POLAR CURRENTS. 35 



uial currents the first in importance are two great 

 streams which flow from the polar towards the equa. 

 torial regions, and, on the breaking up of winter, bring 

 the melting icebergs, and drift ice, sometimes bearing 

 along an astonished walrus or polar bear into lower 

 latitude, until gradually dissipated in the warmer 

 water; the zoological freight being deposited in some 

 unexpected place, to lie till disturbed by a future geo- 

 logist. The north polar current brings icebergs to the 

 Azores in lat. 38 40 N.; while the south polar 

 sometimes strands them on the arid African cape, in 

 lat. 34 S. These powerful streams very sensibly in- 

 fluence the climate of the temperate zones. That of 

 Europe would be rendered much more severe did not a 

 contrary surface current bring warmer waters from the 

 south to supply the drain caused by that flowing from 

 the north. 



The primary cause of the great polar streams may 

 be, as is commonly stated, the centrifugal force of 

 the body of the earth, as it performs its daily revo- 

 lution; this force would no doubt tend to raise the 

 waters on the surface in a belt round the equator. 

 This rising might generate a stream from the poles 

 towards the equator, when the world was first set a 

 spinning; but to maintain that stream perennially 

 many other agencies must be in operation. These are 

 chiefly found in the unequal distribution of heat on 

 the surface of the globe and through the mass of the 

 waters, which disturbs the equilibrium of the fluid, and 

 consequently generates and maintains a movement 

 through it. It is well known that water, when at its 



