— 64 — 



est water in the whole of the North Sea (including the Channel and the 

 Skagerak) is found along the coasts of Belgium and Holland, where the temp- 

 erature rises above 17 — 18°. From here the temperature decreases north- 

 wards, being thus at the surface, between Scotland and the Shetland Islands, 

 only 11°, while the surface temperature along the Norwegian coast of the 

 North Sea is abt. 14° The bottom temperature in the greater part of the 

 open North Sea north of the Dogger Bank is even in August below 7°, and 

 does not reach its maximum until in or about November. By way of example 

 the following table, for the region between 56° and 57° N and 2° and 4° E 

 for the period August 1902 — May 1907, may be given. 



The regular annual variation of the bottom temperature is thus quite 

 small, nor are its accidental changes great. Of the 37 records employed for 

 the above mean figures for the bottom, the lowest is 5,12° in May 1906 and 

 the highest 8,54° in November 1905; the total variation being thus scarcely 3^/2°. 



c. Conditions of current. 



The continued hydrographical measurements instituted by the inter- 

 national organisation in the North Sea from 1 — 14 June 1911 have greatly 

 increased our knowledge of the tidal currents of this region of the sea. 



The maxima of the M^ currents are very small in the Skagerak: under 

 4 cm/sec. And as long as one keeps to the open sea, or in any case, to deep 

 water, the Mg maxima are not particularly strong, even in the true North 

 Sea, nor is there any great difference between the maximal forces of current 

 at the bottom and at the surface. The weakest currents are of 8 — 9 cm/sec. 

 (in the north eastern part of the North Sea, at the edge of the Norwegian 

 Channel) the strongest of 27 — 36 cm/sec. (north-east of Newcastle and south 

 east of the Dogger Bank). As soon, however, as one comes in on to the 

 shallow coastal banks, the surface speed is essentially increased, and a very 

 considerable difference makes its appearance at the same time between the 

 maximal speeds of the surface and the bottom water. Thus, at Smith's 

 Knoll, a maximal current of 90 cm/sec. was found at 5 — 10 m., and only 

 35 cm/sec. at 40 m. At the mouth of the Channel however, the narrowing 

 of the waterway renders the currents stronger also at the bottom, and at 

 Varne 106 cm/sec. was found at 5 m. and 82 cm/sec. at 25 m. The Sg cur- 

 rents produced by the sun reach only in certain places 1/3 of the Mg maximum 

 while at other places the Sg maximum is not even i/^, of the M2 maximum. 



