Mr. J. Croll on the Physical Cause of Ocean-currents. 175 



Now it will be seen, by referring to what has been shown on 

 a former occasion (Phil. Mag. for Oct. 1870, p. 257), that the 

 Gulf-stream and general oceanic circulation would, in such a 

 case, remove from the torrid zone 405 parts of the 975 received 

 from the sun ; and this transferred to the Atlantic in temperate 

 regions, would add 367 to the 757 already possessed by it. In 

 this case the Atlantic in temperate regions would possess 1126 

 parts of heat, whereas the intertropical region would possess 

 only 570 parts ; or, in other words, the Atlantic in temperate 

 regions would have twice the amount of heat possessed by it in 

 intertropical regions. But if we assume that one half of this 

 heat goes into the Arctic Ocean, and the other half remains in 

 the temperate regions, the relative quantities of heat possessed 

 by the three zones will be as follows : — 



Atlantic, in Torrid zone . . . . 570 

 „ in Temperate zone . . . 940 

 „ in Frigid zone .... 766 



It is here assumed, however, that none of the heat possessed 

 by the Gulf-stream is derived from the southern hemisphere, 

 which, we know, is not the case. But supposing that as 

 much as one half of the heat possessed by the stream came from 

 the southern hemisphere, and that the other half was obtained 

 from the seas lying between the equator and the tropic of 

 Cancer, the relative proportions of heat possessed by the three 

 zones per given area would be as follows :— 



Atlantic, in Torrid zone .... 671 

 „ in Temperate zone . . . 940 

 „ in Frigid zone .... 766 



This proves incontestably that, supposing there is such a cir- 

 culation as Dr. Carpenter maintains, the quantity of heat con- 

 veyed by means of it into the North Atlantic and Arctic Oceans 

 must be trifling in comparison with that conveyed by the Gulf- 

 stream ; for if it nearly equalled that conveyed by the Gulf- 

 stream, then not only the North Atlantic in temperate regions; 

 but even the Arctic Ocean itself would be much warmer than 

 the intertropical seas. In fact, so far as the distribution of 

 heat over the globe is concerned, it is a matter of indifference 

 whether there really is or is not such a thing as this general 

 oceanic circulation. The enormous amount of heat conveyed 

 by the Gulf-stream alone puts it beyond all doubt that ocean- 

 currents are the great agents employed in distributing over the 

 globe the excess of heat received by the sea in intertropical 

 regions. 



It is therefore, so far as concerns the theory of a General 

 Oceanic Circulation, of the utmost importance that the advo- 



