4 8o SCIENCE PROGRESS 



resultants when the influence of the tidal streams is eliminated ; 

 or by experiments and observations of the course of floating 

 objects and wreckage. When the tidal streams are ignored 

 it is seen that there is a tendency for water to flow (i) round 

 the north of the Shetlands and down the east coast, and 

 across the North Sea, issuing from the latter as a stream 

 which flows along the Jutland coast in a northerly direction ; 

 (2) through the English Channel into the North Sea; and (3) 

 through St. George's Channel and the Irish Sea from south 

 to north. The direction of both the isotherms and the 

 isohalines shows that these water-movements do really occur. 



Fig. 1, which represents the course of the isohaline lines 

 in northern seas, 1 shows that the 35 per thousand isohaline 

 does not actually touch the shores of the British Islands, 

 but curves round the north of Scotland into the North Sea. 

 It also penetrates through the English Channel into the 

 latter area. The greater part of the North Sea itself is filled 

 with water which is less than 35 per mille. salinity, and there 

 is usually an indication of an " island " of truly Atlantic 

 water in its central part. (See fig. 1.) 



Fig. 2 shows the further course of the Norwegian Stream 

 in high latitudes. The water-circulation in these parts of 

 the northern ocean is very complex, because of the existence 

 of a multitude of large and small eddies, mainly cyclonic in 

 direction. The factors governing it are (1) the relatively 

 strong north-easterly Norwegian Stream, and (2) the southerly 

 flowing East-Icelandic Polar Stream. A number of submarine 

 banks extend across from the British Plateau to the coast of 

 Iceland, and the Faeroese Islands are the most elevated points 

 of these. Between the latter islands and the Shetlands is a rela- 

 tively deep channel, interrupted by a rather narrow elevation, 

 the well-known Wyville-Thompson Ridge : over this ridge 

 the water is from 500 to 600 metres in depth, and on either 

 side of it the sea-bottom slopes down to about 3,000 metres 

 in a comparatively short distance. The Norwegian Stream 

 flows through this channel and over the ridge, scouring the 

 surface of the latter free from any sediment. 



The main course of the southerly-flowing Polar Stream 



1 For a detailed account of the salinity and temperature of Northern Seas see 

 Bulletin Trimes/riel, Cons. Perm. Internat. Explor. Mer, Partie Supplementaire . 

 Copenhague, 1909. 



