490 THE ICE AGE IN NORTH AMERICA. 



sheet. I think I speak the growing conviction of active work- 

 ers in the American field, that even the ingenious theory of 

 Croll becomes increasingly unsatisfactory as the phenomena 

 are developed into fuller appreciation. I think I may say 

 this without prejudice, as one who, at a certain stage of study, 

 was greatly drawn toward that fascinating hypothesis. 



Bat the more we know and ponder upon the enormous de- 

 velopment of ice upon the plains of northeastern America, and 

 contrast it with the relatively feeble development and disper- 

 sion from the mountainous regions of Alaska, which now bear 

 the greatest glaciers outside of the arctic regions, and the rela- 

 tive absence of such accumulations in northeastern Asia — in 

 short, the more Ave consider the asymmetry of the ice distri- 

 bution in latitude and longitude, and its disparity in eleva- 

 tion, the more difficult it becomes to explain the phenomena 

 upon any astronomical basis, correlated though it be with 

 oceanic and aerial currents and geographical features, by 

 whatsoever of ingenuity.* 



Professor Le Conte remarks, in similar strain : 



Of the recurrence of many glacial epochs in the history of 

 the earth" there is as yet no reliable evidence, but much evidence 

 to the contrary. It is true that what seem to be glacial drifts, 

 with scored bowlders, etc., have been found on several geologi- 

 cal horizons, but these are usually in the vicinity of lofty 

 mountains, and are probably, therefore, evidence of local glacia- 

 tion, not of a glacial epoch. On the other hand, all the evi- 

 dence derived from fossils plainly indicates warm climates even 

 in polar regions during all geological periods until the Quater- 

 nary. The evidence at present, therefore, is overwhelmingly 

 in favor of the uniqueness of the Glacial epoch. This fact is 

 the great objection to CrolPs theory. f 



All doubts, concerning the existence of carboniferous and 

 Cambrian glacial periods have, however, been removed by 

 facts which have accumulated during the last twenty-five 



*" Proceedings of the American Association for the Advancement of Sci- 

 ence," vol. xxxv, p. 211. 



f "Elements of Geology," p. 577- 



