THE CAUSE OF THE GLACIAL PERIOD. 313 



service in showing what an enormous transfer of heat 

 there is from the southern to the northern Atlantic by 

 means of the Gulf Stream, estimating that the heat con- 

 veyed by the Gulf Stream into the Atlantic Ocean is equal 

 to one fifth of all possessed by the waters of the North At- 

 lantic ; or to the heat received from the sun upon a mill- 

 ion and a half square miles at the equator, or two million 

 square miles in the temperate zone. " The stoppage of 

 the Gulf Stream would deprive the Atlantic of 77,479,- 

 650,000,000,000,000 foot-pounds of energy in the form of 

 heat per day." 



Among the objections which bear against this ingen- 

 ious theory is one which will appear with great force when 

 we come to discuss the date of the Glacial period, when 

 we shall show that even Professor Hitchcock's supposition 

 that the lingering effects of the last great eccentricity of 

 the earth's orbit, continued down to forty thousand years 

 ago, is not sufficient to account for the recentness of the 

 close of the period as shown by abundant geological evi- 

 dence. It is certainly not more than ten or fifteen thou- 

 sand years ago that the ice finally melted off from the Lau- 

 rentian highlands ; while on the Pacific coast the period 

 of glaciation was still more recent. 



From inspection of the accompanying map the main 

 point of Mr. CrolPs reasoning may be understood. It 

 will be seen that the direction of the currents in the cen- 

 tral Atlantic is largely determined by the contour of the 

 northeastern coast of South America. From some cause 

 the southeast trade-winds are stronger than the northeast, 

 and their force is felt in pushing the superficial currents 

 of warm water farther north than Cape St. Koque, the 

 eastern extremity of Brazil. As the direction of the 

 South American coast trends rapidly westward from this 

 point to the Isthmus of Panama, the resultant of the forces 

 is a strong current northwestward into the cul-de-sac of 

 the Gulf of Mexico, from which there is only the one 



