478 SCIENCE PROGRESS 



a very narrow one, and though the depth is the greatest in the 

 British sea-area, very little of a true current sets in through 

 this channel. The sea-bottom is shallow between Islay and 

 the north coast of Ireland, and forms a " barrier " which impedes 

 the flow of the Atlantic water. The Irish Sea is therefore a 

 relatively low-salinity area, and at no place does the proportion 

 of total dissolved salts exceed about 34/5 per thousand. Further, 

 there is a comparatively high rainfall off the coast of Ireland 

 and the north-west coasts of England. Nevertheless, the pulse 

 of the Gulf Stream periodicity can be felt distinctly in this part 

 of the sea ; and it has been possible to trace variations in the 

 salinity of the Irish Sea, along a line between Holyhead and 

 the Isle of Man, which are to be referred to the annual variations 

 in the strength of the Gulf Stream drift. The salinity of the 

 water is at a maximum here about February to May. 1 



The Norwegian Stream flows round the north of Scotland, 

 mainly between the Shetland Islands and the Faeroes. The 

 inflow to the North Sea between the Shetlands and the Scottish 

 mainland may be neglected. The drift afterwards turns round 

 to the south, flowing down the east coast of Scotland, and then 

 tends to the east and across to the Continental coast into the 

 Bight of Heligoland. Then, reinforced by a flow of coastal 

 water, and by an outflow from the Baltic, it turns to the north 

 and west again. Thus there is a cyclonic circulation in the 

 northern part of the North Sea — as is to be seen from fig. 2. 

 The figure shows that by far the greatest part of the water 

 entering the North Sea comes in from the north, and that the 

 contribution from the English Channel is so small that it may 

 usually be neglected. Tongues of truly Atlantic water may 

 project into the North Sea from both the north and south, but 

 the greatest part of this sea-area is covered with water of 34/5 

 to 347 salinity. 



We can hardly speak of these water-movements in the 

 shallow seas as "currents" in the true sense of the word. 

 Movements of water in these areas are mainly produced by 



1 The salinity changes in the water of the Irish Sea have been investigated by 

 the Irish Department of Agriculture and Technical Instruction, and by the Lan- 

 cashire Sea Fisheries Committee. See Bassett, Annual Reports of the Lancashire 

 Sea Fisheries Laboratory for 1907 and 1908 ; and Herdman & Scott, ibid. 1908. 

 The Irish results are published in the Bulletins of the International Council for 

 the Exploration of the Sea. 



