266 S. Neiocomb — CrolVs Climate and Time. 



support of the wind theory is found in the very obvious gene- 

 ral correspondence between the winds and currents of the 

 ocean, a correspondence so striking that it is difficult to see 

 how the strongest presumption of a c 



liliar phenomenon on our Eastern coast. It is well known 

 that the tides are there materially modified by the winds, so 

 that the time of high water may be delayed or accelerated by 

 an entire hour or more, and the" height changed by one or more 

 feet in consequence of a heavy wind. The effect of a wind 

 thus determined must be the same as that of a diff'erence of 

 level equal to that which the wind is found to produce, and 

 this again must be sufficient to produce a very strong surface 

 current. Moreover, a continuous surface current must, in time, 

 extend itself to a great depth through friction. 



In thus sustaining the wind theory, we must not be under- 

 stood to deny the existence of a general law of oceanic circu- 

 lation which' we understand to be due to Dr. Carpenter, and by 

 which an undercurrent of cold water runs from each pole to 

 the equator, to return as a surface current of warm water. 

 That the mass of ice-cold water which forms the depths of the 

 ocean came from the poles, and that to keep it cold, the sup- 

 ply must be constantly though slowly renewed will, we con- 

 ceive, be disputed by no one. And the renewal of the water 

 necessarily implies a surface set from the equator toward the 

 poles. But, when we inquire whether the quantity of water 

 thus interchanged can be so great as to give rise to the ob- 

 served ocean currents, the answer is not quite clear, and the 

 probabilities seem to incline to the negative. At the same 

 time, we may have here an important feature among 

 causes which produce ocean '" • -=^ *i 



vestigating the. subject 

 alculating the effect 



^.. Perhaps it would be unfaii j . 



not attempt to do this, but the impression left on the mind ot 

 the reader is that the " gravitation theory" of oceanic cu'cula- 

 tion is examined rather to refute it than to determme with 

 mathematical precision what part diff'erences of gravity between 

 the polar and equatorial waters do really play in the phenom- 



While we agree with Mr. Croll in the important part he as- 

 signs to oceanic currents in modifying climate, we cannot ac- 

 cept the reasoning by which he attempts to prove that the cor- 

 responding influence of serial currents is entirely insignificant 

 Speaking of the possible amount of heat conveyed by the up- 

 per currents, or anti-trades, from the equatorial to the polar re- 

 gions, he says : 



