170 THE OCEAN. • [Book VII. 



the given position, gravitation draws other particles 

 into the position vacated. 



According to the foregoing considerations — first, 

 as regards the orbital motion of the earth, or any- 

 onward motion of the earth : — as the earth moves in 

 any given direction, then, wherever least obstruc- 

 tion exists to prevent the progress of the water in 

 the opposite direction, there vis-inertise acts more 

 freely than elsewhere : its existence as a cause neces- 

 sitates an effect, and, as any particles are set in 

 motion by vis-inertise, gravitation draws other par- 

 ticles into the positions vacated, to be in their turn 

 expelled and replaced — and so on, as long as the 

 motion which causes the preponderating action of vis- 

 inertise to occupy any given position lasts. And thus 

 a circulation of the ocean is effected by a current run- 

 ning through the deep and central parts of the ocean 

 in the opposite direction to that of the earth's onward 

 motion, and returning to the source of action by 

 counter- currents along the shores ; and this without 

 the position of the ocean, as a whole, being in any 

 way affected, as it is carried along with the motion of 

 the earth, firmly held to the earth's surface by the laws 

 of gravitation. 



Then also, as regards the axial rotation of the earth 

 eastwards — in which, as already explained, there is not 

 only the current-creating action westwards through 

 the deep and central parts of the ocean, but also that 

 great inequality in the velocity of the motion in polar 



