240 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



of the calcareous formations better exhibited than in the Altorf branch 

 of the Lake of the four cantons, — that noble transverse fissure which 

 penetrates so far into the heart of the chain (see fig. 12, p. 195). On 

 the mountain slopes (often vertical precipices) on both sides of this 

 deep cleft, various formations from the Oxfordian or Upper Jura (o), 

 near the water's edge (Tell's Chapel), through the lower and upper 

 neocomian, greensand, gault, and sewer-kalk, or equivalent of the 

 chalk, up to the nummulitic and flysch rocks, are all seen to be twisted, 

 and often conformably to each other, in numerous flexures, which 

 increase in rapidity and intensity (in the Achsenberg for example) as 

 you approach the centre of metamorphism (or towards St. Gothard), 

 and decrease as you recede from it. In other words, the folds open 

 out into broader and less complicated sweeps in proceeding from the 

 north slope of St. Gothard as a centre to the flanks of the chain, 

 where they expand into the canton of Lucerne. Some of these ex- 

 traordinary appearances near Altorf and in the escarpments of the 

 adjacent lake have been figured in two coloured diagrams by Dr. 

 Lusserf. Faithfully delineating what he saw, and judging from the 

 order of superposition, that author concluded, that rocks with green 

 earth and nummulites were repeated several times over in the series, 

 and that these fossils existed in strata (occasionally crystalline) of 

 considerable antiquity, as well as in younger beds. The effort which 

 Dr. Lusser made to classify the rocks of this disturbed tract by mi- 

 neral characters and appm^ent order of superposition has, I need 

 scarcely say, proved invalid ; for as soon as you extricate the nummu- 

 litic zone from the labyrinth in which it is involved in the Achsenberg 

 near Altorf (see fig. 12, p. 195 ante) and follow it out towards the 

 N.N.W., it is seen to fold regularly over upon the surface of the 

 cretaceous rocks, first in the sharp and partially broken synclinal of 

 Syssikon, then in the dome or anticlinal of the mountain above Brun- 

 nen, and next in the broader synclinal of the valley of the Muotta. 



The precipitous faces of rock on the sides of the lake of Altorf 

 are indeed most instructive, in showing us the intimate connection 

 between the chief axial line, the folds of the strata and the lines of 

 fracture. In one portion of the lake, nearly midway between Brun- 

 nen and Fluelen, the centre of the folds of one of the masses appears 

 in the opposite cliffs, and thus marks the general strike of such con- 

 tortions to be parallel to the axis, or E.N.E. and W.S.W. ; whilst a 

 line of fracture equally visible on both sides of the transverse fissure is 

 also parallel to the same (see *, fig. 12). In short, the order of 

 operations seems undoubtedly to have been, first contortion and then 

 fracture ; the nuclei, or inner rolls of the folds, and the lines of dislo- 



t Nachtragliche Bemerkungen zu der geognostischen Forschung und Dar- 

 stellung der Alpen, vom St. Gothard bis am Zuger-See. Swiss Transactions, vol. i. 

 p, 44. Although he does not appear to have noticed organic remains in these 

 mountains, De Saussure has described some of their remarkable flexures and 

 breaks. He speaks of the calcareous strata of the Achsenberg as exhibiting the 

 form of the letter S several times repeated with fractures, and reminds us that 

 Valiisnieri in his * Origine delle Fontane' had remarked upon these grotesque 

 outlines. He also mentions a great bend in the form of a C from which the strata 

 extend horizontally below. — Voy. dans les Alpes, vol, iv. § ix. 1933 et seq. (see 

 my fig. 13), 



