286 



LEVEL OE THE OCEAN AFFECTED BY 



[Ch. XIII. 



there is open sea during part of the year at the pole itself, 

 and the observations of Eschricht and Bernhardt on the 

 migrations of the Greenland whale are rather confirmatory 

 of this idea. It appears that this northern whale, Balcena 

 Mysticetus, is different from the whale called B. Biscayensis, 

 a species now almost extirpated, and which once inhabited 

 the British seas and the Bay of Biscay. In winter the 

 Greenland whales accompany the ice when it floats farthest 

 to the south in Baffin's Bay, but in the summer, when the 

 ice is only to be found farther north, they migrate to parts 

 of the sea nearer the pole, having been seen as far north as 

 man has yet penetrated. Apparently they retreat to the 

 polar sea, which cannot therefore be covered by a continuous 

 sheet of ice, for in that case they would be suffocated, since 

 they must occasionally come to the surface to breathe. They 

 could, however, pass under considerable barriers of ice pro- 

 vided there were openings here and there ; and so they may 



more 



more 



The notion that we ought to find the ice continually increas- 

 ing in thickness as we approach the pole would hardly be 

 justified, even if the arctic land was so unbroken as to ex- 

 clude the interference of oceanic currents conveying water 



from 



latitudes. For observations on the 



Swiss glaciers have shown to what an extent those rivers of 

 ice are often lowered by evaporation, or by the passage of the 

 ice into a gaseous form, without its having passed through the 

 intermediate fluid condition. When certain dry winds blow, 



m 



we see the average number of inches of rainfall to diminish 

 constantly, though very irregularly, as we pass from the equa- 

 tor to the pole, so we may reckon on a diminution of the quan- 

 tity of snow and the prevalence near the pole of a dry air, 

 especially if there be snow-covered lands farther south inter- 

 cepting aerial currents blowing from warmer regions, and 

 causing them to part with their moisture in the 



form 



snow. 

 Mr, 



to 



I 









summer 



