THE ENGADINE. 
243 
hence the lateral streams have built up dams across 
the valley, thus causing the chain of lakes. 
The lake at Davos is probably due to a similar 
cause, the former head waters of the Landwasser 
having been captured by the Landquart. (See vol. i. 
p. 220). 
The Val Bregaglia and the Upper Engadine con- 
stitute, as already mentioned, one great trough 
valley. 
The west half of the Silser See and both sides 
of the Val Bregaglia as far as Nazarina are Talc 
Schists, much contorted. Isola stands on a river 
cone, formed by the stream of the Val Fedoz. The 
promontory opposite Isola is a ridge of Trias which 
runs south-west to the Piz Lunghino. Beyond it to 
the north is Serpentine; the north-east of the lake is 
Mica Schist, above which is Granite stretching from 
Piz Lungen to Piz Munteratsch, across which passes 
the Julier ' Road. It consists of white or pinkish 
Orthbclase, green Oligoclase, grey or white Quartz 
and brown Mica. These tints make it one of the 
most beautiful rocks in the Alps. The grains are of 
medium size. It crosses the valley and extends to 
Pontresina. Both the Val Roseg, and that of Mor- 
teratsch are excavated in it, and it forms a great 
16* 
