£6 PHYSICAL GEOGRAPHY OP THE SEA. 



retard the flow of rivers, and thus it is to be expected that con- 

 tinuous winds, even of moderate strength, must have a tendency 

 to impel the waters in the same direction. 



The steady trade-winds of the tropical zone, and the prevail- 

 ing westerly winds in higher latitudes, consequently unite their 

 influence with that of the above mentioned causes, in driving 

 the waters of the tropical seas to the west, and those of the 

 temperate zones to the east. 



The tides also, which on the high seas generally move from 

 east to west, promote the flow of the ocean in the same 

 direction, and thus contribute to the westerly current of the 

 tropical seas. 



Nor must we forget that the obstacles which the ocean- 

 currents meet on their way ; such as intervening lines of coast,, 

 sand banks, submarine ridges, or mountain chains, have a great 

 influence upon their course, and may even give them a dia- 

 metrically opposite direction to that which they would otherwise- 

 have followed. 



Having thus briefly mentioned the origin and causes of the- 

 currents, which intersect the seas like huge rivers, I shall now 

 describe such of them as are most important and interesting in 

 a geographical point of view. 



In the northern part of the Atlantic, between Europe, North 

 Africa, and the New World, the waters are constantly perform- 

 ing a vast circular or rotatory movement. Under the tropics 

 they proceed like the trade-winds from east to west, assisting 

 the progress of the ships that sail from the Canaries to South 

 America, and rendering navigation in a straight line from Car- 

 thagena de Indias to Cumana (stream upwards) next to im^ 

 possible. This westerly current receives a considerable- addition 

 from the Mozambique stream, which, flowing from north to 

 south between Madagascar and the coast of Caffraria, proceeds 

 round the southern extremity of Africa, and after rapidly ad- 

 vancing to the north, along the western coast of that continent,, 

 as far as the island of St. Thomas, unites its waters with those 

 of the equatorial current, and continues its course right across 

 the Atlantic. In this manner the combined tropical streams 

 reach the eastern extremity of South America (Cape Koque),. 

 where they divide into two arms. The one flowing to the south, 

 follows the south-eastern coast, and gradually takes a south- 



