98 FRIDTJOF NANSEN. M.-N. Kl. 
which the bottom-water could be cooled down to —0'8? C. and —o'g? C. 
would be by contact with the overlying cold water-stratum. But along 
the *Fram's” route the cold bottom-water was separated from the cold 
top-layer by an intermediate warmer layer 600 or 700 metres thick, 
where the temperatures were above zero. It seemed very difficult to 
understand that in the still unknown parts of the basin there could be 
such entirely different conditions, that the whole bulk of thick warm 
water could be cooled down to —0'8* C. merely by contact with the 
overlying layer of cold Polar water, and that in this unknown region, 
the temperature would, from the surface to the bottom, at all depths be 
below —08 C. This cooling could not, to any great extent, be caused 
by intermixture with the overlying less saline strata, for the salinity 
would be thus too much reduced. It seemed extremely difficult to con- 
ceive, that such a great bulk of water, so well protected against cooling 
by direct radiation from the surface, by an overlying lighter water- 
stratum, could be so much cooled down chiefly by convection. It would 
seem to require a quite unreasonable length of time. 
Nevertheless no other explanation was apparent!; since the salinity, 
as also the temperature, was too high to make it seem likely that this 
bottom-water could have come from the Norwegian Sea. But the more it 
is considered the greater appears the difficulty in understanding how the 
bottom-water of the North Polar Basin can actually be cooled down to 
—0'8° C. and —o0:9" C. while under a thick protecting cover of lighter cold 
Polar water; it seems utterly impossible?. If, therefore, there be any 
possibility, in spite of the determinations, that the salinity of the bottom- 
water is as low as about 34°93 Yon it would be a much simpler and 
more probable explanation to assume that the bottom-water of the North 
Polar Basin, is formed in the same region as the bottom-water of the 
Norwegian Sea; further, that it flows thence into the North Polar Basin, 
underneath the intermediate warmer layer, just as it flows along the 
bottom southward into the southern part of the Norwegian Sea, and is 
slowly heated on the way by the subterraneau heat of the Earth as well 
! Oceanography of N. P. Basin, pp. 337 ef seq. 
? Prof. Pettersson (Geogr. Journ. vol. XXIV, pp. 318, 320) has adopted the writer’s 
previous theory that the cold bottom-water of the North Polar Basin is originally water 
of the intermediate warmer layer which has been cooled down to a lower temperatures; 
and he thinks that this cooling might be effected by melting of ice. Even if the ice 
did melt in the North Polar Basin in the manner assumed by Pettersson, which it does 
not (the ice is there always growing thicker from one year to another), his theory is im- 
possible because there are no ice-bergs in the North Polar Basin, and the polar ice is 
much too thin to reach down into the warmer water-strata underlying the thick layer 
of lighter Polar water. 
