Ch. XX.] 



CAUSES OF CUEEENTS. 



49!) 



a 





ii- 



M 



called Cape St. Eoque, it divides itself into two parts one 

 portion of which pursues a southerly course along the coast 

 of Brazil, while the principal part of it flows westward and 

 skirting the coast of Guiana, is reinforced by the waters of 

 the Amazons and Orinoco, which impart to it an accelerated 

 speed. After passing the island of Trinidad, it expands and 

 contributes in some degree to raise the waters of the Carri- 

 bean Sea and Gulf of Mexico, which are also supposed to 

 be heaped up by the blowing of the north-east trade winds a 



coin Duration 01 circumstances wnicn gives rise to the Gulf- 

 stream. 



The last-mentioned current has already been alluded to in 

 the twelfth chapter, p. 244, as moderating the cold ofalaro-e 

 part of the northern hemisphere. A curious fact is related 

 by General Sabine as illustrating the combined effects of the 

 equatorial and Gulf currents last alluded to. He happened 

 to visit the African coast in 1822, when a vessel was wrecked 

 at Cape Lopez, near the equator, and the year after he was 

 at Hammerfest, in Norway, near the North Cape of Europe, 

 when casks of palm oil derived from the same wrecked 

 vessel were thrown on shore. They had crossed the Atlan- 

 tic south of the line in a direction from east to west, made 

 the circuit of the West Indian Islands, and then re-crossed 

 the Atlantic north of the line from west to east. The last, 

 or northern part of their course, may possibly, says General 

 Sabine, have been due not wholly to the original impulse of 

 the Gulf-stream, but to the west and south-west winds which 

 prevail to the northward of the trades. 



From the above statements we may understand why 

 Rennell has characterised some of the principal currents as 

 oceanic rivers, which he describes as being from 50 to 250 



miles in breadth, and having a rapidity exceeding that of the 

 largest navigable rivers of the continents, and so deep as to 

 be sometimes obstructed, and occasionally turned aside, by 

 banks, the tops of which do not rise within forty, fifty, or 

 even one hundred fathoms of the surface of the sea.* 



)/ currents.— The ordinary velocity of the 

 of the ocean is from one to three miles 



Rennell on Currents, p. 58. 



K K 2 



