1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 243 



sharp and peaked ridges have in some places the high inclination of 

 65° to 70°. 



When viewed longitudinally in the little valley of Weissbad, nothing 

 can be more striking than the aspect of these bold tertiary peaks on 

 the one hand, and the massive cretaceous precipices on the other, 

 under which they seem to dip*. Examination, however, shows an 

 enormous void between these two classes of rocks. The upland valley 

 is indeed encumbered with much detritus, as is frequently the case 

 along such lines of fault, and for the most part fragments only of dis- 

 membered fly sell, with a rare specimen of nummulite limestone, are to 

 be seen as memorials of the vast destruction of intervening rocks 

 which has occurred. In one spot, however, at a little cascade under the 

 Thurm, one of the buttresses of the Sentis, I detected a portion of the 

 flysch, which is fairly bent under the cretaceous masses of the moun- 

 tain, which I believe to represent the sewer-kalk or chalk ; for in the 

 heights above this cascade. Prof. Brunner and myself reached, after 

 some peril and labour, a zone of secondary green sandstone. M. Escher 

 has, indeed, showTi that the chief culminating masses are sewer-kalk 

 or chalk based on greensand and neocomian. That author pointed out 

 to me, that the Sentis group is not merely a double or triple chain, but 

 is made up of six lines of ridges, in which the greensand'^nd chalk are 

 repeated with supracretaceous troughs. He has drawn for me the dia- 

 grams in the annexed plate (PI. VIL), which are the result of his long 

 and patient examination of this remarkable tract. These transverse 

 sections, made at short intervals from each other, will explain better 

 than pages of description, how the apparent alternation of formations, 

 whose denuded edges crop out to the surface, is due to folds, the axes 

 of which, though occasionally vertical, are usually oblique or inverted 

 towards the high chain of the Alps, and thus often present their 

 chief escarpment to the hills of younger tertiary conglomerate. By 

 this arrangement, nummulitic eocene rocks {f, g) dip for the most part 

 under strata of anterior age ; and whilst, on the S.E. face of the 

 mountain, they plunge towards the Alps (there regularly overlying 

 the chalk and greensand), on the north-western side they are trun- 

 cated between the molasse (in) on the one hand and the cretaceous 

 rocks {a, b, c, d) on the other, but usually dipping under the latter. 



Another most instructive section, and parallel to the above, is that 

 which proceeds from the molasse and nagelflue, the mountain called the 

 Speer (fig. 14, p. 200) on the N.N.W. across an inverted, inclined axis, 

 which clearly exposes nummulite rocks and sewer-kalk on either side 

 of a nucleus of neocomian limestone ; whilst by another fold the whole 

 series up to the flysch is displayed in a lofty basin, where the ino- 

 ceramus limestone rises rapidly into the lofty mountain Lyskamm, 

 from which, after some undulations, we see a regular descending order 

 through the whole cretaceous rocks and the Jurassic system of this 

 region, as displayed in the cliffs on the north side of the lake of 

 Wallenstadt. 



If each Alpine region be examined in detail, and its geological fea- 



* See fig. 14, p. 200, and plate of M. Escher's Sections, pi. vii. In the latter 

 the six ridges alluded to are numbered i. to vi. I have pointed out the transition 

 bed (e) and have distinguished the eocene from the cretaceous. — R. I. M. 



