OCEANIC CIRCULATION. 235 



average the wind from the north-east is in excess of 

 the wind from the south-west only 111 days -out of the 

 365. Now, can the north-east 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 prevalence.' Our reviewer 

 not only dwells on the wrongheadedness of this argu- 

 ment wholly irresistible as it appears but asserts 

 that ' the trade-wind origin of the Gulf Stream is about 

 as certain as the rotundity of the earth.' It could have 

 been wished that in place of abusing Captain Maury for 

 wrongheadedness, the reviewer would have devoted a 

 few lines to the demolition of Maury's argument. 



Maury himself advanced the relative lightness of the 

 equatorial water as the true reason of the oceanic circu- 

 lation. But granting that the expansion of the equa- 

 torial water under the sun's heat, as well as the resulting 

 buoyancy, would cause an overflow of equatorial water 

 polewards, this overflow would be an exceedingly slow 

 movement, and it would result in an eastwardly instead 

 of a westwardly flow, for the very same reason that the 

 counter trade- winds travelling polewards assume an 

 eastwardly direction. 



In the Student for July 1868, I advanced another 

 explanation. I urged that the sun's action on the 

 equatorial and tropical regions of the Atlantic, raising 

 immense quantities of water by evaporation, causes an 

 influx of water from below. ' There can be no question,' 

 I then wrote, ' that under-currents arriving in this 

 manner, whether from the north or from the south' 



