58 THE OCEAN. [Book TII. 



comparatively infinitesimal in comparison witli tlie 

 greater force proceeding from otter centres of attrac- 

 tion ; it must nevertheless, of necessity, be a power 

 acting throughout the universe, modifying more or 

 less the effects of other forces of gravitation. 



If this be not so, then the law of gravitation 

 above mentioned is not true ; for that law is an effect 

 necessarily resulting from this as a cause. They are 

 inseparable as cause and effect. It is the fact of 

 gravitation being of the nature described which 

 necessitates that the force of attraction proceeding 

 from any power of gravitation must be inversely as 

 the square of the distance from which it acts. And 

 since this law could no more exist without gravita- 

 tion being of the nature above described than gravi- 

 tation could be of that nature without causing this 

 law, it must be admitted that any given particles 

 of the ocean are acted upon by forces of attraction 

 proceeding from every power of gravitation in the 

 universe. 



Let us suppose those particles to be at any given 

 time or place in the position in which the joint action 

 of all powers of gravitation tends to hold them. 



The particles in question are held by the earth's 

 gravitation, as well as by universal gravitation ; and 

 therefore, when the earth moves it tends to draw 

 those particles with it : but, since those particles are 

 in the position in which universal gravitation tends 

 to hold them, the action of the earth is, therefore, 



