GBEAT CURRENTS OF THE OCEAN. 



3 



carried violently into the Gulf of Mexico, and there, being 

 collected and concentrated, they rush with rapidity through 

 the Bahama Channel." 



In the Penny Cyclopaedia, where the general opinion on the 

 subject is also given, it is said that " Humboldt, ascribing the 

 formation of these currents to the rotation of the earth, 

 calls them ' currents of rotation.' But he does not dis- 

 tinguish between the proper currents and the drift water, 

 which latter produces a slight western current on the surface 

 of the ocean between the tropics. This latter motion is 

 indeed probably caused by the united effects of the rotation 

 and the trade winds, on the wide-expanded surface of the 

 ocean. The small degree of velocity in this current, how- 

 ever, shews that the stronger currents near the equator 

 cannot arise from the same cause. Rennel thinks that the 

 equatorial currents are caused by the accumulation of great 

 masses of drift-water near the equator, by the north-easterly 

 and south-easterly trade winds. But this opinion will be 

 found inadmissible, when it is considered that such accu- 

 mulation could only produce a superficial current ; and 

 these currents are not superficial, but go to a great depth." 

 Again, in the article on this subject in the Encyclopaedia 

 Britannica it is said, that " in the sea, currents are either 

 natural and general, arising from the diurnal rotation of the 

 earth about its axis; or accidental and particular, caused 

 by the waters being driven against promontories, or into 

 gulfs or straits." 



Thus, all these writers concur in representing the rotatory 

 motion of the earth as the great cause of the oceanic currents 

 that are found within the tropical regions. This rotatory 

 motion causing the tropical parts of the land to move east- 

 ward at a high velocity, as it undoubtedly does, it is assumed 

 that the waters of the ocean must be left behind. But for 

 this assumption there does not appear to be any sufiicient 

 reason assigned, nor indeed is any plausible reason given, 



