OCEAN CURRENTS 175 



effect could only be due to whatever difference remained. 



James CroU (1870), the Scottish geologist, was the first 

 to criticize Maiu^y's theory and to show that his causes 

 were inadequate and contradictory. W. B. Carpenter in 

 1870 advanced the view that the Gulf Stream was only a 

 special case of the general oceanic circulation due to cooling 

 and sinking at the poles and heating at the tropics. Wyville 

 Thomson, in the Depths of the Sea (1872), disputes this, and 

 reverts to Sir John Herschel's opinion (1846) that the heat- 

 distribution of the North Atlantic is due to the Gulf Stream, 

 and that that current is mainly caused by the trade and 

 anti-trade winds. 



It is now known, however, that the Gulf Stream is not 

 an independent phenomenon, but is a part of the general 

 system of surface circulation of the ocean, a system in which 

 the currents (diverted to the east, as a result of the rotation 

 of the earth, in their course northwards from the equator) 

 flow clockwise in the North Atlantic around a central 

 relatively calm area, the Sargasso Sea, in which sea-weeds 

 and other floating objects accumulate. 



We have seen that the cause of the Gulf Stream can be 

 traced back to the great north equatorial current which 

 flows from east to west and forms the southern boundary of 

 the Sargasso Sea. This magnificent equatorial stream, 

 driven across the Atlantic by the trade-winds, conveys such 

 an enormous body of warm and relatively salt water into 

 the Caribbean Sea and the GuK of Mexico as to raise the 

 level of these seas by several inches above that of the 

 Atlantic, before emerging as the GuK Stream through the 

 narrow Strait of Florida at a temperature of 86° F. 



The officers of the United States Coast Survey have made 

 many hydrographic sections across the Gulf Stream area 

 from Havana, in the Gulf of Mexico, to Cape Cod, Massa- 

 chusetts, and we owe the most detailed modern information to 

 their work. When followed on its easterly course it is found 

 that the GuK Stream as a definite current or " river in the 



