Chap. II.] INERTION. 41 



and bottom of the ocean, this is a question to be con- 

 sidered in the practical investigation of the move- 

 ments of the ocean. 



PAET IV. 



EPPECTS IN THE OCEAN AS IT IS. 



In the actual configuration of land and water on 

 the surface of the earth, there are, as far as westward 

 pressure is concerned, two great force- creating re- 

 gions in the ocean — one the equatorial region of the 

 Atlantic, the other that of the Pacific and Indian 

 Oceans. The Pacific and Indian Oceans, being con- 

 nected in the force- creating regions, must be re- 

 garded as subdivisions of the same district : and, as 

 pointed out in the preceding part of this chapter, 

 barriers of islands, or ridges over which the water is 

 comparatively shallow, form other subdivisions, theo- 

 rectically similar, though not so distinctly marked as 

 that which forms the Indian Ocean. 



In the northern hemisphere, the comparatively 

 unimportant opening of Behring's Strait being the 

 only communication between the Pacific and Atlantic 

 Oceans, we have two oceans which, as shown in the 

 chart on Plate II., should each contain an equatorial 

 and a polar district of currents analogous to those 

 whose formation has been described in Part III. of 

 this chapter, and illustrated in Plate YI. 



