— 30 - 



regions has increased during recent years amongst the biologists as well as amongst 

 others. Through the international investigations a much more detailed comprehension of 

 hydrography has been attained during recent years than was formerly the case. We are 

 able at present to say much more regarding the changes occurring in temperature and 

 salinity, especially concerning the North Sea. By means of the current-measuremehts 

 of recent years quite new facts have been brought to light, and these are of great im- 

 portance especially for our problems. The current-measurements to be mentioned here 

 were all made in close connection with the fishery investigations and throw light upon 

 these in essential points. 



A. Salinity and Temperature conditions in general 



1. Salinity at the Surface 



Fig. 2 shows the mean distribution of the salinity at the surface in the Norwegian Sea 

 and in the North Sea. So far as the North Sea is concerned, the Chart is based on 

 Knudsen's and Smith's charts in the international Procès-Verbaux (No. VI) and seems to 

 be trustworthy. With regard to the Norwegian Sea the accuracy is less, due to the fact 

 that in the winter half-year there was only opportunity for a few observations. This 

 Chart compared with the Current- Chart, fig. 3., shows quite clearly the nature of the 

 different water-layers; the principal characteristics will be well known from the literature 

 of recent years. Fig. 2 shows however some points which deserve more detailed dis- 

 cussion. We notice first of all , that the Faeroes and the Fseroe banks are washed by 

 the saltest Atlantic water. The water which passes the Fœroes and the Faeroe banks 

 forms later, as can be seen from the Charts, an integral part of the Gulf Stream in the 

 southern Norwegian Sea. The remaining Gulf Stream water, passing along the slope 

 west of Shetland, comes fairly directly from the northern Atlantic Ocean through the 

 Fseroe— Shetland Channel. Of this Atlantic Water one part enters into the North Sea, 

 mostly north round the Shetland Isles; we thus have two different directions of move- 

 ment over the Tampen, to a certain extent a division of the current: the main branch, 

 which proceeds as the Gulf Stream northwards along the Norwegian coast, and a smaller 

 branch, which bends in a southerly direction into the North Sea towards the coast of 

 Scotland. 



A second important circumstance noticeable on fig. 2 is, that we find so little mixed 

 water of between 34 and 35 °/oo salinity in the course of the Gulf Stream along the Nor- 

 wegian coast, whereas in the North Sea we find much of this mixed water ; here it covers 

 almost the greater part of the surface. Whilst the 34,7 and 35,0 isohalins generally run 

 quite close together, with but a very small surface between, the surface bounded by these 

 isohalins in the North Sea is very large. It appears clearly from the figure also, that a 

 distinct and well-marked cyclonic movement goes on in the North Sea, such that the 

 water which flows in a southerly direction along the east coast of Scotland and North 

 England and which consists partly of pure Atlantic water and partly of coastal water 

 from the west coasts of Scotland and Ireland, extends over the North Sea north of the 

 Doggerbank and towards the Skager Rak, and then with a further turn joins on to the 

 Baltic Stream. 



The coastal water along the Norwegian coast is mostly of a salinity under 34°/oo. 



