THE ARRIVAL OF MAN IN EUROPE 



of the central Atlantic, both north and south 

 of the equator, gets carried into the northern 

 temperate zone. In this way the Gulf Stream, 

 coming northward up the west coast of Africa, 

 sweeps across the Atlantic to the easternmost 

 point of Brazil, where part of it gets deflected 

 southward toward the Antarctic Ocean, but most 

 of it flows northwesterly into the Gulf of Mex- 

 ico, whence it is deflected northeasterly toward 

 the European coast, giving to England its cli- 

 mate of perpetual spring in the latitude of Lab- 

 rador, and tempering the cold of the North Sea 

 even beyond the Arctic Circle. According to 

 Mr. Croll, the quantity of extra heat which the 

 northern hemisphere receives from this source, 

 over and above that which it would get simply 

 from direct solar radiation, amounts to fully 

 one fourth ofthe latter quantity. But when thJe 

 aphelion of the northern hemisphere occurred 

 in midwinter, along with a very high eccentri- 

 city, all this must have been changed. The 

 tendency of these circumstances, as we have 

 seen, was to make the northern hemisphere 

 very cold, while producing a perpetual srjring 

 in the southern hemisphere. Now, when once 

 the north pole had become colder than the south 

 pole, the northern trades would begin to blow 

 with greater force than the southern, until after 

 a while the neutral line between the two would 

 be shifted south of the equator, and, instead of 

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