THE GULF STREAM. 37 



the other it is light. Between them the ocean intervenes ; but water 

 is bound to seek its equihbrimn as its level ; and here, therefore, 

 we unmask one of the agents concerned in causing the GuK Stream. 

 What is the power of this agent — is it greater than that of other 

 agents, and how much ? We camiot say how much ; we only 

 know it is one of the chief agents concerned. Moreover, speculate 

 as we may as to all the agencies concerned in collecting these waters, 

 that have supplied the trade-winds with vapom-, into the Caribbean 

 Sea, and then in driving them across the Atlantic — we are forced 

 to conclude that the salt which the trade-wind vapom- leaves be- 

 hind in the tropics has to be conveyed away from the trade- wind 

 region, to be mixed up again in due proportion with the other water 

 of the sea — the Baltic Sea and the Arctic Ocean included — and that 

 these are some of the waters, at least, which we see running off 

 through the Gulf Stream. To convey them away is doubtless one 

 of the offices which, in the economy of the ocean, has been assigned 

 to it. But as for the seat of the forces which put and keep the 

 GuK Stream in motion, theorists may place them exclusively on one 

 side of the ocean with as much philosophical propriety as on the 

 other. Its waters find their way into the K'orth Sea and the 

 Arctic Ocean by virtue of their specific gi'avity, while water thence, 

 to take their place, is, by virtue of its specific gravity and by counter 

 cmTents, carried back into the Gulf. The dynamical force which 

 causes the Gulf Stream may therefore be said to reside both in the 

 polar and in the intertropical waters of the Atlantic. 



109. As to the temperatm-e of the Gulf Stream, there is, in a 

 Winter temperature wiutcr's day, off Hattcras, and even as high up as 

 oftheGuifsueam. ^j^g Grand Banks of Ne\N^oimdland in mid-ocean, a 

 difference between its waters and those of the ocean near by of 20° 

 and even 30°. Water, we know, expands by heat, and here the 

 difference of temperatm-e may more than compensate for the differ- 

 ence in saltness, and leave, therefore, the waters of the Gulf Stream, 

 though Salter, yet lighter by reason of their warmth. 



110. If they be Hghter, they should therefore occupy a higher 

 Top of Gulf stream Isvcl than thoso through which they fiow. Assum- 

 roof-sbaped. ^j^g j-^^q depth off Hattcras to be one hundred and 

 fom'teen fathoms, and allowing the usual rates of expansion for sea 



the water in this basin be more or less salt than that of the intertropical seas, we 

 know it is quite different in temperature, and difference of temperature will beget 

 currents quite as readily as difference in saltness, for change in specific gravity 

 follows either. 



