78 THE OCEAX. [Book III. 



earth's gravitation tends to give it ; but tlie moon is 

 already held in equilibrium by universal gravitation, 

 and therefore, as the earth tends to draw it in any 

 direction from that position, astral gravitation, or the 

 combined action of all other forces of gravitation, 

 tends to draw it in the opposite direction.^ 



^ See The New Princiiyles of Natural PJiilosophy, Chapter III. 



