214 PHYSICAL AND DIOLOGICAL CONDITIONS IN THE NORTH SEA. 



opposite the entrance of the Baltic, and an isolated patch between East 

 Anglia and the Dutch coast. The rest of the North Sea is covered by 

 North Sea water, except a narrow edging along the continental coast 

 extending some distance into the Skagerack ; this is coast water. The 

 isothermals, or lines of equal temperature of the surface water, are 

 interesting at this period. At the western entrance of the English 

 Channel we have 12° C, which diminishes as we pass up the Channel, 

 but the limit of 9° C. passes from the islands outside the Zuyder Zee to 

 a point on the English coast about Flamborough Head. North of this 

 we have only 8° and then T, a band of the latter extending from about 

 Aberdeen to the Baltic and along the Norwegian coast, while north-west 

 of this we have again 8° and 9°. Along the whole of the western coast 

 of the British Islands, the Atlantic temperature is 9° and 10°. The 

 influence of this distribution of temperature alone, on the distribution 

 of southern species of animals, cannot, I think, be over-rated, as will be 

 seen below when the distribution of animals is considered. The distri- 

 bution of animals is not discussed at all by Dickson in the paper with 

 which we are now dealing. 



In August, 1893, the northern tongue of oceanic water is broader and 

 extends further southward, reaching to the edge of the Dogger Bank, 

 while in the south a tongue from the Straits of Dover extends to the 

 latitude of Lowestoft. The band of coast water along the German and 

 Danish coasts is somewhat broader, but it does not extend into the 

 Skagerack ; we now see the Baltic current or stream flowing out in full 

 force, extending northwards along the Norwegian coast in a broad band. 

 This Baltic water is now, owing the influence of the sun on the land, of 

 higher temperature than any other part of the surface of the North Sea, 

 except two isolated patches near the British coasts. The whole of the 

 North Sea (surface) is now as warm as the Atlantic water on the west 

 coasts of the British Islands. Both in the North Sea and on the west 

 coasts, the temperatures diminish from south to north from 18° to 13° C, 

 but a narrow tongue of colder temperature extends southward, so as 

 to include the Orkney and Shetland Islands and part of the Moray 

 Firth. 



In November, 1893, the northern tongue of oceanic water is broader, 

 but does not extend further south ; the southern tongue extends a little 

 beyond the Texel. The outflow of the Baltic stream has ceased, and 

 coast water is seen in the map extending along the south-west coast of 

 Norway and entering the Skagerack, in the manner previously described 

 by Pettersson. 



The temperature of the surface water is now lowest in a band along 

 the coast of Holland, Germany, and Denmark, corresponding closely with 

 the extent of the coast water, where it is 8°. This same temperature 



