Vol. 50.] CRYSTALLINE SCHISTS IN THE LEPONTINE ALPS. 291 



(4) phyllite; (5) marble or calc-schist (this, I believe, corresponds 

 with the mass which is quarried behind the church) ; (6) lime- 

 stone (?) and schistose quartzite (examination of the hand-specimens 

 does not enable me to decide whether these belong to the crystalline 

 group or to the slaty sedimentaries) ; (7) gneiss ; (8) limestones with 

 phyllites — Jurassic ; (9) soft, whitish calcareous rook, possibly 

 rauchwacke ; (10) gneiss ; (11) phyllite, which alternates with 

 gneiss or crushed crystalline schists, over about 520 metres (the 

 latter dominating), after which the crystalline series becomes 

 continuous and bears a general resemblance to that crossed on the 

 ascent from Hospenthal to the St. Gothard. The northern part of 

 this section would correspond with the upper section seen at 

 Altkirche, if we may suppose the phyllite (2) to underlie the turf 

 between the outcrops of the northern gneiss and the first rib of 

 marble, which is not improbable. Of (7), which is labelled and 

 appears to be a gneiss, I have not seen any sign at the surface. 

 The limestones with phyllites (8) no doubt belong to the southern 

 part of the Jurassic band. The remainder of the section from (10) 

 onwards, which I have not quoted in detail, corresponds with the 

 sericite-gneiss, the dark phyllite or schistose slate, and the Hos- 

 penthal schists (which appear to be more gneissose than they are 

 about Hospenthal). 1 But this alternation of phyllites and crystalline 

 rocks, so far as I have seen, is not visible on the surface. Thus the 

 tunnel-section confirms the observed differences between the sections 

 at Altkirche, and indicates a still more frequent intercalation of 

 slightly modified sedimentaries with crushed crystallines than is 

 shown at the surface. Also it exhibits, west of the lower section 

 at Altkirche, a repetition of the marble, which is seen east of it at 

 the surface. This strange variation in the number of times that 

 the marble occurs is favourable to the hypothesis that the apparent 

 interstratification of the crystalline and non-crystalline groups is the 

 result of thrust- faulting, such as has been described by the members 

 of the Geological Survey in the North-western Highlands. It must, 

 however, be admitted that the ' slicing ' demanded by this hypothesis 

 is of a most remarkable kind, for the tunnel at Altkirche is at the 

 very least more than 1000 feet below the surface, so that the ' wedges ' 

 of the older rocks driven through the newer must be unusually 

 long and thin. 



(c) Section ivest of Altkirche. — This is on the left bank of the 

 Reuss, about a mile away from the last one. The fissile micaceous 

 gneiss, which forms, as usual, the northern boundary of the sedi- 

 mentary belt, crops out about 100 feet above the level meadows. 

 Near the actual junction, the exact position of which is difficult to 

 determine owing to the condition of the rocks and the presence of a 

 large quartz-vein, begins a section, practically continuous, which 

 can be followed down almost to the meadows. It exhibits a dark 



1 I have not examined a good seciton of them near Andermatt, where, so far 

 as I remember, they are generally not well exposed. 



