94 DISCUSSIONS IN CLIMATOLOGY. 



condition. Nothing could be further from the truth 

 than such a supposition. I can boldly affirm that 

 the necessity for geographical conditions is as truly a 

 part of my theory as of Mr. Wallace's modification 

 thereof. 



One of the most important agencies, according to 

 my view, is the enormous amount of heat conveyed 

 from equatorial to temperate and polar regions by 

 means of ocean-currents, and the deflection of this 

 heat, during a high state of eccentricity, from the one 

 hemisphere to the other. But all this depends on 

 ocean-currents flowing from equatorial to polar regions ; 

 and the existence of these currents in turn depends, to 

 a large extent, on the contour of the continents and 

 the particular distribution of sea and land. Take, as 

 one example, the Gulf -stream, a current which played 

 so important a part in the phenomena of the glacial 

 epoch. A very slight change in geographical con- 

 ditions, such as the opening of communication between 

 the Gulf of Mexico and the Pacific, would have greatly 

 diminished, if not entirely destroyed, that stream. 

 Or, as I showed on a former occasion, a change in the 

 form or contour of the north-east corner of the South- 

 American continent would have deflected the great 

 equatorial current, the feeder of the Gulf-stream, into 

 the Southern Ocean and away from the Carribean 

 Sea. One of the main causes of the extreme condition 

 of things in North-western Europe, as well as in 

 eastern parts of America, during the glacial epoch, 

 was a large withdrawal of the warm waters of the 

 Gulf-stream ; and this was to a great extent due, as I 

 stated in my very first paper on the subject * to the 

 position of Cape St. Roque, which deflected the 

 equatorial current into the Southern Ocean. That a 



* "Phil. Mag," for August, 1864. 



