224 The American Geologist. ^i"''- ^'-^^^ 
ence to about 70 metres below the present followed. A 
third elevation raised portions of the sea bottom so that 
the glacial deposits were incised by new channels, now 
forming some of the submerged valleys. Again a third 
depression brought the land down to 21-22 metres, 
after which it rose to the present hight. (pp. 34-35). 
Xansen finds a remarkable repetition of changes which the 
reviewer has shown as occurring on this side of the At- 
lantic. 
In the American archipelago, Nansen calls attention to 
depths of 411,512 and more than 732 metres, as well as 
shallower ones, indicating that the region is one of typical 
fjords with channels opening into the Polar basin, though 
they may be found obstructed as in the case of the Nor- 
wegian fjords ; and he further considers that the Arctic 
basin is not very distant. 
Even Avithout soundings on the American shelf to 
show its limit, Nansen says "the Fram cannot have drifted 
along a deep and narrow sub-ocean channel." He espec- 
ially mentians that the existence of the cold bottom water 
makes it "perfectly impossible." The heavy bottom water 
at more than 800-900 metres, originating from the inflowing 
Atlantic, cannot have been cooled down at the observed 
depths, beneath the overlying warmer water, and the lower 
layers, alTected by subterranean heat ; it must have cooled 
down somewhere in the unknown portion of the Polar 
basin, in contact with the surface layer of cold water — this 
at some place far off from the course of the Fram. Similar 
conditions exist in the Norwegian sea, where, however, the 
centre of cold surface w^ater has been found north of Jan 
Mayen. In the Polar basin, Nansen locates the centre of 
cold surface water somewhere between the North Pole and 
Bering strait; but the bottom water is not reduced to quite 
so low a temperature as in the Norwegian sea. According- 
ly "we are obliged to assume that it (the deep basin) has 
a wide extension," probably the greater part of the still un- 
known Polar region (p. 228). Finally the drift of the ice, 
imder the east coast of Greenland, is much greater than 
farther north, where the ice belt must correspond to the 
broader one in the known and unknown Polar sea, from 
Avhich it converges. 
