232 FRAGMENTS OF SCIENCE. 



work, both tending to obliterate the lake the raising 

 of its bed by the deposition of detritus, and the cutting 

 of its dam by the river. In process of time the cut 

 deepened into the Via Mala; the lake was drained, and 

 the river now flows in a definite channel through the 

 plain which its waters once totally covered. 



From Tusis I crossed to Tiefenkasten by the Schien 

 Pass, and thence over the Julier Pass to Pontresina. 

 There are three or four ancient lake-beds between 

 Tiefenkasten and the summit of the Julier. They are 

 all of the same type a more or less broad and level 

 valley-bottom, with a barrier in front through which 

 the river has cut a passage, the drainage of the lake 

 being the consequence. These lakes were sometimes 

 dammed by barriers of rock, sometimes by the moraines 

 of ancient glaciers. 



An example of this latter kind occurs in the Rosegg 

 valley, about twenty minutes below the end of the 

 Eosegg glacier, and about an hour from Pontresina. 

 The valley here is crossed by a pine-covered moraine 

 of the noblest dimensions; in the neighbourhood of 

 London it might be called a mountain. That it is a 

 moraine, the inspection of it from a point on the Surlei 

 slopes above it will convince any person possessing an 

 educated eye. Where, moreover, the interior of the 

 mound is exposed, it exhibits moraine-matter detritus 

 pulverised by the ice, with boulders entangled in it. 

 It stretched quite across the valley, and at one time 

 dammed the river up. But now the barrier is cut 

 through, the stream having about one-fourth of the 

 moraine to its right, and the remaining three-fourths 

 to its left. Other moraines of a more resisting charac- 

 ter hold their ground as barriers to the present day. 

 In the Val di Campo, for example, about three-quarters 

 of an hour from Pisciadello, there is a moraine com- 



