324 Professor Sedgwick and Mr. Murchison on the 



Chap. II. 



A Series of Transverse Sections, intended to explain the Connexion of the 

 Secondary/ and Tertiary Systems of the Eastern Alps, 5fc. 



] . Transverse Section through the Formations near the Head of the Lake 



of Constance *. 



On the east side of the lineofsection^ the tertiary system, composed of great, 

 alternating masses of sandstone, marl, and coarse conglomerate, rises into hills 

 of considerable elevation, which form the parting of the waters of the Rhine, 

 and of the last ramifications of the Danube. The prolongation of these masses, 

 towards the west, is interrupted by the wide chasm through which the Rhine 

 makes its way into the Lake of Constance ; and in consequence, the hills rang- 

 ing along the eastern extremity of the lake, give a succession of transverse 

 sections on an enormous scale, in which the structure and relations of some 

 portions of the tertiary groups are finely exhibited. 



Our present section commences ten or twelve miles south of Bregenz, with 

 the secondary, calcareous rocks on the right bank of the Rhine, which, after 

 rising into the Stauflen and some other finely pointed summits, rapidly descend 

 into the plains, and, near their base, present some great, mural escarpments 

 singularly marked by contorted lines of stratification. From the base of these 

 precipices, a chain of low hills, almost buried under transported materials, 

 extends about a mile and a half to the village of Obersdorf, where a moun- 

 tain torrent works its way through a great ravine into the plains bordering 

 on the lake. 



The valley of Obersdorf is shut in, towards the east, by a mountain ridge 

 called the Rexberg, ranging nearly north and south, and connecting the pre- 

 cipices of secondary limestone with the ridges of molasse and conglomerate. 

 The geological features of these mountains are obscure ; but we conceive that 

 the secondary and tertiary formations, meet not far from the northern extre- 

 mity of the Rexberg ridge ; and, in that case, their place of junction must be 

 at a great elevation above the level of the Lake of Constance. 



The precipices forming the north flank of the Stauffen rest on black shale, 

 which at Haslach is obscured by great blocks of limestone fallen from the es- 

 carpments above, and containing innumerable Nummulites. Of these blocks, 

 some are light grey and compact, like the commonest limestone of the Alps ; 

 others are of a dark blue colour, and resemble mountain limestone ; some are 



* Plate XXXVI. fiff. 3. 



