— 60 — 



the bottom as at the surface, but north of Lat. 56° N the conditions are 

 very different, the bottom Isohahne now turning towards the north east in 

 to the mouth of the Skagerak, running here close along the coastal bank of 

 Jutland, past the mouth of the Kattegat, and may practically be said to 

 disappear at the mouth of the Christiania Fjord. Along the whole of the 

 Norwegian coast of the Skagerak and North Sea the bottom water is appreci- 

 ably more than 34Va''/oo salt. 



If we look at the surface, going from the 34,5 "/oo Isohaline in towards 

 land, the salinity sinks fairly rapidly in the inner portion of the German Bight 

 and for the greater part of the surface of the Skagerak it is 32 "/qo. Outwards 

 however, towards the central part of the North Sea, the salinity increases but 

 slowly; the highest salinities found in the interval between the eastern and 

 western 84,5 "/oo Isohaline lie, both for the bottom and the surface, between a 

 minimum of abt. 34,75 "/qo at Lat. 54° N (due south of the Dogger Bank) and 

 two maxima of fully 35,2 "j^o, the one in the Straits between Dover and 

 Calais, the other in the sea to the north-east of Scotland, both maxima are 

 produced by inflow from the Atlantic. If we pass through the Channel out 

 towards the Atlantic Ocean, the salinity increases continually, and in the 

 western mouth of the Channel, both at the surface and at the bottom, salinity 

 is in places as high as 35,4 "/oq. 



In the southern part of the North Sea, south of Lat. 54° N, and west 

 of Long. 5° E, the water column at any point in the open sea has almost 

 exactly the same salinity from surface to bottom; this is moreover true not 

 only of the mean salinities, but also with so close approximation for the 

 individual measurements, that it is possible in these waters to follow, in the 

 main, the alterations in the salinity of the masses of water by the aid of 

 surface observations alone. The same is true of a great part of the Channel, 

 but north of the Dogger Bank the conditions are different. In the Skagerak, 

 the salinity may rise from below 28 */oo at the surface to over 35 "/oo at 

 bottom, and even in the outer part of the Norwegian Channel the salinity 

 varies from abt. 83 "/„q at m. to over 35,1 %„ at the bottom. In the open 

 waters of the northern North Sea, the differences between surface and bottom 

 salinities are, it is true, much less, only fractions of 1 "/ooj but these apparently 

 small differences are of such importance to the question of whence the masses 

 of water come, and for the hydrographical conditions as a whole, that it will 

 always be necessary to take series throughout the whole sea from surface to 

 bottom. 



The International Investigations have shown with certainty, that the 

 average annual variation of salinity in great parts of the North Sea is less 

 than 0,2 "/qq, and in by far the greatest part of this sea district less than 



