28 THE OCEAN. [Book II. 



Thus there 'would be formed two great zones of 

 currents in each hemisphere, as shown on Plate Y., 

 in which figure 1 represents the currents of the upper 

 strata, and figure 2 those of the under strata.^ 



The under strata in the equatorial zone run 

 towards the equator at all points from north-east 

 and south-east ; and in each polar zone run towards 

 the pole from south-west in the northern, and from 

 north-west in the southern hemisphere. 



And in the upper strata, the great westward 

 current of the equatorial zone diverges from the 

 equator on both sides ; the diverging streams tendmg 

 in their course more and more directly towards the 

 poles, and then eastwards, until meeting with the 

 streams running from north-east in the north polar 

 zone and from south-east in the south polar zone. 



PAET III. 



EFFECTS IN AN OCEAN SUEEOUNDED BY LAND. 



Section I. — Equatorial and Polar Districts. 



The course of the currents just described is that 



which would result from the action of westward 



pressure if acting in an ocean covering the surface 



of the earth and unobstructed anywhere by land. 



^ This circulation is demonstrated by a shorter mathematical 

 argument in Chapter III. of The New Principles of Natural 

 Philosophy, which does not, however, so well serve as a basis 

 for the subsequent details. See also, farther on in this volume, 

 Chapter XXI., Proposition XXVII. 



