1884.] on the Building of the Alps. 59 



of the Pennines, we see an enormous mass of distinctly bedded rock, 

 of a brownish tint, of which at this distance we should hesitate to 

 say whether we ought to regard it as a member of the metamorphic 

 or of the ordinary sedimentary series. In an E.N.E. direction we see 

 it gradually rising to form the peak of the Ofenhorn and the upper 

 part of the mountains about the Gries Pass. In the opposite direc- 

 tion it forms the lower slopes of the Simplon Pass and the portals 

 of the valley of the Yisp. Hence, could we follow it, the area 

 occupied by this rock broadens out into the spurs which enclose 

 the Einfischthal and the Eringerthal, and crosses the watershed 

 towards the south, to the east of the St. Bernard Pass. In more 

 than one locality in the region of the Binnenthal a band, of no 

 great vertical thickness, of a white crystalline dolomite is conspicu- 

 ously present. A very similar group of rocks occurs in the Val 

 Piora, in some bands of which black garnets are very abundant. 

 The same mineral also occurs in a similar rock near the summit of 

 the Gries Pass. Andalusite or staurolite also occurs occasionally ; 

 the group, in short, is well characterised, and for reference I will 

 call it the Lustrous Schists. 



I pass now to the neighbourhood of the St. Gothard. The coarse 

 gneiss, which is pierced by the northern entrance of the great tunnel, 

 ends abruptly at the Urnerloch. The basin of the Urserenthal is 

 excavated from satiny slates with dark limestones, very possibly of 

 Jurassic age, and from some underlying rather variable schists. The 

 first rock visible on the eastern side as we approach Andermatt is a 

 schistose crystalline limestone, associated with mica schists; and a 

 series of rather variable schists, evidently very different from the 

 coarse gneisses of the gorge below, apj)ears to cross the valley, and 

 form the slopes leading to the Oberalp Pass. These may be traced 

 for some distance up the Furka road above Realp, when they are 

 abruptly succeeded by the slaty group mentioned above. I am con- 

 vinced that they are much more ancient than the latter, being probably 

 members of the Lustrous Schist group, if not older. It is obvious 

 that the newer rocks are only a fragment of a loop of a huge fold, over 

 which on either hand the fragments of the enveloping older meta- 

 morphic rocks tower up in mountain peaks. On the ascent of the St. 

 Gothard Pass from Hospenthal a series of somewhat variable micaceous 

 schists continues till the top of the first step in the ascent is reached, 

 about 800 feet above the valley, when gneiss sets in, generally rather 

 coarse and sometimes very porphyritic, occasionally interbanded with 

 dark, rather friable mica schists. The upper plateau of the pass 

 consists of a porphyritic rock, often called granite, but with a 

 gneissose aspect and rather more friable in character than the rock of 

 the Wasen district. On the first steep descent on the south side this 

 rock appears to pass into a normal coarse gneiss, occasionally banded 

 with mica schist, resembling that in a similar position on the northern 

 flank, which is succeeded for a short space by a remarkably well- 

 banded gneiss. To this succeeds — it must be remembered that 



