THE ARCTIC SEAS. 57 



able breadtli, would be insufficient to prevent its total congelation, if it Aveve 

 not assisted by other physical causes. A magnificent system of currents is 

 continually displacing the waters of the ocean, and forcing the warm floods of 

 the tropical regions to wandey to the pole, while the cold streams of the frigid 

 zone are as constantly migrating toward the Equator. Thus we see the Gulf 

 Stream flowing through the broad gateway east of Spitzbergen, and forcing 

 out a return current of cold water to the west of Spitzbergen, and through 

 Davis's Strait. 



The comparatively warm floods which, in consequence of this great law of 

 circulation, come pouring into the Arctic seas, naturally require some time 

 before they are sufficiently chilled to be converted into ice ; and as sea-water 

 has its maximum of density, or, in other words, is heaviest a few degrees above 

 the freezing-point of Avater, and then necessarily sinks, the whole depth of the 



OPEN WATEa 



sea must of course be cpoled down to that temperature before freezing can 

 take place. Ice being a bad conductor of heat, likewise limits the process of 

 congelation ; for after attaining a thickness of ten or fifteen feet, its growth is 

 very slow, and probably even ceases altogether ; for when floating fields, or 

 floes, are found of a greater thickness, this increase is due to the snow that 

 falls upon their surface, or to the accumulation of hummocks caused by their 

 collision. 



Thus, by the combined influence of these various physical agencies, bounds 

 have been set to the congelation of the Polar waters. Were it otherwise, the 

 Arctic lands would have been mere uninhabitable wastes ; for the existence of 

 the seals, the walrus, and the whale depends upon their finding some open Ava- 

 ter at every season of the year ; and deprived of this resource, all the Esqui- 

 maux, whose various tribes fringe the coasts in the highest latitudes hitherto 

 discovered, would perish in a single Avinter. 



If the Arctic glaciers did not discharge their bergs into the sea, or if no 

 currents conveyed the ice-floes of the, north into loAver latitudes, ice Avould be 



