18 THE OCEAN. [Book II. 



equator and tlie poles, it is obvious that tlie force of 

 \Yestward pressure imparted to any given mass of 

 water lying about the equator is greater than that 

 imparted to an equal mass of water lying about the 

 poles. 



And also, since the velocity of rotation at the 

 surface of the ocean is greater than at the bottom ; 

 therefore in all parts of the ocean the westward 

 pressure imparted to the water at the surface is 

 greater than that imparted to the water lying be- 

 neath it. 



In order to illustrate the action of these unequal 

 forces when brought into conflict, let it be observed 

 that : if an ordinary globe be held by its stand a.nd 

 be, with a rapid motion, moved in a curve line in a 

 plane at right angles to the axis of its poles, as 

 from D to E in Plate III., then, if the onward motion 

 be suddenly arrested, the globe will rotate on its 

 axis ; the axial rotation being in the direction ahbl. 



This motion of rotation results from the in- 

 equality of the forces of onward impetus generated 

 on the sides A and b by the movement of the globe 

 in a curve line from d to e. 



For the curve line a a is similar to, but greater 

 than, the curve line b b : and, as the point A describes 

 the curve line A A in the same time that the point b 

 describes the curvfe line b b, therefore the velocity of 

 the point a is greater than that of the point b ; and, 

 on the onward motion of the axis being arrested, the 



