182 THE OCEAN. [Book VHI. 



of the Atlantic operate upon the currents between 

 25° N. and the equator, log-books containing no less 

 than 380,284 observations on the force and direction 

 of the wind in that ocean were examined. The data 

 thus afforded were carefully compared and discussed. 

 The results show that within those latitudes, and on 

 the average, the wind from the NE. quadrant is in 

 excess of the winds from the SW. only 111 days 

 out of the 365. During the rest of the year the SW. 

 counteract the effect of the NE. winds upon the 

 currents. Now can the NE. trades, by blowing for 

 less than one-third of the time, cause the Gulf 

 Stream to run all the time, and without varying its 

 velocity, either to their force or their prevalence ? ' ^ 



For these and many other reasons of the same 

 nature, given at length in his work on the Physical 

 Geography of the Sea, Captain Maury rejects the 

 theory which makes the wind the prime mover of the 

 oceanic currents, and considers that — ' If we except 

 the tides, and the partial currents of the sea, such as 

 those that may be created by the wind, we may lay 

 it down as a rule that all the currents of the ocean 

 owe their origin to difference of specific gravity 

 between sea- water at one place and sea- water at 

 another ; for wherever there is such a difference, 



^ Physical Geography of the Sea, by M. F. Maury, LL.D. 

 U.S.N. (New York, 1861), sec. 78. See also the extract from 

 Rennell given on page 129 of this volume, regarding the current 

 alluded to as assisting vessels in their pi'Ogress northwai'ds against 

 the North-East Trade Wind. 



