LUBBOCK ON THE ANTIQUITY OF MAN. 259 



To this Mr. Hopkins sees no a priori objection ; but lie does 



not feel disposed to attach much weight to it, because it is " a 

 " mere hypothesis framed to account for a single and limited 

 " class of facts, and unsupported by the testimony of any other 

 " class of allied, but independent phenomena." 



2ndly. Admitting the proper motion of the sun, it has been sug- 

 gested that we may have recently passed from a colder into a 

 warmer region of space. 



I must refer to Mr. Hopkins' paper for his objections to this 

 suggestion, which certainly appear to " render the theory 

 " utterly inapplicable to the explanation of the changes of 

 " temperature at the more recent geological epochs." (L c. 

 p. 62.) 



Srdly. The eflect of an altered position of land and water. 



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

 much ability, would no doubt have the effect attributed to it, 

 but it seems scarcely applicable to the present difficvilty, 

 because the geography of Western Europe must have been 

 nearly the same during the period under consideration, as it is 

 at present. The existence of a continent north of Scandinavia 

 and Scotland, might indeed go far towards accounting for the 

 phenomena; but to this suggestion we must make the same 

 answer as to the first. 



4tlily. An alteration in the earth's axis. 



The possibility of such a change has indeed been denied by 

 many astronomers. My father, on the contrary, in a letter to 

 Sir C. Lyell,* has maintained that it woidd necessarily follow 

 from upheavals and depressions of the earth's surface, if only 

 they were of sufficient magnitude. This suggestion, however, 

 like the preceding, involves immense geographical changes, and 

 would therefore necessarily have required an enormous lapse of 

 time. 



Sthly. IMi". Hopkins, in the paper to which I have ah-eady alluded, 

 inclines to find another solution of the difficulty in the suppo- 

 sition that the Gulf Stream did not at this period warm the 

 shores of Europe " A depression of 2000 feet would," he says, 

 " convert the Mississippi into a great arm of the sea, of which 

 " the present Gulf of Mexico would form the southern ex- 

 " tremity, 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 Ame- 

 rican coast, but would pass directly up this channel into the 

 Arctic Sea ; and as eveiy gi"eat ocean current must have its 

 counter cvirrent, it is probable that there woidd be a flow of 



* Gcol. Jour., Vol. V. p. 4. 



