4 6 



lantic Ocean in the shape of a fan, as previously described. 

 James Croll [see Philosophical Magazine for 1870] has calcu- 

 lated that the quantity of heat conveyed by the Gulf-stream 

 through the Straits of Florida, and thence into the northren 

 half of the North Atlantic basin, is equal to the heat received 

 from the sun by 1,560,935 square miles at the Equator, most 

 of this heat being derived from the southern hemisphere. 



The Anti-trades, or S.W. winds, which prevail in the 

 North Atlantic during the greater part of the year, and pro- 

 bably also the easterly tendency of a current flowing with a 

 certain velocity from the Equator towards the higher latitudes, 

 must be looked upon as causes which favour the accumula- 

 tion of Gulf-stream water in the narrower portion of the North 

 Atlantic basin. It seems impossible to dissociate the great 

 oceanic currents from the permanent and the periodical currents 

 of the atmosphere. A glance at a physical chart reveals the re- 

 markable parallelism which exists between them. Moreover, 

 the action of the winds on water, and the facility with which 

 they originate currents in the direction in which they happen to 

 blow, are matters of daily observation and of considerable im- 

 portance to the practical navigator. It remains with the 

 opponents of this theory, advocated by Benjamin Franklin, 

 Humboldt, Sir John Herschel, and other trustworthy authori- 

 ties, to discover an equally simple and equally efficient cause 

 of oceanic circulation. 



Henceforth oceanic currents must be looked uponas one 

 of the most powerful agents in the distribution of temperature 

 over the surface of the earth, and their influence on climate 

 such, as almost to invert the effects of latitude, creating the 

 conditions of a temperate or even tropical, climate within the 

 Arctic circle, and vice versa, transferring the conditions of an 

 Arctic climate to the vicinity of the tropics. 



