198 THE PHYSICAL GEOGRAPHY OF THE SEA. 



specific gravity of sea water, to destroy its equilibrium, to Ibeget 

 currents in tlie ocean, and to control its circulation, should be dis- 

 tributed according to order. 



554. Upon tliis supposition — the like of wliicli nature warrants 

 throughout her whole domain — we may conceive how the marine 

 animals of which we have been speaking may impress other fea- 

 tures upon the physical relations of the sea by assisting also to 

 regulate climates, and to adjust the temperature of certain lati- 

 tudes. For instance, let us suppose the waters in a certain part 

 of the torrid zone to be 90°, but, by reason of the fresh water 

 which has been taken from them in a state of vapor, and conse- 

 quently by reason of the proportionate increase of salts, these wa- 

 ters are heavier than waters that may be cooler, but not so salt 

 (§ 35). This being the case, the tendency would be for this warm, 

 but salt and heavy water, to flow off as an under current toward 

 the Polar or some other regions of lighter water. 



555. Now if the sea were not salt, there would be no coral isl- 

 ands to beautify its landscape and give variety to its features ; 

 sea-shells and marine insects could not operate upon the specific 

 gravity of its waters, nor give diversity to its climates ; neither 

 could evaporation give dynamical force to its circulation, and its 

 waters, ceasing to contract as their temperature falls below 39°, 

 would give but little impulse to its currents, and thus its circula- 

 tion would be torpid, and its bosom lack animation, 



556. This under current may be freighted with heat to temper 

 some hyperborean region or to soften some extra-tropical climate, 

 for we know that such is among the efiects of marine currents. 

 At starting, it might have been, if you please, so loaded with solid 

 matter, that, though its temperature were 90°, yet, by reason of 

 the quantity of such matter held in solution, its specific gravity 

 might have been greater even than that of extra-tropical sea water 

 generally at 28°. 



557. Notwithstanding this, it may be brought into contact, by 

 the way, with those kinds and quantities of marine organisms that 

 shall abstract solid matter enough to reduce its specific gravity, 

 and, instead of leaving it greater than common sea water at 28°, 

 make it less than common sea water at 39° ; consequently, in 



