ALPINE SCULPTURE. 231 



The character of the erosion depends upon the rock 

 as well as upon the river. The action of water upon 

 some rocks is almost purely mechanical; they are sim- 

 ply ground away or detached in sensible masses. 

 Water, however, in passing over limestone, charges it- 

 self with carbonate of lime without damage to its trans- 

 parency; the rock is dissolved in the water; and the 

 gorges cut by water in such rocks often resemble those 

 cut in the ice of glaciers by glacier streams. To the 

 solubility of limestone is probably to be ascribed the 

 fantastic forms which peaks of this rock usually as- 

 sume, and also the grottos and caverns which inter- 

 penetrate limestone formations. A rock capable of 

 being thus dissolved will expose a smooth surface after 

 the water has quitted it; and in the case of the Via 

 Mala it is the polish of the surfaces and the curved hol- 

 lows scooped in the sides of the gorge, which assure us 

 that the chasm has been the work of the river. 



About four miles from Tusis, and not far from the 

 little village of Zillis, the Via Mala opens into a plain 

 bounded by high terraces. It occurred to me the 

 moment I saw it that the plain had been the bed of an 

 ancient lake; and a farmer, who was my temporary 

 companion, immediately informed me that such was 

 the tradition of the neighbourhood. This man con- 

 versed with intelligence, and as I drew his attention to 

 the rolled stones, which rest not only above the river, 

 but above the road, and inferred that the river must 

 once have been there to have rolled those stones, he 

 saw the force of the evidence perfectly. In fact, in 

 former times, and subsequent to the retreat of the 

 great glaciers, a rocky barrier crossed the valley at this 

 place, damming the river which came from the moun- 

 tains higher up. A lake was thus formed which poured 

 its waters over the barrier. Two actions were here at 

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