366 Alf Trolle. 



in good agreement with our observations on the sledge journeys, on 

 which both in November 1906 and December — January 1907/08 — 

 thus in the middle of winter — we saw large, open channels, which 

 indicated much movement among the drift-ice off Shannon Island, 

 whereas at the same time the ice off Maroussia lay fast and immov- 

 able. 



Average density of the Polar Current. 



Station IX (Åkerblom) Depth 0—300 m 1.02746 



— VII — — 0-200 - .... 1.02763 



The average density is thus somewhat greater here than in Sect. 

 Ill, but, as there, is greatest in the centre of the Current. 



This increase in the average density (which may indeed be due 

 to variation from year to year) may be caused by the Current flowing 

 over a comparatively shallower bank, which would lead to the heavier 

 bottom-water being raised somewhat and mixed with the overlying 

 layers. This is also suggested by the fact, that the 0° isotherm lies 

 higher here than in the more northerly section. 



i. The series from stations in the Greenland fjords. 



a. Entrance to Oresund. Series XI, XIII— XVI, XVII, XX— XXXVI, 

 XXXIX, XLII, LX A and В, LXII— LXIX, LXXII. 



Introduction. 



The station, at which the main portion of the investigations at 

 different seasons were made, lay in the mouth of Øresund, ca. V2 km. 

 from a small, rocky island on the outer coast called Maroussia (see 

 PI. XIV), where a depot was formed with provisions and instruments. 

 It will be seen from PI. XIV, that the station lay in a comparatively 

 deep channel (depth 150 — 200 meters); to the west was a part with 

 shallower water (depth 50 — 75 m.), which was called the bar or bar- 

 rier, the inflowing water-masses being dammed up here. 



The situation of the station satisfied the necessary conditions 

 for obtaining a valuable series of hydrographical observations. There 

 was sufficient depth (158 m.) to reach down to the warmer layer below 

 the temperature minimum and there was free circulation of the water- 

 masses in the sea down to this depth, as Øresund was not shut off 

 by submarine ridges east of the station. 



All the series were taken at the same place in a tidal fissure in 

 the fjord-ice, which extended in the direction towards Sonja Havn 

 and which was open in both winters 1906 — 07, 1907 — 08. Only a few 

 of the last series in 1908 were taken further in Øresund. 



During the first winter 1906 — 07 a number of series were taken 

 in the dark period of the year, and we succeeded in obtaining water- 



