TIDES. 



35 



clear that the Mediterranean would long ere this have been a vat of 

 strong brine, or a bed of cubic crystals." 



For the same reason, Dr. Maury considers it certain that there is 

 an under current to the south of Cape Horn, which carries into the 

 Pacific Ocean the overflowings of the Atlantic. In fact, the Atlantic 

 is fed unceasingly by the Great American rivers, while the Pacific 

 receives 'no important affluent, but ought to be, and is, subjected to 

 enormous losses, in consequence of the evaporation continually taking 

 place at the surface. 



TIDES. 



Tides are periodical movements produced by the attraction of the 

 sun and moon. This action, which influences the whole mass of the 

 earth, is made manifest by the swelling movement of the waters. 

 The attractive force exercised by the moon is three times that of the 

 sun, in consequence of its approximation to the earth, as compared to 

 the greater luminary. 



In order to comprehend the theory of tides, we shall first consider 

 the lunar influences, putting aside for a moment the solar action. 



South Pole. 



Fig. 5. Lunar Tides. 



The attraction which the moon exercises upon any point on the 

 earth's surface is in the inverse ratio of the square of its distance. 



D 2 



