184 The Realm of Nature CHAP. 



of a watch in the northern Atlantic, and as if stirred in the 

 opposite direction in the southern part of the ocean. The 

 centre of each whirl is nearly at rest, and immense quan- 

 tities of floating sea-weed accumulate, especially in the North 

 Atlantic, where the calm weed-hampered water is known as 

 the Sargasso Sea. Mr. A. W. Clayden has devised an 

 interesting model, in which a current of air sets up real 

 currents on a water surface formed like the Atlantic. So 

 far as can be gathered from the imperfect data more water 

 is driven poleward by this circulation than returns in surface 

 currents. Much of the surface water sinks off the British 

 Islands ( 244) south of the Wyville- Thomson Ridge 

 (258). Over this ridge the Atlantic water streams so 

 strongly that the bottom is swept clear of mud to the depth 

 of 500 fathoms. North of the Ridge the basin of the 

 Norwegian Sea is filled up to its lip with ice-cold water from 

 the Arctic region which finds no exit southward. 



247. Currents of the Pacific Ocean. The Pacific 

 Ocean, on account of its vast extent and its remoteness 

 from great trade routes until within recent years, has not 

 been so carefully studied as the Atlantic. It is known, 

 however, that the general system of its circulation is the 

 same, and the map should be carefully studied in order to 

 recognise the similarities. The Bight of Panama, extend- 

 ing along the west coasts of Central America and of 

 the north of South America, serves, like the Gulf of 

 Guinea, as the starting-place of the great equatorial current 

 system. The south-east trade wind produces the Peru 

 Current as a stream of cool water raised by the off-shore 

 winds, precisely like the Benguela Current of the Atlantic. 

 This stream, deflected westward by the Peruvian outcurve 

 of the coast, sweeps as a South Equatorial Current past 

 the Galapagos Islands on the equator, giving them a cooler 

 climate than any other equatorial land. Setting westward 

 before the steady trade winds, it sends off branches to the 

 south, which wind amongst innumerable island groups, and 

 ultimately reunite under the influence of the brave west 

 winds, and drift eastward to rejoin the Peru Current. The 

 main branch of the South Equatorial Current splits at New 



