il6 THE OCEAN. [Book IV. 



before described, so also that which the gravitation 

 of the sun or moon tends to place in any given 

 part of the ocean is carried through the same course 

 in relation to the surface of the earth. The fact 

 of the moon's gravitation drawing the tide eastwards 

 from below the moon, and the sun's gravitation 

 drawing the solar tide westwards from below the 

 sun, has nothing to do with the course of the tide 

 through the ocean after it has been raised by either 

 of those forces. After it is placed in any part of the 

 ocean it is carried from that part, through the course 

 of circulation which vis-inertise determines, without 

 reference to whence it came, just as water placed 

 in any part of the ocean by the earth's gravitation 

 is carried through the same course of circulation 

 without reference to whence it originally came. 



Whatever the positions of the sun or moon in 

 relation to any given meridian may be, their gravi- 

 tation forms a part of the current- creating force of 

 vis-inertise, acting westwards on that meridian just 

 as much as on any other meridian. The tidal action 

 of the sun and moon is, therefore quite distinct from 

 the current- creating action of vis-mertiaa, though the 

 gravitation of the sun and moon is merged in, and 

 forms a part of, this current-creating force of vis- 

 inertiae. 



The tides, as they are broken by the coast- 

 lines, are constantly being thrown into the course of 

 the ocean currents resulting from the action of vis- 



