98 THE OCEAN RIVER 



slow. Man is not naturally a seagoing animal, and he has been 

 able to live for extended periods on the surface of the ocean 

 only by the invention and development of artificial aids in 

 the form of simple floats, sailing vessels, and later of more 

 elaborate mechanically propelled seagoing hotels. It is a rela- 

 tively simple matter to take measurements and observations 

 on the rigid platform of land; but to do this on the heaving 

 deck of a small vessel at sea is a very different affair. The prob- 

 lem of measuring and observing the ocean at first hand is 

 neither a simple nor comfortable exercise, even in today's 

 fast and seaworthy vessels. Hence our knowledge of the Gulf 

 Stream, of the Atlantic current system of which it is a part, 

 and of the forces setting them in motion, has only in recent 

 years made rapid progress. 



The great Ocean River is, in essence, a vast circular swirl 

 of water complicated by the inflow and outflow of counter- 

 currents, eddies, tributaries, and branches. North of the 

 equator in latitude 15° N. the north equatorial current, 

 under the whip of constant trade winds, runs in a westerly 

 direction toward the American continent, and would thus 

 girdle the globe if it were not turned and channeled by the 

 interposed continents and spun clockwise by the earth's rota- 

 tion. 



The wind starts westward off the African coast behind which 

 lies the great Sahara, and so the waters begin to move by the 

 Canaries and Cape Verde Islands in a great wide flow. Then 

 the west-driving current as it accumulates in its ocean passage 

 is forced in a northerly direction and in a clockwise motion 

 north of the equator. South of the equator is another west- 

 ward-flowing current, and this spins south and to the left, 

 for in southern latitudes the earth's rotation works contrari- 

 wise. We spoke of continental interference. The west-driving 

 south equatorial current only in part turns into the southern 

 gyre. The huge shoulder of Brazil acts as a baffle which 



