§ 472, 473. THE SALTS OF THE SEA. 2-^ 



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cany in. We now begin to perceive what a powerful impulse is 

 derived from the salts of the sea in giving effective and active 

 circulation to its waters. Hence we infer (§ 461) that the cur- 

 rents of the sea, by reason of its saltness, attain their maximum 

 of volume and velocit}^ Hence, too, we infer that the transporta- 

 tion of warm water from the equator toward the frozen regions of 

 the poles, and of cold water from the frigid toward the torrid zone, 

 is facilitated ; and consequently here, in the dynamical power which 

 the sea derives from its salts, have we not an agent by which cli- 

 mates are mitigated — by which they are softened and rendered 

 much more salubrious than it would be possible for them to be were 

 the waters of the ocean deprived of their property of saltness ? 



472. This property of saltness imparts to the waters of the 

 A property peculiar occau auothcr peculiarity, by which the sea is still 

 to seas of salt water, i^g^ter adapted for the regulation of climates, and it 

 is this : by evaporating fresh water from the salt in the tropics, 

 the surface water becomes heavier than the average of sea water 

 (§ 427). This heavy water is also warm water; it sinks, and be- 

 ing a good retainer, but a bad conductor of heat, this warm water 

 is employed in transporting through under currents heat for the 

 mitigation of climates in far-distant regions. Now this also is a 

 property which a sea of fresh water could not have (§ 430). Let 

 the winds take np their vapor from a sheet of fresh water, and 

 that at the bottom is not disturbed, for there is no change in the 

 specific gravity of that at the surface by which that at the bottom 

 may be brought to the top ; but let evaporation go on, though 

 never so gently, from salt water, and the specific gravity of that 

 at the top will soon be so changed as (§ 404) to bring that from 

 the very lowest depths of the sea to the top. 



473. If all the salts of the sea were precipitated and spread 

 Quantity of salt in ^^^ cqually ovcr the northern half of this continent, 

 "'® '^*' it would, it has been computed, cover the ground 

 one mile deep. What force could move such a mass of matter on 

 the dry land? Yet the machinery of the ocean, of which it forms 

 a part, is so wisely, marvelously, and wonderfully compensated, 

 that the most gentle breeze that plays on its bosom, the tiniest in- 

 sect that secretes solid matter for its sea-shell, is capable of put- 

 ting it instantly in motion. Still, when solidified and placed in a 

 heap, all the mechanical contrivances of man, aided by the tre- 



