of Valleys and Lakes. 295 



the various movements which each chain has undergone at various 

 periods" &c. The meaning of this, I conceive to be, that moun- 

 tain valleys lie in lines of curvature, dislocation, and fracture, 

 and that the mountains on each side of them are mountains, far 

 less because of denudation than by reason of operations of frac- 

 ture and dislocation. Therefore important lakes that fill true 

 rock-basins lie only in lines of fracture, or else, as in the myriad 

 lakes of North America, in hollows of wider dislocation somewhat 

 aided by subsequent denudations. 



Every reasoning mind respects authority when it bears on 

 questions that have been reduced to demonstration; but this is 

 precisely what has not been done with respect to the origin of 

 special Alpine lakes and valleys by those whose main argument 

 is disturbance of strata. Assertions and crude ideas in all kinds 

 of books and papers are " as plenty as blackberries ; 3i but for 

 clear demonstrations— none are given. Nor does Sir Roderick 

 either attempt or point to any when he says that in the Alps he 

 " long ago came to the conclusion that the chief cavities, vertical 

 precipices, and subtending deep, narrow gorges, have been ori- 

 ginally determined by movements and openings of the crust, 

 whether arranged in anticlinal or synclinal lines, or not less fre- 

 quently modified by great transversal or lateral breaks, at right 

 angles to the longitudinal or main folds of elevation or depres- 

 sion." Now in my paper I gave six stratigraphical reasons to 

 show why the lakes do not lie in hollows of disturbance, and 

 then pointed to ice as the only remaining agent by which they 

 could be formed, thus attempting to reduce the matter as nearly 

 as I could to a demonstration ; and what I want is an attempt 

 at demonstration in return. But where is the proof beyond the 

 general assertion and impression that craggy-sided mountains 

 and valleys prove dislocations which gape. If they were mere 

 close or nearly close fractures and denudation did the rest, the 

 argument is equally in favour of my view ; for valleys which have 

 been scooped out by denudation often necessarily coincide with 

 lines of fracture, a proposition obvious to every geologist. But 

 I w r ant the proof that the Alpine valleys are dislocations. Let 

 any one go into them and prove it in numerous cases, with his 

 geological map in his hand, by the arrangement of the rocks on 

 either side, and by the fracture or fault visible, or otherwise cer- 

 tainly demonstrable in the bottom. Where are these valley faults, 

 whose name ought to be legion, marked in the best geological 

 maps of Switzerland ? If they exist, they remain yet to be indi- 

 cated in definite lines ; for indeed none know better than the 

 many eminent geologists of Switzerland and the north of Italy, 

 for whom and for whose work I have the highest respect, that 

 the geological map of their country is as yet but an admirable 



