SECT. XIII. CURRENTS IN THE OCEAN. 95 



are perpetually describing between the parallels of eleven 

 and forty- three degrees of latitude, may be accomplished 

 by any one particle in two years and ten months. In 

 the center of this ^current is situated the wide field of 

 floating sea-weed called the grassy sea. Besides this 

 there are branches of the Gulf-stream, which convey 

 the fruits, seeds, and a portion of the warmth of the 

 tropical climates to our northern shores. 



The general westward motion of the South Sea, togeth- 

 er with the south polar current, produce various water- 

 courses in the Pacific and Indian Oceans, according as 

 the one or the other prevails. The western set of the 

 Pacific causes currents to pass on each side of Australia, 

 while the polar stream rushes along the bay of Bengal : 

 the westerly current again becomes most powerful to- 

 ward Ceylon and the Maldives, whence it stretches by 

 the extremity of the Indian peninsula past Madagascar, 

 to the most southern point of the continent of Africa, 

 where it mingles with the general motion of the seas. 

 Icebergs are sometimes drifted as far as the Azores 

 from the north pole, and from the south pole they have 

 come even to the Cape of Good Hope. But the ice 

 which encircles the south pole extends to lower latitudes 

 by 10 than that which surrounds the north. In conse- 

 quence of the polar current Sir Edward Parry was 

 obliged to give up his attempt to reach the north pole 

 in the year 1827, because the fields of ice were drifting 

 to the south faster than his party could travel over them 

 to the north. 



As distinct currents of air traverse the atmosphere in 

 horizontal strata, so in all probability under currents in 

 the ocean flow in opposite directions from those on the 

 surface ; and there is every reason to believe that the 

 cold waters, deep below the surface of the sea in the 

 equinoctial regions, are brought by submarine currents 

 from the poles, though it is not easy to prove their ex- 

 istence. 



