, and thus is equi valent to the term "estuary" in England and elsewhere. "Fiord," or "fjord," is indiscriminately applied to narrow inlets, and is peculiar to Norway and Denmark. The term "hall," again, is only used on the Prussian Baltic coast, " lagoon " being the equivalent term in the south of Europe and America The various movements of the ocean are distinguished as (1) currents,' or an onward motion of the water in certain localities, aptly described as "rivers in the ocean;" (2) waves,' billows,' and other surface-disturbances due to the action of winds and storms; (3) tides,' or the regular rising and falling of the water produced by lunar and solar attraction. A tidal wave rushing up a narrow strait or estuary frequently forms a bore or axgre.
The irregularity of the bottom of the sea, apparently elevated and depressed like the land, gives rise to banks, shoal 8, roads or roadsteads, harbours, pits, deeps, troughs, basin a. submarine ridges, &c.