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- 

 (luire 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 dynamical 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 



