OCEANIC CURRENTS. 



43 



currents the water is thoroughly mixed up, and the finer sediments 

 prevented from settling. In ocean-currents the conditions are as favor- 

 able for subsidence as in still water. It is evident, therefore, that sedi- 

 ments carried by ocean-currents must in a little time sink out of sight, 

 although from the great depth of these currents they may still be car- 

 ried to considerable distances. Deep-sea deposits have until recently 

 received little attention, although they are acknowledged to be of the 

 greatest geological importance. 



Submarine Banks. — These are usually accumulations of material 

 dropped by currents. They are formed under conditions similar to 

 those which determine the formation of bars ; i. e., either by the meet- 

 ing of opposing sediment-laden currents or else by such a current coming 



Fig. 35.— Tides of the German Ocean. 



The curved lines represent successive positions of the ad- 

 vancing tide. 



in contact with still water. In fact, the outer bar is a true submarine 

 bank. The currents may be either tidal or oceanic or river. Admira- 

 ble examples of both those modes of formation are found in the Ger- 

 man Ocean. The tidal wave from the Atlantic strikes the British Isles, 

 passes round in both directions, and enters this ocean from the north 

 around the north point of Scotland, and from the south through the 



