218 THE OCEAN. - [Book IX. 



the ocean and atmosphere and confirms that south- 

 ward motion of the earth in the first instance 

 deduced from the observed course of the ocean 

 currents.^ 



^ A further development of the action of vis-inertise on the 

 surface of the earth is given in The New Frincij^les, as stated in 

 the footnote to Proposition X., Chapter XXI. of this volume. 



