396 CAUSES OF CL1MATAL CHANGE 



becomes increasingly unsatisfactory as the phenomena are 

 developed into fuller appreciation. The more we consider 

 the asymmetry of the ice distribution in latitude and longitude, 

 and its disparity in elevation, the more difficult it becomes 

 to explain the phenomena upon any astronomical basis. If 

 we were at liberty to disregard the considerations forced upon 

 us by physicists and astronomers, and permit ourselves simply 

 to follow freely the apparent leadings of the phenomena, it 

 appears at this hour as though we should be led upon an old 

 and forbidden trail, the hypothesis of a wandering pole. It 

 is admitted that there is a vera causa in elevations and de- 

 pressions of the earth's crust, but it is held inadequate. It 

 is admitted that the apparent changes of latitude shown by 

 the determinations of European and American observatories 

 are remarkable, but their trustworthiness is challenged. Were 

 there no barriers against free hypotheses in this direction, 

 glacial phenomena could apparently find adequate explanation ; 

 but debarred as we doubtless should consider ourselves to 

 be at present from this resource, our hypotheses remain 

 inharmonious with the facts, and the riddle remains unsolved." 



It should be observed here that the unsolved " riddle " is 

 that of a continental ice sheet. This, as we have already seen, 

 is probably insoluble in any way, but fortunately needs no 

 solution, being merely imaginary. If we adopt a moderate 

 view as to the actual conditions of the Pleistocene, the geo- 

 graphical theory will be found quite sufficient to account for 

 the facts. 



Let it be observed here also, in connection with the above 

 thoughtful and frank avowal of one of the ablest of American 

 glacialists, that the geographical theory provides for that 

 " asymmetry "'or irregular distribution of glacial deposits to 

 which he refers ; since, at every stage of continental elevation 

 and depression, there must have been local changes of cir- 

 cumstances; and the same inequality of temperature in identical 



