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It appears to show evidence of having been subjected to great 

 pressure. We know of nothing except this ancient ice cap, which 

 could have exerted this pressure, yet we can scarcely consistently 

 allow that if this shroud of ice has the power to smooth every 

 protuberance, to widen and deepen valleys, and even grind out 

 immense lake basins, that with still greater facility it would not 

 carry with it all loose non-compact matter, and prevent any such 

 accumulation except in protected hollows. So many of our 

 difficulties would be removed if we could only see the formation 

 of boulder clay going on. We may examine limestones, sandstones, 

 and slates in their most incipient stages ; but though such immense 

 areas are covered with boulder clay, and doubtless deposits are 

 now being made, yet there is not one authenticated case of boulder 

 clay having been seen in process of formation, nor has it ever been 

 noticed in siti),, with ice in whatever form resting upon it. It is 

 nearly always impossible to examine in the smallest degree the 

 lower portions of glaciers or of sheets of ice ; but so far as has 

 been observed, it is not known that anything intervenes between 

 them and the subjacent rock, with the possible exception in a few 

 cases of an assumed "pavement," or consolidated bed of rolled 

 stones. Then in examining glaciated countries, the smooth 

 rounded contours, with the striated markings on the polished 

 rocks, are surely more probably the results of the passage over 

 them of enormous volumes of ice, containing isolated embedded 

 stones which would account for the striae, rather than that a 

 confused bed of clay and stones had been dragged across the 

 surface by the unceasing movement of the restless mass above. It 

 is possible when land ice descends from high ground and debouches 

 on a level plain, that its progress may be much checked and its 

 speed much lessened, which would necessitate that the ice on the 

 lower levels should thicken correspondingly, and that thus in some 

 way a deposit beneath might be formed ; but even this supposition 

 is fraught with many difficulties, and may hardly be tenable. 

 However slowly the ice moved, it still would move, and the under- 

 lying clay with it. If so, we should have this further question to 

 deal with. It is believed that during the glacial epoch there were 



