Yol. 55.] GEOLOGY OF THE DAVOS DISTRICT. 393 



where the railway-cutting and the road are in close proximit}', 

 the serpentine is typically exposed. It disappears under the mass 

 of moraine-material that lies between the Schwarzsee and the river, 

 but will be found again high up on the shoulder of the spur 

 between the Lareterthal and the Upper Pratigau, above the 

 Eiitiwald. The thickness of detrital material renders it difficult 

 to fix on the exact point at which it crosses the Lareter Bach, but 

 it must be nearly opposite the chalets of Eied. The patch 

 between Selfranga and Klosters, with its limestone and Yerru- 

 cauo, is, I believe, a great displacement or slip from above, and 

 has no relation to the real outcrops of the different strata. From 

 the angle of the hill above Eiiti the band of serpentine drops steeply 

 down to the east of Auje, and rises again obliquely across the 

 Ehatikon to the west of Monbiel, where, so far as this area is 

 concerned, it iinall}^ disappears. 



The rock itself is a typical serpentine, and differs little from that 

 of numerous other localities. Dr. Ball has made it the subject of 

 detailed study, and has shown that it must be regarded as an 

 altered holocrystalline rock originally consisting of olivine, enstatite, 

 and diallage, and therefore to be included under the heading of 

 Iherzolite. The more crystalline varieties pass by gradation into the 

 completely altered form ; in places, as on the Parsenn-Eurka Pass, 

 the crushing which the rock has undergone has produced numerous 

 shining, slickensided surfaces and an almost fibrous structure ; 

 elsewhere the rock is traversed by veins of chrysotile and by cracks 

 infilled with ealcite. In the latter case we have a transition to 

 the mixed limestone and serpentine, or ' ophicalcite,' which is con- 

 spicuous in parts of the Todtalp district and above Monbiel. This 

 rock occurs only near the lower edge of the serpentine, and is in close 

 association with the ' mixed rocks ' to which it is now necessary to 

 refer. 



(ii) The ' Eed-and-green Schists.' 



In the immediate neighbourhood of the serpentine of the Eastern 

 Alps occurs almost invariably a series of more or less schistose rocks, 

 of varying composition, which are coloured pale green in Theobald's 

 map and lettered as ' Sv.' or ' Eothe u. Griiue Schiefer.' 



Green schists seem to predominate in other areas, and it is often 

 stated that the serpentine is intrusive in the ^ Griine Schiefer.' The 

 typical ' Griine Schiefer ' are, apparently, not present in the Davos 

 district, but there occurs instead a remarkable group of rocks lying 

 below the serpentine and extending across the Parsenn slopes and 

 the gorge of the Stutzbach. Along this zone the ' ophicalcites ' 

 into which we have traced the serpentine pass into beds in which 

 the serpentine-layers alternate with reddish calcareous bands, or 

 with red layers of an argillaceous character. It is not a case of 

 regular alternation producing a definite banded structure, but a 

 complete confusion of the three elements : the green patches of an 

 evidently serpcntinous nature, the limestone-fragments, and the 

 clayey films. 



