PHYSICAL GEOGRAPHY. 307 



iwecn the tropics (termed the equatorial or rotation current) 

 is considered to be owing to the propagation of tides and to 

 the trade winds. Its direction is changed by the resistance 

 it experiences from the prominent eastern shores of continents. 

 The results recently obtained by Daussy regarding the veloo 

 ity of this current, estimated from observations made on the 

 distances traversed by bottles that had purposely been thrown 

 into the sea, agree within one eighteenth with the velocity of 

 motion (10 French nautical miles, 952 toises each, in 24 hours) 

 which I had found from a comparison with earlier experi- 

 ments.* Christopher Columbus, during his third voyage, 

 when, he was seeking to enter the tropics in the meridian of 

 TenerifFe, wrote in his journal as follows :f " I regard it as 

 proved that the waters of the sea move from east to west, as 

 do the heavens (las aguas van con los cielos), that is to say, 

 like the apparent motion of the sun, moon, and stars." 



The narrow currents, or true oceanic rivers which traverse 

 the sea, bring warm water into higher and cold water into 

 lower latitudes. To the first class belongs the celebrated 

 Gulf Stream, $ which was known to Anghiera, and more 

 especially to Sir Humphrey Gilbert in the sixteenth century. 

 Its first impulse and origin is to be sought to the south of 

 the Cape of Good Hope ; after a long circuit it pours itself 

 from the Caribbean Sea and the Mexican Gulf through the 

 Straits of the Bahamas, and, following a course from south- 

 sou iii west to north-northeast, continues to recede from the 

 shores of the United States, until, further deflected to the 

 eastward by the Banks of Newfoundland, it approaches the 

 European coasts, frequently throwing a quantity of tropical 

 seeds (Mimosa scandcns, Guilandina bonduc, Dolichos urens) 

 on the shores of Ireland, the Hebrides, and Norway. The 

 northeastern prolongation tends to mitigate the cold of the 

 ocean, and to ameliorate the climate on the most northern ex- 

 tremity of Scandinavia. At the point where the Gulf Stream 



* Humboldt, Relat. Hist., t. i,, p. G4 ; Noitvellcs Annales dcs Voyages 

 1839, p. 255. 



t Humboldt, Examen Crit. de FHist. de la Giogr., t. iii., p. 100. 

 Columbus adds shortly after (Navarrete, Coleccion de los Viagcs y De- 

 tcubrimientos de los Espanoles, t. i., p. 260), that the movement is 

 strongest in the Caribbean Sea. In fact, Rennell terms this region, 

 " not a current, but a sea in motion" (Investigation of Currents, p. 23). 



\ Humboldt, Examen Critique, t. ii., p. 250 ; Relat. Hist., t. i., p. 

 66-74. 



$ Petrus Martyr de Anghiera, De Rebus Oceanicis et Orbe Novo 

 Bas., 1523, Dec. iii., lib. vi., p. 57. See Humboldt, Examen Critique 

 t U., p. 251-257, am/ t. iii., p. 108. 



