THE NORTHERN SEAS. 87 



the basin, about 10,000 feet. The course of the marine 

 currents near the mouths of the Nile is from west to 

 east. The action of these currents, it is hardly neces- 

 sary to say, tends to carry the alluvial matter east- 

 ward ; hence the deep part of the sea is farther from 

 the coast eastward from the Nile than westward. 



If we ascend from this basin to the north-west, we 

 shall find ourselves among the rocky gorges domi- 

 nated by Candia and Scarpanto. These irregular and 

 broken elevations form a great volcanic region, the 

 principal peaks of which form the islands of the Greek 

 Archipelago. 



The defiles of the Dardanelles, the valley covered 

 by the Sea of Marmora, and the ravine commanded 

 by Constantinople and Scutari, open to the plain upon 

 which debouch the greatest rivers of Europe. The 

 Black Sea is of little depth. It is surrounded on its 

 southern shores by the heights of the Caucasus, the 

 Armenian mountains, and the Balkan. Northward 

 the Kussian steppes extend under the sea, which their 

 debris, waslied down by the great rivers, tend to fill up. 



G. The Baltic— The North Sea— The Straits of Dover— The 

 English Channel— The Bay of Biscay. 



The Baltic, like the Black Sea, is of little depth. 

 We shall see by-and-by that its bed is the seat of 

 very remarkable phenomena. Its northern part is 



