180 THE OCEAN. [Book VIIT. 



the currents of the ocean. . . . Operating incessantly 

 on the surface of the ocean,' the wind 'causes, in the 

 first instance, a gentle, but general, motion of the 

 fluid to leeward (as is proved by ships being always 

 found to leeward of their reckonings in the Trade 

 Winds) ; and the water so put in motion forms, by 

 accumulation, streams of current.' ■*• 



Here, without argument, the author quoted 

 assumes the very basis of the question at issue to 

 be proved. For, though the motion of the ships to 

 leeward when sailing in the Trade Winds be accepted 

 as a proof that the water in which they sail moves to 

 leeward, it is clearly no proof that the motion of the 

 water is caused by the winds : but as far as this 

 motion to leeward is concerned, the atmospheric and 

 the oceanic currents may both be effects resulting 

 from the action of the same cause, vis-inertice ; the 

 pressure of the superincumbent atmosphere, in more 

 rapid motion than the water, tending only, to some 

 extent, to increase the natural motion of the latter 

 in those localities where, as is generally the case in 

 the region of the Trade Winds, the action of vis- 

 inertise is westwards in both fluids. If all the 

 oceanic motion westwards under the Trade Winds 

 be proved to be caused by those winds, as Major 

 Rennell assumes it to be, we then certainly have 

 force sufiicient to account for the ocean currents 

 which exist, without seeking for other causes ; but 



' In the work mentioned on p. 129. 



