6 THE OCEAN. [Book I. 



ocean. Opinion has always been divided on the sub- 

 ject ; and some investigators, considering that neither 

 of the foregoing causes satisfactorily explains the 

 observed circulation of the ocean, have attributed the 

 ocean currents to the axial rotation of the earth, or 

 have endeavoured to connect them with the tidal 

 action of the sun and moon. 



All the foregoing views appear to have forced 

 themselves upon the consideration of practical inves- 

 tigators. But since the days of Newton, the gene- 

 rality of men most abstrusely acquainted with what 

 are regarded as the higher branches of scientific 

 knowledge, have absolutely rejected the tides and the 

 earth's rotation from among the possible causes of 

 ocean currents, considering their current- creating 

 action incompatible with the accepted laws of motion. 



The laws on which their philosophy is based thus 

 compel those who understand and accept those ' laws 

 of motion ' to conclude that either the winds, or 

 unequal specific gravity resulting from difi'erence of 

 temperature or otherwise, or those two causes com- 

 bined, must necessarily in some manner explain the 

 circulation of the ocean. 



It is, however, evident that whatever may be the 

 current-creating action of the forces above alluded 

 to, the fact of the tides being clearly dependent on 

 the apparent motions of the sun and moon, shows 

 that a full solution of the movements of the ocean 

 cannot be attained through the consideration of merely 



