Structure of the Eastern Alps. 381 



many fossils, especially large oysters. The oyster-beds are surmounted by 

 beds of pebbles ; which are, in turn, surmounted by blue clays and marls 

 with Cerithia and other tertiary shells. 



The oysters and other shells are not perhaps specifically the same with the 

 fossils found in the marls and sands immediately overlying- the chalk in this 

 country ; neither do we venture to affirm that any of the beds of this section 

 are perfectly contemporaneous with our formation oi plastic clay. They do, 

 however, in their internal structure, their grouping-, their fossils, and their 

 position upon the inferior cretaceous rock, present a most perfect analogy to 

 the strata overlying- the chalk at Reading, Woolwich, and other well-known 

 places in this country. 



The preceding facts seem to prove, unequivocally, that the neighbouring- 

 primary mountains of Bohemia have undergone no great movement of eleva- 

 tion since the deposition of the chalk. But the conclusion does not rest here : 

 for, as we pass round the south-western skirts of the chain^ we find the Jurassic 

 limestone, on like ground, in an undisturbed, horizontal position : we there- 

 fore conclude, that the chain has not been elevated since the period of the 

 Jura limestone. 



' It will be seen by an inspection of the map *, that the primary chain of 

 Bohemia, and the principal chain of the Alps, converge towards the east : 

 the former ranging from N.W. to S.E; the latter from S.S.W. to N.N. E. 

 According to the comprehensive theory of M. Elie de Beaumont, these two 

 lines of direction indicate two distinct periods of elevation ; and he places, 

 theoretically, the elevation of the Bohemian chain in a period immediately 

 subsequent to the deposition of the new red sandstone ; while the last great 

 movement of the Eastern Alps is supposed to have taken place after the com- 

 pletion of some of the newest, known, tertiary formations. It is obvious that 

 these grand and general views are in perfect accordance with many of the 

 facts stated in this and the preceding chapters. 



There are, perhaps, no physical phenomena, within the limits of the whole 

 region we are describing, more striking than this entire geological separation 

 of the Alpine and Bohemian chains, though ranging at so short a distance 

 from each other. 



* Plate XXXV. 



