The Currents 

 J. C. Swallow 



The most impressive of tlie world's currents 

 is ttie Gulf Stream, stiown above on a ctiart 

 prepared by Governor Pownall in 1787. Its 

 volume transport is more than a thousand 

 times that of the Mississippi River. 



There are about three hundred million cubic miles of water in 

 the oceans, and all of it is moving about. The water is moving in 

 many different ways; in shallow water the waves move back and 

 forth every few seconds, and the tidal streams ebb and flow twice 

 a day. Currents, which are set up by the drag of the local wind on the 

 sea, vary with the changes in the wind itself. Besides these fluctuat- 

 ing movements there is, almost everywhere, a prevailing current, 

 just as in the atmosphere prevailing winds exist, although large and 

 frequent fluctuations can occur. Around the shores of the British 

 Isles the prevailing currents are weak compared with the tidal 

 streams, and careful observation is needed to reveal the resultant 

 flow of water along the EngUsh Channel into the North Sea, and 

 through the Irish Sea from south to north. 



In some parts of the oceans, though, the average currents are 

 more conspicuous. The Spaniards soon noticed the Gulf Stream in 

 their exploration of the West Indies, and early in the sixteenth 

 century Spanish ships were making good use of the prevailing 

 currents to aid their passages, keeping well to the south in the 

 Equatorial Current on the outward journey, and returning part of 

 the way to Europe in the northeastward flowing Gulf Stream. 



In deep water, far from land, a sailor can often detect a current 

 only by the discrepancy between his observed position and that 

 reckoned from his ship's course and estimated speed. Did Necho 



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