364 POWER OF THE GULF-STREAM CHAP. xvm. 



by the united influence of which I still believe the principal 

 revolutions in the meteorological state of the atmosphere 

 at different geological periods have been brought about. The 

 Gulf Stream was particularly alluded to by me as moderating 

 the winter climate of northern Europe, and as depending for 

 its direction on temporary and accidental peculiarities, in 

 the shape of the land, especially that of the narrow Straits of 

 Bahama, which a slight modification in the earth's crust would 

 entirely alter. 



Mr. Hopkins, in a valuable essay on the causes of former 

 changes of climate,* has attempted to calculate how much 

 the annual temperature of Europe would be lowered if this 

 Grulf Stream were turned in some other and new direction, 

 and estimates the amount at about six or seven degrees of 

 Fahrenheit. He also supposes that if at the same time a con 

 siderable part of northern and central Europe were submerged, 

 so that a cold current from the arctic seas should sweep over 

 it, an additional refrigeration of three or four degrees would 

 be produced. He has speculated in the same essay on the 

 effects which would be experienced in the eastern hemisphere 

 if the same mighty current of warm water, instead of 

 crossing the Atlantic, were made to run northwards from the 

 Grulf of Mexico through the region now occupied by the valley 

 of the Mississippi, and so onwards to the arctic regions. 



After reflecting on what has been said in the thirteenth 

 chapter of the submergence and re-elevation of the British 

 Isles and the adjoining parts of Europe, and the rising 

 and sinking of the Alps, and the basins of some of the great 

 rivers flowing from that chain, since the commencement of the 

 glacial period, a geologist will not be disposed to object to the 

 theory above adverted to, on the score of its demanding too 

 much conversion of land into sea, or almost any amount of geo- 



* Hopkins, Geological Quarterly Journal, vol. viii. p. 56, 1852. 



