196 THE PHYSICAL GEOGRAPHY OF THE SEA. 



in solution, there is no agent in nature capable of disturbing that 

 equilibrium — and that all these fish, etc., have suspended their se- 

 cretions, in order that this state of a perfect aqueous equilibrium 

 and repose throughout the sea might be attained. 



547. In this state of things — the waters of the sea being in 

 perfect equilibrium — a single moUusk or coralline, we will sup- 

 pose, commences his secretions, and abstracts from the sea water 

 (§ 498) solid matter for his cell. In that act, this animal has de- 

 stroyed the equilibrium of the whole ocean, for the specific gravity 

 of that portion of water from which this solid matter has been ab- 

 stracted, is altered. Having lost a portion of its solid contents, it 

 has become specifically lighter than it was before ; it must, there- 

 fore, give place to the pressure which the heavier water exerts to 

 push it aside and to occupy its place, and it must consequently 

 travel about and mingle with the waters of the other parts of the 

 ocean until its proportion of solid matter is returned to it, and 

 until it attains the exact degree of specific gravity due sea water 

 generally. 



548. 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. 



549. Those powerful and strange equatorial currents (§ 458), 

 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 



