72 FRIDTJOF NANSEN. M.-N. KI. 
The only way in which these conditions can be explained, if the obser- 
vations be fairly correct, is by supposing that during the previous winter 
or spring there has been a vertical circulation in this region, reaching 
down to 200 or 300 metres; and if this vertical circulation could break 
trough the underlying warmer water with a higher salinity, the possi- 
bility of bottom-water also being formed occasionally in this region is 
not excluded. 
Ryders Station III (Å II, Pl. V) shows also some resemblance to 
his Stat. II: the temperature-minimum lies comparatively deep (at 94 
metres) and water with temperatures below —1° C. reaches down below 
180 metres from the surface. 
At Stat. 117 of the Ingolf Expedition (July 23, 1896, I 117, Pl. V) 
the cold surface layer has been very deep (—o'7° C. was observed at 
188 metres) and the underlying warmer layer has been comparatively 
thin (0°0° C. was observed at 377 metres); but the values of the sali- 
nities are evidently too high, as they give much too high densities1. 
North of Amundsen’s Stations, at Mohn’s Stat. 350 (M 350) and 
Kolthoff-Ostergren’s Stat. I. (Æ I), there are also indications of a vertical 
distribution similar to that of the North Polar Current and underlying 
water-strata (see Sect. IX, Pl. X). 
In the North Polar Basin, along the track of the “Fram”, the conditions 
were very much the same as in the case of the East Greenland Polar Cur- 
rent. The water of the upper temperature-minimum at 50 or 60 metres? 
1 The Station 217 of the Norwegian North Atlantic Expedition (July 27, 1877) in 71° o' 
N. Lat. and 5° 9‘ W. Long. seems to form a most remarkable excepition, if the 
temperatures given can be trusted; but as they were all taken with the Miller-Cassella 
Thermometers this may be doubtful. They give a minimum of —ı'8°C. at 55 and 
94 metres (the minimum thermometers may be expected to have given this temperature . 
correctly), and below this depth the temperature nowhere rose above —1'1? C. If this 
really be correct, it seems as if the region with bottom-water near the surface, 
has that summer extended so far south as towards this Station. That this may actually 
have been the case, might also be indicated at the nearest Stations 218 and 219, where 
temperatures of —o'9° C. and —1'1? C. are met with at 55 or even 37 metres. It may, 
however, be that this has only been a temperature-minimum of an upper layer of Polar 
water, whilst the Minimum and Maximum Thermometers have not been able to indicate 
the higher temperatures of the underlying, warmer water, as the sea-surface was 
covered by a warm water-layer of about 4 or 5° C. 
In writing ‘The Oceanography of the North Polar Basin’ it was assumed that the water 
of this temperature-minimum "must originate from other parts of the North Polar Basin, 
where the water near the surface has a similar salinity” (cf. op. cit., p. 323). It did not 
seem to appear probable that there was sufficient ice at depths between 50 and 70, 
or 80 metres, to cool the whole water stratum down to near its freezing point, and 
the distance between the great hummocks, reaching so deep, was thought to be too 
great to produce such a general effect. But, upon considering the question more 
closely, it must be concluded that an appreciable cooling of the water may be thus 
