298 MODES OF ACCOUNTING FOR 



evaporation in the equatorial regions and consequently a 

 greater supply of the raw material of snow in the temperate 

 regions during the winter months. 



Thirdly. The effect of an altered position of land and water. 



This cause, which has been advocated by Sir C. Lyell 

 might, indeed, have the effect attributed to it ; but it seems 

 scarcely applicable to the present difficulty, because the 

 geography of Western Europe must have been nearly the 

 same during the period under consideration, as it is at 

 present. 



Fourthly. An alteration in the earth's axis. 



The possibility of such a change has been denied by 

 many astronomers. Sir J. W. Lubbock, on the contrary, has 

 maintained* that it would necessarily follow from upheavals 

 and depressions of the earth's surface, if only they were of 

 sufficient magnitude. The same view has recently been taken 

 by other mathematicians. This suggestion, however, like 

 the preceding, involves immense geographical changes, and 

 would therefore necessarily have required an enormous lapse 

 of time. 



Fifthly. Mr. Hopkins inclines to find another solution of 

 the difficulty in the supposition that the Gulf Stream did 

 not. at this period warm the shores of Europe. "A de- 

 pression of 2000 feet would/' he says, " convert the Missis- 

 sippi into a great arm of the sea, of which the present Gulf 

 of Mexico would form the southern extremity, and which 

 would communicate at its northern extremity with the 

 waters occupying the .... great valley now occupied by 

 the chain of lakes." In this case the Gulf Stream would no 

 longer be deflected by the American coasts, but would pass 

 directly up this channel into the Arctic Sea ; and as every 

 great ocean current must have its counter current, it is 

 probable that there would be a flow of cold water from the 

 * Geol. Jour. vol. v. p. 4. 



