166 
THE PHYSICAL GEOGRAPHY OF THE SEA. 
until it attains the exact degree of specific gravity due sea water 
generally. 
331. How much solid matter does the whole host of marine 
plants and animals abstract from sea water daily ? Is it a thou- 
sand 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. 
332. Those powerful and strange equatorial currents 270), 
which navigators tell us they encounter in the Pacific Ocean, to 
what are they due ? Coming from sources unknown, they are 
lost in the midst of the ocean. They are due, no doubt, to. some 
extent, to the effects of precipitation and evaporation, and the 
change of heat produced thereby. But we have yet to inquire, 
How far may they be due to the derangement of equilibrium aris- 
ing from the change of specific gravity caused by the secretions 
of the myriads of marine animals that are continually at work in 
those parts of the ocean? These abstract from sea water solid 
matter enough to build continents of. And, also, we have to in- 
quire 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, deriving from the 
solid contents of the same those very principles of antagonistic 
forces which hold the earth in its orbit, and preserve the harmo- 
nies of the universe. 
In another point of virw, we see how the sea-breeze and the 
sea-shell, in performing their appointed offices, act so as to give 
rise to a reciprocating motion in the waters ; and thus they impart 
to the ocean dy^amical forces also for its circulation. 
333. The sea-breeze plays upon the surface ; it converts only 
fresh water into vapor, 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 
