CO THE OCEAN. [Book III. 



parts of the ocean are caused by the action of the 

 foreign force of gravitation, just as the counter- 

 currents are caused by the earth's gravitation. The 

 ocean, as a whole, must maintain its position in re- 

 lation to the conflicting forces. And if, on the one 

 hand, it may be said that the vis-inertise of the 

 ocean, opposing the earth's tendency to carry it from 

 its position, causes a current in one direction, and 

 that the earth's gravitation draws counter- currents 

 in the opposite direction ; so also may it, with equal 

 propriety, be said that the vis-inertige of the ocean 

 opposes the action of the foreign force of gravitation, 

 and, as the attraction of the latter tends to draw it 

 from its position, and draws a current through those 

 parts of the ocean most free to follow its attraction, 

 the vis-inertia of the ocean maintains its position 

 as a whole by means of counter-currents through 

 those parts of the ocean which are least free to fol- 

 low the attraction of the foreign force of gravitation. 

 That which is the vis -inertia current, in relation to 

 the earth's gravitation, is the attraction current in 

 relation to the foreign force of gravitation ; and those 

 which are attraction currents in relation to the earth's 

 gravitation are vis-inertice currents in relation to the 

 foreign force of gravitation. 



Thus the vis-inertise which draws the currents 

 westwards in the equatorial regions is, in fact, at- 

 traction proceedmg from the joint action of all foreign 

 powers of gravitation ; and the earth's power of 



