25 G PiiYSICAL GEOGRArUY OF THE SEA, AND ITS METEOROLOGY. 



which the sea performs in the economy of the universe by viitao 

 of its saltness, and which it could not perform were its waters 

 altogether fresh. And thus philosophers have a clew placed in 

 their hands which will probably guide them to one of the many 

 hidden treasures that are embraced in the true answer to the 

 question, " Why is the sea salt ?" 



485. Sea shells — their influence upon currents. — We find in sea 

 water other matter (§ 48) besides common salt. Lime is dis- 

 solved by the rains and the rivers, and emptied in vast quantities 

 into the ocean. Out of it, coral islands and coral reefs of great 

 extent — marl-beds, shell-banks, and infusorial deposits of enormous 

 magnitude, have been constructed by the inhabitants of the deep. 

 These creatures are endowed with the power of secreting, ap- 

 parently for their own purposes only, solid matter, which the 

 waters of the sea hold in solution. But this power was 

 given to them that they also might fulfil the part assigned 

 them in the economy of the universe. For to them, probably, 

 has been allotted the important ofiSce of assisting to give 

 circulation to the ocean, of helping to regulate the climates 

 of the earth, and of preserving the purity of the sea. The better 

 to comprehend how such creatures may influence currents and 

 climates, let us again suppose the ocean to be perfectly at rest — 

 that throughout, it is in a state of complete equilibrium — that, 

 with the exception of those tenants of the deep which have the 

 power of extracting from it the solid matter held in solution, 

 there is no agent in nature capable of disturbing that equilibrium 

 — ^and that all these fish, etc., have suspended their secretions, in 

 order that this state of a perfect aqueous equilibrium and repose 

 throughout the sea might be attained. In this state of things — 

 the waters of the sea being in perfect equilibrium — a single 

 mollusk or coralline, we will suppose, commences his secretions, 

 and abstracts from the sea water (§ 465) solid matter for his 

 cell. In that act this animal has destroyed the equilibrium of 

 the whole ocean, for the specific gravity of that portion of water 

 from which this solid matter has been abstracted is altered. 

 Having lost a portion of its solid contents, it has become spe- 

 cifically lighter than it was before ; it must, therefore, 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 



