THE GULF STREAM. 203 



first theory, which assigns to the trade-winds the princi- 

 pal almost the sole agency in the generation of the 

 Atlantic current-system. He refuses indeed, to look 

 on the subject as one of any doubt or difficulty. ' The 

 dynamics of the Grulf Stream have of late,' he writes, 

 ' been made a subject of much (we cannot but think 

 misplaced) wonder, as if there could be any possible 

 ground for doubting that it owes its origin entirely to 

 the trade-winds.' ' If there were no atmosphere, there 

 would be no Gulf Stream, or any other considerable 

 oceanic current (as distinguished from a mere surface- 

 drift) whatever.' He presents his solution somewhat 

 as follows : The trade-winds are an actually existent 

 cause for an easterly motion in the tropical seas ; we 

 cannot ignore their action ; we know, also, that when 

 the trade-winds arrive at the equator, they have lost 

 their easterly momentum; and we know, therefore, 

 that that momentum must have been imparted to the 

 surface of the water (for where else can it have gone ?) ; 

 hence there arises the great easterly movement which 

 generates the whole system of circulation. 



The second view, which attributes oceanic circulation 

 to differences of temperature and saltness in different 

 parts of the ocean, is supported by Humboldt and others, 

 but is taken up most unflinchingly by Captain Maury, 

 who assigns it as practically the sole cause of all oceanic 

 circulation. 6 The Grulf Stream,' he writes, ' as well as 

 all the constant currents of the sea, is due mainly to this 

 cause. Such differences are inconsistent with aqueous 

 equilibrium, and to maintain this equilibrium the 



