CHAPTER VII. 



EXAMINATION OF MR. ALFRED R. WALLACE'S MODIFI- 

 CATION OF THE PHYSICAL THEORY OF SECULAR 

 CHANGES OF CLIMATE. — Continued. 



Physics in relation to Mr. Wallace's Modification of the Theory. — 

 Another Impossible Condition Assumed. — A Geographical 

 Change not Necessary in Order to Remove the Antarctic 

 Ice. — Other Causes than Antarctic Ice affecting the North- 

 ward-flowing Currents. — Climatic Conditions of the Two 

 Hemispheres the reverse Ten Thousand Years ago ; argu- 

 ment from. — Mutual Reactions of the Physical Agents in 

 Relation to the Melting of the Ice. — Another Reason why the 

 Ice does not Melt. 



I. Physics in Relation to Mr. Wallace's Modification 

 of the Theory. 



The grand modification, that during the height of 

 the glacial epoch the snow and ice would not dis- 

 appear when precession brought the winter solstice 

 round to perihelion, I have already given in Mr. 

 Wallace's own words. As the reasons which he 

 assigns for this modification are very briefly stated 

 by him, I may here give them also in his words. 



After describing the state of North-Eastern America 

 and the North Atlantic, to which I have already 

 alluded, he says: — 



" But when such was the state of the North Atlantic (and, 

 however caused, such must have been its state during the 

 height of the glacial epoch), can we suppose that the mere 

 change from the distant sun in winter and near sun in 



