THE ICE AGE AND ITS WORK 



phenomena seem to be due to the great confluent ice- 

 sheet during the various phases of its advance and its 

 passing away. 



Sir Henry Howorth, in his very instructive work al- 

 ready quoted, denies the existence and even the possibility 

 of such ice-sheets as those here indicated as having occurred 

 in North America and Europe. He maintains that ice of 

 the requisite thickness could not exist, as it would be 

 crushed or liquefied by its own weight ; and further, that 

 if it existed it could not possibly move over hundreds of 

 miles of generally level country, passing over hills and 

 valleys and carrying with it, either on its surface or in its 

 lower strata, the enormous quantity of boulders, gravel, 

 and clay which we find everywhere overlying the present 

 surface of the ground. No doubt the difficulty does seem 

 an enormous one, but I think that it can be shown to be 

 not so great as it seems ; and it is certainly by no means 

 so insuperable as that of the apocryphal floods, or '' waves 

 of translation " as they have been called, to which he im- 

 putes the phenomena. He asks us to believe in one or 

 more gigantic waves sweeping over Eastern North America, 

 carrying boulders to the summit of Mount Washington, 

 nearly 6,000 feet high, scattering others over an area which 

 is roughly 1,000 miles from east to west and 600 from 

 north to south, and in its course producing those wonderful 

 striae, grooves, and furrows in the rocks photographed in 

 the American reports, and the enormous extent of smoothed 

 and rounded rock surfaces that is found over this wide 

 area. 



But, besides these, there are two other phenomena abso- 

 lutely inconsistent with a diluvial agency. One is the 

 enormous deposits of fine compact clay bearing rounded 

 and scratched stones thickly scattered through it, utterly 

 unlike any deposit produced by water, which would neces- 

 sarily leave the stones hundreds of miles behind the place 

 to which the fine mud would be carried. The other is 

 the existence of well-defined heaps, mounds, and ridges of 

 gravel and boulders, forming the terminal moraine of the 

 ice-sheet. This is exactly similar in general form and 

 structure to the moraines left by the old Alpine or North 



