ALPINE SCULPTUEE. 231 



upwards from the bridge itself, the evidence of aqueous 

 erosion was equally convincing. 



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 

 simply 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 assume, 

 and also the grottos and caverns which interpenetrate 

 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 hollows 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 mountains 



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