92 THE OCEAN. [Book UI. 



For the revolving force increases towards the centre, 

 and as any particle is carried onwards by it, the par- 

 ticle next outside it is carried relatively in exactly 

 the opposite direction by the force of astral gravita- 

 tion, the action of which is relatively greater, as re- 

 gards the revolving force, on it than on the particle 

 nearer the centre of rotation. Its motion backwards 

 along the tangent results from the effort of vis- 

 inertias to maintain the equilibrium destroyed by the 

 particles nearer the centre of rotation being carried 

 in the opposite direction. 



The above argument is equally applicable to the 

 moon ; for, suppose the latter to be lying loosely on 

 the surface of the earth, and let a motion of rotation 

 be generated in the earth, and then, as that motion 

 carries the surface on which the moon rests onwards, 

 astral gravitation, whose action, compared with the 

 revolving force, is relatively greater on the moon 

 than on the surface below it, maintains the equili- 

 brium of gravitation by carrying the moon in the 

 opposite direction, which is backwards along the tan 

 gent to the surface on which it rested. And it will 

 continue to recede along that tangent as long as the 

 disturbed equilibrium is more readily restored by 

 that motion than by the motion of the opposite side 

 of the rotating surface, or of some other body in the 

 same direction. At the distance thus determined it 

 would revolve with the rotating surface, though con- 

 stantly lagging backwards over it under the action 



