— 40 — 



in the course of the year. In winter we find here everywhere the low coastal water 

 temperatures of about 4 — 5° and salinities of between 34— 35 °l^^. 



In summer the temperatures in this area are everj'where from 10 to over 16 °. The 

 salinities in summer were somewhat smaller, from 32 to about 35 °loo. 



We find here the same kind of great fluctuations as those already described previously 

 for the coastal water. It is specially striking that in summer we find in the North Sea north 

 of the Dogger in an intermediate depth of 40— 50 M., so to speak a continuation of the 

 Southern North Sea bottom. From the surface down to the depth mentioned we have 

 high temperatures as in the southernmost part, but in the bottom layers under 50 M. 

 we find in summer a truly winter condition with temperatures under 7°. In these 

 parts of the North Sea consequentlj^ we can distinguish between two quite different water 

 layers, an upper with large annual temperature variations and a lower where the tem- 

 perature is practically constant. 



The small variations found in the temperature of the bottom water show a minimum 

 temperature in summer and a maximum in winter. The salinities vary very little in the 

 whole region, least in the most northern part towards Shetland, where we have a salinity 

 of more than 35 "/^^ from the surface to the bottom the whole year through. 



The movements in the North Sea have already been briefly described above. We 

 may add that the velocity in the bottom water is probably very small in the northernmost 

 North Sea throughout the greater part of the year, with exception perhaps of in autumn 

 or winter, when the renewal of the bottom water chiefly takes place. 



As mentioned, the upper layers show a distinct cyclonic movement, which perhaps 

 explains the presence of the isolated 35 °l^^ water seen on fig. 2. The point where 

 35 °/oo stands isolated on the surface lies probably in the centre of the cyclone and is 

 thus not carried any further. Something similar appears in the deeper layers, as an 

 solated spot with temperatures under 6° can be noticed in the August section. 



The tidal currents are much felt over the entire North Sea, especially in the south- 

 ern part, where the tidal wave enters partly through the Channel partly from the north 

 along the Scottish and English coasts. 



On account of the strong ebb and flood movement the water layers in the southern- 

 most part of the North Sea are well mixed. Here in general the same temperatures 

 and salinities prevail from the surface to the bottom. 



The tidal currents are also very noticeable in the central and northern parts of the 

 North Sea. During the measurements on the Ling Bank in August 1906 they were found 

 to be much stronger than the average drift movement and were able to attain a velocity 

 of over 30 cm. per second (15 miles in 24 hours). On the day when these observations 

 were made, there was a mean drift on the surface of the Ling Bank in an easterly direc- 

 tion towards the Norwegian coast — somewhat more northerly at the bottom, ap- 

 proximately towards the north-east. The velocity was nevertheless small, 3 — 5 cm. per 

 second. 



