GEEAT CUaRENTS OF THE OCEAN. 



13 



in their accounts; and their statements shew not only that 

 wind can produce rapid motion in the water of the ocean over 

 which it passes, but that it produces the motion in a short 

 time, and while passing over only a limited space. It is 

 always soon after the wind changes that the ocean current 

 changes, and many of the currents run with great force in a 

 direction exactly contrary to that which is erroneously sup- 

 posed to be their natural direction consequent on the rotation 

 of the earth. But if within these comparatively limited spaces 

 wind can soon put water in rapid motion, it is sufficiently 

 evident that the same wind acting on the surface of broad 

 oceans, and for a much longer time, is capable of producing 

 proportionately greater effect, and it may tl:erefore be ad- 

 mitted to be able to create the currents that are found in the 

 widest and deepest seas. 



It has thus been found that all the great oceanic currents 

 that have been pointed out are accompanied by winds ; that, 

 although they sometimes move in accordance with the rota- 

 tory theory, they at other times run in opposition to it, but 

 they always run in the direction of the wind, and they change 

 as the wind changes. The evidence against the rotation theory 

 may therefore be said to be strong and complete, and that 

 theory may be considered erroneous. 



As a consequence of the greater rotatory velocity of the 

 surface of the globe within than without the tropics, it has 

 long been believed that within the tropics the surface of the 

 earth, in its rotation, left the atmosphere behind, and thus 

 produced the eastern tropical trade winds. And certainly, 

 from the greater velocity of the air than of the water of the 

 sea when passing from a slower to a quicker rotating latitude, 

 this was not an unreasonable conjecture ; the Hadleyan theory 

 of winds was therefore plausible. But it has been proved that 

 even the air soon acquires the rotatory velocity of the portion 

 of the globe on which it presses, and is then just as ready to 

 obey local influences as if both itself and the surface were 



