392 ME. A. y. JENNINGS ON THE [Aug. 1 899, 



about Ardetz and the Piz Mondin, and with the outcrop at Mattrey 

 on the Erenner Pass. Those on the western side, in the Pennine 

 Alps around Zermatt, in the Yal d'Aosta, at Mont Jovet, and at 

 various localities farther south in the Cottian and Maritime Alps, as 

 far as the coast between Genoa and Pegli, may perhaps belong to 

 the same series of intrusions. 



In the Davos district the main mass of the serpentine constitutes 

 the Todtalp, which rises on the north and west of the lake, and 

 stretches westward to the Weissiluh, culminating in the precipitous 

 black crags of the Schwarzhorn (2672 metres high). The eastern 

 face of the mountain stands far back on the west of the Klosters- 

 Davos road, and is deeply furrowed Iby the numerous streams which 

 are fast eroding its green-and-purple slopes. At the foot of this 

 eastern face the talus-heaps merge into a huge detrital fan, sloping 

 eastward, and at AVolfgang overlapping the end of the pine-clad 

 ridge that crosses the valley at this point. There is every evidence 

 of the removal of an enormous thickness of rock from this side 

 of the mountain, and the striking proofs of great glaciation on 

 the barren upper plateaux, specially mentioned by Theobald, show 

 that it is not only aqueous denudation which has effected the change. 

 Between the Meierhofer Thai, which bounds it on the south, and 

 the Stutzbach, which flows from its northern limit, the serpentine- 

 mass gives the impression of vast solidity and thickness, but this 

 appearance is to some extent deceptive. There is no doubt that 

 the serpentine constitutes only the most prominent part of a band 

 dipping southward and eastward with the other strata of the district, 

 overlyiug the rocks of the Parsenn slope, and disappearing below 

 the crystallines of the Dorfliberg. On the west its sharply-marked 

 junction with the Weissfluh dolomite can be readily traced by the 

 eye from any high view-point, such as the Schiahorn ; but, though 

 it clearly crosses the Schaiiager ridge and forms a tongue-like 

 projection down the Haupterthal, it shortly disappears in the stony 

 waste of this desolate valley. This is due, I believe, to a local 

 overthrust, of which there is other evidence. 



If, however, the road down the valley towards Langwies be 

 followed, the observer will note the reappearance of the serpentine 

 on the hillside to the left beyond Kiipfen. A broad zone of the 

 characteristic colour will be seen striking obliquely across the 

 shoulder of the foot-hills, and so disappearing into the Arosathal. 

 In the latter valley its course is readily followed along the eastern 

 side to Arosa, and on the west striking across to Maran. In this 

 area it seems to lose its character as a simple band, and, as is the 

 case with the associated strata, seems to be repeated, and as it were 

 distributed in patches. This I take to be due to folding, faulting, 

 and denudation, not to the presence of separate intrusive masses. 

 Leaving it here as the limit of the district now under review, and 

 returning to the eastern foot of the Todtalp, we have to try to 

 follow it in a similar manner northward and eastward ; and the 

 task is by no means easy. 



At the sharp bend in the highway above the village of Laret, 



