OCEAN CURRENTS 123 



fierce heat of the sun. It has been estimated that 

 in the tropical Atlantic alone the amount of water 

 raised annually would represent a cube of nearly 

 thirty miles in extent, or about 120 trillions of cubic 

 yards. Of course, an immense amount of this fresh 

 water falls back again into the ocean from whence 

 it has been raised, but the bulk of it is carried into 

 seas beyond the tropics and over the adjacent lands. 

 Now, to fill the great void thus caused, the colder 

 and heavier waters of the Arctic and Antarctic regions 

 continually flow in because they are continually being 

 augmented by rain and melted ice. In their motion 

 towards the equator they are assisted by the Trade 

 Winds from the north-east in the Northern hemisphere 

 and the south-east in the Southern hemisphere, and 

 thus they heap up the tropical warm water about the 

 equator. To escape to its level, which of course all 

 water must do, this immense volume of warm water, 

 pressed on either side by the heavier cold banks of 

 water, takes the line of least resistance, which is 

 directly westward. Two main causes decide this : 

 first, the movement of the earth upon its axis from 

 west to east, and secondly, the easterly winds on both 

 sides of it. There is another adjunct which we will 

 come to directly, but at present it is sufficient to 

 indicate the two main forces. 



Now, this mighty body of water, twelve or fifteen 

 hundred miles wide, flows steadily westward, slowly, 

 it is true, but with a quite perceptible rate of from 

 six to twenty-five miles a day, according to the 

 season. It enters the Gulf of Mexico, washing the 

 shores of the Antilles, but in no ;wise hindered by 

 them. It flows ;majestically westwards into the Griilf, 



