Influence of Water and Ice on the Earth's Features. 357 



Either the Alps have been formed in all their main outlines 

 by convulsive elevations, or the grand outlines we see are 

 merely the harder rocks left after the removal by denudation, 

 erosion, or disintegration of the softer overlying and more 

 modern strata. There are certain remarkable gorges in 

 the Alps that at first sight seem to afford the strongest 

 possible proof of the fracture theory, and these have 

 generally been quoted as not admitting of any other explana- 

 tion than is thus afforded. Certainly the traveller, in winding 

 through the narrow gorge of Pfaffers, where the sky can 

 scarcely be seen overhead, or in climbing the steep road of the 

 Yia Mala to the Splugen Pass, may well believe that the crevice 

 he threads is the result of fracture or contraction, and that it 

 has been formed in the rock originally during elevation, and is 

 independent of all water action. Most of the wider valleys 

 present evidence of water action ; but these narrow gorges, if 

 any, must be results of fracture. 



. Visiting this part of Switzerland with the view of examining 

 into the point, Professor Tyndall has lately recorded, in the 

 Philosophical Magazine for October last, the result of his sum- 

 mer excursion. He found on the slopes of the Yia Mala stones 

 rounded by water action, masses of detritus showing perfect 

 stratification, and throughout the whole distance abundant 

 proof that the whole cleft has been cut by the river, which now 

 rushes along many hundreds of feet below. At the top of the 

 pass is a plain, which is the bed of an ancient lake, and several 

 other such, lakes can be traced on the high plains of the adja- 

 cent passes. The Via Mala is certainly a water- worn 

 fissure. 



When we calculate the amount of gaping that would be 

 produced within a given area by an elevation to the extent of 

 the Alpine summits, it is clear that the valleys that exist can- 

 not be explained by any such hypothesis. If they have been 

 originally determined by cracks formed during upheaval, of 

 which there is rarely proof, they have been so much modified 

 by water action as to justify us in referring" to that as the effi- 

 cient agent. 



It is chiefly in limestone that narrow gorges with vertical 

 walls occur. In some of these, as in the canons of the Colorado, 

 described and figured in a recent number of the Intellectual 

 Obseevee, the water origin is very clear. In others, as in some 

 of the valleys of the North of England, in the Alps and in 

 America, long lines of caverns have been eroded and worn 

 away by water till their roofs have fallen, and they offer deep 

 open channels for water. Even where the rocks are less easily 

 acted upon, but are unequal in their power of resisting water, 

 curious crevices are formed through which water runs, or has 



