HYDROGRAPHICAL INVESTIGATIONS 207 



salinity of 30 to 32 per thousand. It flows out as 

 a surface current from the Skagerack along the 

 Norwegian coast. It is produced by the rivers 

 falling into the Baltic, and at certain seasons, owing 

 to rainfall and the melting of snow, land and sea 

 ice, its volume is enormously augmented. It is a 

 mixture of fresh water with the salt water which 

 enters the Baltic as a deep current. In addition 

 to these two contributory kinds of water, two 

 others may be present in North European seas, 

 which are : (3) North Sea water, with a salinity 

 of 34 to 35. At certain times in the year this 

 forms the greater part of the water covering the 

 surface of the North Sea. (4) Bank water. This 

 forms an edging of variable width along the con- 

 tinental coasts. It is relatively light, possessing a 

 salinity of 30 to 32 parts per thousand. Both 

 Bank water and North Sea water are mixtures of 

 the two original components, Atlantic and Baltic 

 waters. Finally, a certain quantity of Arctic water 

 may reach into the North Sea in some seasons. 

 This is cold water, and has a salinity of less than 

 35. It enters the North Atlantic as a deep 

 current.^ 



In May 1893 the waters of the North Sea had 

 the following arrangement ^ : — There was little 



1 See Pettersson, Scottish Geographical Journal for 1894, and 

 Hjort, Nordgaard, etc. 



2 Dickson's charts of the North Sea in 1893, published in the 

 Geographical lournaliox 1896, illustrate these changes very well. 



