308 COSMOS. 



is deflected from the Banks of Newfoundland towaid tht east^ 

 it sends off branches to the south near the Azores.* This is 

 the situation of the Sargasso Sea, or that great bank of weeds 

 which so vividly occupied the imagination of Christopher Co- 

 lumbus, and which Oviedo calls the sea-weed meadows [Pra- 

 cierias de yerva). A host of small marine animals mhabits 

 these gently-moved and evergreen masses of Fucus natans 

 one of the most generally distributed of the social plants of 

 ihe sea. 



The counterpart of this current (which in the Atlantic 

 Ocean, betv/een Africa, America, and Europe, belongs almost 

 exclusively to the northern hemisphere) is to be found in the 

 South Pacific, where a current prevails, the effect of whose low 

 temperature on the climate of the adjacent shores I had an 

 opportunity of observing in the autumn of 1S02, It brings 

 the cold waters of the high southern latitudes to the coast of 

 Chili, follows the shores of this continent and of Peru, first from 

 south to north, and is then deflected from the Bay of Arica on- 

 ward from south-southeast to north-northwest. At certain 

 seasons of the year the temperature of this cold oceanic cur- 

 rent is, in the tropics, only 60*^, while the undisturbed adjacent 

 water exhibits a temperature of 81^"5 and 83^-7. On that 

 part of the shore of South America south of Payta, which in- 

 clines furthest westward, the current is suddenly deflected in 

 the same direction from the shore, turning so sharply to the 

 west that a ship sailing northward passes suddenly from cold 

 into warm watei. 



It io not known to what depth cold and warm oceanic cur- 

 rents propagate their motion ; but the deflection experienced 

 by the South African current, from the LaguUas Bank, which 

 is fully from 70 to 80 fathoms deep, would seem to imply the 

 existence of a far-extending propagation. Sand banks and 

 shoals lying beyond the line of these currents may, as was first 

 discovered by the admirable Benjamin Franklin, be recognized 

 by the coldness of the water over them. This depression of 

 the temperature appears to me to depend upon the fact that, 

 by the propagation of the motion of the sea, deep waters rise 

 to the margin of the banks and mix with the upper strata. 

 My lamented friend. Sir Humphrey Davy, ascribed this phe- 

 nomenon (the knowledge of which is often of great practical 

 utility in securing the safety of the navigator) to the desce^^t 

 of the particles of water that had been cooled by nocturnal va. 



* IlumljolJt, E-vaimn Crit., t. ij'., p. G-i-109 



