§ 109. THE GULF STREAM. g- 



The dynamical force Stream may witli as much propriety be said to re- 

 £uf sfream\Vbe sidc in thoso northern waters as in the West In- 

 en"cfa?tc?'spedfij ^lia scas ; for on one side we have the Caribbean 

 a^Sd'plTwJ: Sea and Gulf of Mexico, with their waters of brine; 

 *^"- on the other, the great Polar basin, the Baltic, and 



the North Sea, the two latter with waters that are but little more 

 than brackish."^ In one set of these sea-basins the water is heavy ; 

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

 water is bound to seek and to maintain its level ; and here, there- 

 fore, we unmask one of the agents concerned in causing the Gulf 

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

 other agents, and how much ? We can not sa}^ ; 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 vapor, into the Caribbean 

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

 to conclude that the salt which the trade-wind vapor 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 run- 

 ning 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 Gulf 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 

 North Sea and the Arctic Ocean by virtue of their specific grav- 

 ity, while water thence, to take their place, is, by virtue of its spe- 

 cific gravity and by counter currents, 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 temperature of the Gulf Stream, there is, in a 



* The Polar basin has a-known water area of 3,000,000 square miles, and an un- 

 explored area, including land and water, of 1,500,000 square miles. Whether 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. 



