OCEAN CURRENTS 



OF all the means whereby the mighty ocean, regarding 

 it as a whole, exercises its beneficent influence upon 

 the earth, none are more potent in their power, more 

 wide-reaching in their effects, or more interesting to 

 study than those enormous movements of incalculable 

 masses of water which we call " currents " and " tides." 

 Now, at the outset of what must be, in the nature of 

 things, but a cursory glance at these immense oceanic 

 phenomena, it is entirely necessary to point out the 

 difference between current and tide. As briefly and 

 roughly as possible, a current is like the movement 

 of a stream which has a slight alteration in its level 

 from its source to its mouth. It runs in the one 

 direction because water cannot run uphill, it runs 

 faster or slower according to the quantity of rain 

 that falls, and sometimes, when the rainfall has been 

 excessive, it overflows its banks and makes a series 

 of temporary currents wandering over the adjacen 

 country, their direction being determined entirely by 

 the variations in the contour of the land. But, in 

 general, the direction of such a stream is quite per- 

 manent, owing to the physical confinement of its 

 banks, and therein it differs much from an ocean 

 current. The parallel is, however, sufficiently near 

 for our present purpose. 



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