the Distribution of Heat over the Globe. 87 



nave doubled the actual volume of the stream ; 2nd, that I have 

 not taken into account the great length of time that the water 

 requires in order to circulate, and the interference that it has to 

 encounter in its passage. Although I feel satisfied that the 

 actual quantity of water conveyed from the Gulf of Mexico is as 

 great, if not greater than what I have estimated it to be, yet the 

 influence of the stream on climate, as we shall presently see, is 

 so enormous, that for our present purposes it matters little 

 whether we adopt Mr. Findlay's estimate or mine as the correct 

 one. 



In this case I shall adopt Mr. Findlay's estimate, and take the 

 volume of the stream at one-half what I have concluded it to 

 be. The quantity of heat conveyed would still be equal to all 

 the heat received from the sun within 31 \ miles on each side 

 of the equator, or equal to nearly one-half of the entire heat 

 received by the arctic regions. 



I may here briefly consider the second objection, as it will 

 afford an opportunity of referring to some important conside- 

 rations bearing on the mode by which the heat of ocean-currents 

 is distributed over the land. 



The objection is, that a stream so comparatively small as the 

 Gulf-stream, after spreading out over such a large area of the 

 Atlantic, and moving so slowly across to the shores of Europe, 

 losing heat all the way, would not be able to produce any very 

 sensible influence on the climate of Europe. 



I am unable to perceive the force of this objection. Why, the 

 very efficiency of the stream as a heating- agent necessarily de- 

 pends upon the slowness of its motion. Did the Gulf-stream 

 move as rapidly along its whole course as it does in the Straits 

 of Florida, it could produce no sensible effect on the climate of 

 Europe. It does not require much consideration to perceive 

 this. (1) If the stream during its course continued narrow, 

 deep, and rapid, it would have little opportunity of losing its 

 heat, and the water would carry back to the tropics the heat 

 which it ought to have given off in the temperate and polar 

 regions. (2) The Gulf-stream does not heat the shores of Europe 

 by direct radiation. Our island, for example, is not heated by 

 radiation from a stream of warm water flowing along its shores. 

 The Gulf- stream heats our island indirectly by heating the winds 

 which blow over it to our shores. 



The anti-trades, or upper return-currents, as we have seen, 

 bring no heat from the tropical regions. After traversing some 

 2000 miles in a region of extreme cold they descend on the 

 Atlantic as a cold current, and there absorb the heat and moisture 

 which they carry to north-eastern Europe. Those aerial cur- 

 rents derive their heat from the Gulf-stream, or if it is preferred, 



