THE SALTS OF THE SEA. 255 



the water of the under current, inasmuch as it comes from the 

 south, and therefore from warmer latitudes, is not so cold ; and 

 if it be not so cold, its temperature, before it comes out again, 

 must be reduced to 28°, or whatever be the average temperature 

 of the outer but surface current. Dr. Kane found the temperature 

 of the open sea in the Arctic Ocean (§ 429) as high as 36''. Can 

 water in the depths below flow from the mild climate of the 

 temperate zones to the severer climates of the frigid zone without 

 falling below 36° ? To what, in the depths of the sea, can a 

 warm current of large volume impart its heat ? The temperature 

 of sea water from the tropics in which ice is forming is invariably 

 (§ 442) 28°. Does not the circumstance of De Haven's invariably 

 finding this to be the temperature below the ice on which he 

 drifted tend to confirm the conjecture (§ 479) about the ice and 

 the river water ? 



484, It comes to the surface. — This under polar cuiTent water, 

 then, as it rises to the top, and is brought to the surface by the 

 agit-ation of the sea in the arctic regions, gives out its surplus 

 heat to waim the atmosphere there till the temperature of this 

 warm under current water is lowered to the requisite degree for 

 going out on the surface. Hence the water-sky of those regions. 

 And the heat that it loses in falling from its normal temperatui^e, 

 be that what it may, till it reaches the temperature of 28°, is so 

 much caloric set free in the polar regions, to temper the air and 

 mitigate the climate there. Kow is not this one of those modifi- 

 cations of climate which may be fairly traced back to the efiect of 

 the saltness of the sea in giving energy to its circulation ? More- 

 over, if there be a deep sea in the polar basin, which serves as a 

 receptacle for the waters brought into it by this under current, 

 which, because it comes from towards the equatorial regions, 

 comes from a milder climate, and is therefore warmer, we can 

 easily imagine why there might be an open sea in the polar 

 regions — why Lieutenant De Haven, in his instructions (§ 428), 

 was directed to look for it ; and why both he and Captain Penny, 

 of one of the English searching vessels, and afterwards Dr. Kane, 

 found it there. And in accounting for this polynia, we see that 

 its existence is not only consistent with the h^'pothesis with 

 which we set out, touching a perfect system of oceanic circulation, 

 but that it may be ascribed, in a great degree at least, if not 

 wholly, to the effect produced by the salts of the sea upon the 

 mobility and circulation of its waters. Here, then, is an ofifico 



