38 THE BOTTOM OF THE SEA. 



slowly but steadily rising, insomuch that the Gulf 

 of Bothnia diminishes in extent and depth at a 

 certain constant rate. At the same time, the southern 

 part of this ocean-bed is sinking, and the sea is 

 gradually taking possession of the lower plains of 

 Mecklenburg and Pomerania. 



The Skager Kack leads from the Baltic into the 

 North Sea, which is likewise of slight depth. Ex- 

 cepting a long narrow trough which follows the 

 direction of the coast of Norway, the bed of the 

 North Sea may be described as an undulating plain, 

 never more than 600 feet deep. Some of the greater* 

 banks almost reach the level of the waters ; others 

 are not more than a hundred feet beneath the surface. 

 In this sea various kinds of fish are abundantly 

 nourished by marine worms ; numerous sites covered 

 with algae provide them with an agreeable retreat ; 

 and the water, constantly beaten by the winds, is 

 plenteously supplied with air for the respiration of 

 its innumerable hosts. 



The shores of the British Isles are very abrupt, but 

 the sea is of no great depth until we pass beyond the 

 west of Ireland and the Hebrides. At the distance 

 of about twenty leagues from Valencia we find a 

 depth of 600 feet, which increases westward, until 

 we arrive at the Telegraphic Plateau already do- 

 scribed. 



