146 DISCUSSIONS IN CLIMATOLOGY. 



80°, it is then 120° less than it would be did the tem- 

 perature of each place depend alone on the heat 

 received directly from the sun. This great reduction 

 from about 200° to 80° can, of course, be due to no 

 other cause than to a transference of heat from the 

 equator to the poles. The question then arose, by 

 what means was this transference effected? There 

 were only two agencies available — the transference 

 must be effected either by aerial or by ocean-currents. 

 It was shown at considerable length (' Climate and 

 Time,' pp. 2.7-30, and other places) that the amount of 

 heat that can be conveyed from the equator to the 

 poles by means of aerial currents is trifling, and that, 

 consequently, the transference must be referred to the 

 currents of the ocean. It became obvious then that 

 the influence of ocean-currents in the distribution of 

 heat over the globe had been enormously under- 

 estimated. In order to ascertain with greater 

 certainty that such had been the case, I resolved 

 on determining, if possible, in absolute measure, the 

 amount of heat actually being conveyed from the 

 equator to temperate and polar regions by means of 

 ocean-currents. 



The only great current whose volume and tempera- 

 ture had been ascertained with any degree of certainty 

 is the Gulf Stream. On computing the absolute 

 amount of heat conveyed by that stream, it was found 

 to be more than equal to all the heat received from 

 the sun within 32 miles on each side of the equator. 

 The amount of equatorial heat carried into temperate 

 and polar regions by this stream alone is therefore 

 equal to one-fourth of all the heat received from 

 the sun by the North Atlantic from the Tropic of 

 Cancer up to the Arctic circle .* Although the heating - 



* 'Climate and Time,' pp. 34, 35; "Phil. Mag.," February, 1870. 



