Page:Physical Geography of the Sea and its Meteorology.djvu/283

Rh attains the exact degree of specific gravity due to sea water generally.

486. Solid matter secreted by them.—How much solid matter does the whole host of marine plants and animals abstract from sea water daily? Is it a thousand pounds, or a thousand millions of tons? No one can say. But, whatever be its weight, it is so much of the power of gravity applied to the dynamical forces of the ocean. And this power is derived from the salts of the sea, through the agency of sea-shells and other marine animals, that of themselves scarcely possess the power of locomotion. Yet they have power to put the whole sea in motion, from the equator to the poles, and from top to bottom. But we have yet to inquire how far may currents be due to the derangement of equilibrium arising from the change of specific gravity caused by the secretions of the myriads of marine animals that are continually at work in various parts of the ocean. These little creatures abstract from sea water solid matter enough to build continents of. And, also, we have to remember as to the extent to which equilibrium in the-sea is disturbed by the salts which evaporation leaves behind. Thus, when we consider the salts of the sea in one point of view, we see the winds and the marine animals operating upon the waters, and, in certain parts of the ocean, developing by their action upon the solid contents of the same those very principles of antagonistic forces which hold the earth in its orbit, and preserve the harmonies of the universe.

487. Dynamical force derived from.—From another point of view, we see the sea-breeze and the sea-shell, in performing their appointed offices, so acting as to give rise to a reciprocating motion in the waters; and thus they impart to the ocean dynamical forces also for its circulation. The sea-breeze plays upon the surface; it converts only fresh water into vapour, and leaves the solid matter behind. The surface water thus becomes specifically heavier, and sinks. On the other hand, the little marine architect below, as he works upon his coral edifice at the bottom, abstracts from the water there a portion of its solid contents; it therefore becomes specifically lighter, and up it goes, ascending to the top with increased velocity, to take the place of the descending column, which, by the action of the winds, has been sent down loaded with fresh food and materials for the busy little mason in the depths below. Seeing, then, that the inhabitants of the sea, with their powers of secretion, are competent to