on Serpentines in the Pennine Alps. 



535 



bretter, on which rests the Ober Theodule glacier, but also the 

 peak of the Klein Matterhorn (12,752 feet) consist. It appears again 

 on the south side of the Twins and the Breithorn, in the Val d'Ayas, 

 and patches of the same rock, sometimes of considerable size, occur 

 at intervals about the Val d'Aoste and the Graian Alps. West of 

 the above-named mass of serpentine comes a green schist which 

 is indicated on the Swiss map by a colour different from that 

 assigned to the Riffelberg schist ; but to my eye there is no marked 

 distinction between the two rocks. Serpentine also occurs in 

 isolated patches among the schists for a distance of many miles 

 in this direction, while on the north-east a kind of tongue protrudes 

 from the mass forming the Riffelberg towards the base of the 

 Findelen glacier, runs in a broad dyke-like mass on its right bank, 

 and then forms another great patch which culminates in the summits 

 of the Allaleinhorn, Rimpfschhorn, and Strahlhorn, whence it 

 extends even as far as the Fee-alp above the Saasthal. The dis- 

 tribution of the serpentine, as mentioned above, is inexplicable on 

 any other supposition than that it is an intrusive rock of igneous 

 origin, though I have not yet seen it either sending off dykes or 

 cutting distinctly across the bedding of the schists. This negative 

 evidence, however, is of little weight, for in the Alps junctions are 

 very often commonly covered up by debris, and I deemed it un- 

 necessary to spend much time in hunting for them, because evidence 

 already obtained in other localities has fully satisfied me as to the 

 history of an ordinary serpentine. 



\<mt 



ESE. 



Fig. 1. — Section through Gorner Grat. 



(1) Serpentine. (2) Green schist. (3) Calc-mica schist. (4) Quartz -schist. 

 (5) Micaceous gneiss. 



The main mass of serpentine, described above, together with the 

 enclosed hornblendic schist, measures rather more than 3^ miles 

 from E. to W. and rather less than 2J miles from N. to S. ; but if 

 we measure from the summit of the Klein Matterhorn to the furthest 

 part of the margin, in a direction rather east of north, the distance 

 is more than five miles. Thus the mass of serpentine at the head of 

 the Vispthal is not less important than that of the Lizard in Cornwall. 



Some at least of the schists through which the serpentine appears 

 to have broken must be rocks of sedimentary origin. Whatever 

 may be that of the green-schists and certain of the mica- schists and 

 gneisses in this series, it is impossible to doubt that of the quartz- 

 schist and the calc-mica schist. In the latter micaceous and calcareous 

 bands, these sometimes becoming a crystalline marble, so constantly 

 alternate, that they seem only explicable on the hypothesis of an 



