INTRODUCTION GENERAL GEOGRAPHY OF THE OCEANS Although it may be taken for granted that the various terms which we shall have occasion to use in the following pages are already sufficiently familiar to the student, yet, bearing in mind that nothing is so important in scientific description as exactness and accuracy of meaning and applica tion of the terms used, it will be necessary to furnish the student with more precise definitions than are generally given. Many of the terms are simple, it is true, but several of them have a peculiar significance of meaning, which is too fre quently overlooked, and thus wrong impressions are formed by the loose application of apparently simple terms.
Viewing the earth as a whole, we find its outer crust characterized by extremely irregular elevations and depres sions—the more elevated portions constituting the land masses, while the considerably depressed portions form the receptacle for a vast body of water, configured by the inter vening masses of land into certain more or less definite areas, called oceans. Generally speaking, the waters of the ocean cover every part of the earth's outer crust up to a certain fixed limit called the sea-level.
But, besides the extreme irregularity in elevation, there is also, as a glance at a map of the World will show, a corres ponding irregularity in horizontal configuration, the latter being, in fact, a result of the former. Even a cursory examination of the contours of the great land masses will con vince the student that the " line of contact " between the sea and the land is not mathematically precise. In some parts the coast-line is regular and unbroken, but generally quite the reverse, the sea penetrating into or actually inter vening between the masses of land in an endless variety of ways. And although with a few exceptions, the great waters of the globe form one continuous and connected expanse, the irregularity of the line of contact with the land necessitates the use of various terms, showing the mutual relations, as to position and extent, of the sea and the land.