of Valleys and Lakes, 303 



ferent reasons, also held by De Mortillet — viz. that a glacier of 

 sufficient thickness could not only fill a lake, but could flow up 

 the low angle of the ascent towards the outflow and escape 

 beyond its bounds*. 



If a glacier can round, polish, and cover with striations the 

 rocks over which it passes — if, flowing from its caverns, it can 

 charge rivers thickly with the finest mud, then it can wear away 

 its rocky floor and sides. Here indeed an appeal to nature may 

 safely be made, and the answer will be easily obtained ; for, 

 standing on the surface of scores of glaciers, such as those of the 

 Aar, and casting the eye upward, the whole mountain-sides are 

 moutonnhy and parallel striations running along and down the 

 valley are universal ; and not there alone, but miles and miles 

 below the end of the puny glaciers of today the signs of the 

 same wearing actions of grander ice-streams are visible both in 

 and thousands of feet above the present bottoms of the valleys. 

 It needs no subtle argument to prove it. Nature proclaims it ; 

 we have but to open our eyes and look upon it to see that ice 

 grinds, and has ground and planed away the surface of rocks, as 

 surely as a planing machine cuts iron, and for much the same 

 cause. "What more," says Hutton, writing of analogous waste, 

 " what more is required ? Nothing but time. It is not any part 

 of the process that will be disputedf ; but after allowing all the 

 parts the whole will be denied ; and for what ? only because 

 we are not disposed to allow that quantity of time which the 

 ablution of so much wasted mountain might require." " Time," 

 says Playfair, " performs the office of integrating the infinitesimal 

 parts of which this progression is made up ;" and though I have 

 in this Magazine formerly attempted to show, for purely geolo- 

 gical reasons, that the greater valleys in the Alps existed before the 

 so-called glacial period, yet I know perfectly well, not only that 

 since that time glaciers have worn a vast quantity of matter out 

 of them, but that, given sufficient time, a glacier of itself might 

 scoop out a valley of any depth, just as running water may do 

 the same, or as surely as that, given sufficient time, the sea will 

 wear away any island, soft or hard, large or small, that rises 

 amidst its waves. 



In further proof of the assertion that glacier-ice can have no 

 serious effect in wearing away its bottom, great stress is laid on 

 the well-known fact that such short and steep glaciers as those 



* Unless I am much mistaken, geologists will some day be much sur- 

 prised at the size and kind of hills that they will be obliged to allow that 

 glaciers have travelled over. 



t Things, however, that he considered almost self-evident are now dis- 

 puted every day. The tendency of opinion begins to set in the opposite 

 direction. 



