INFLUENCE OF STRATA UPON SCENERY. 263 
our railway lines leaving London have been com- 
pelled to tunnel through the Chalk. So also m 
Switzerland the calcareous strata form long con- 
tinuous ridges, of which the great wall of the Bernese 
Oberland is a marvellous example. 
Another reason for the extremely bold character 
of the calcareous mountains is that such strata are 
extremely stiff, and where argillaceous rocks would 
gradually bend, they break away and thus give pre- 
cipitous cliffs. 
It was at one time supposed that each kind of 
rock gave its own special mountain form. Such was 
the view, for instance, even of excellent obseivers, 
such as L. v. Buch and A. v. Humboldt. 
It would, however, be quite a mistake to sup- 
pose that particular contours always indicate the 
same kind of rock. On the contrary, we find the 
same forms in different rocks, and different forms in 
the same description of rock. They depend greatly 
on the hardness of the rock, and on the angle at 
which it stands. Thus tower-like forms occur in 
Granite, Amphibolite, Sandstone, Conglomerates, 
Hochgebirgskalk, Dolomite, etc. The desk-like form 
which is so frequent in calcareous strata (see, for in- 
stance, Fig. 70 p. 266, on the right hand side) occurs 
also in some districts of Gneiss or of Nagelflue, as, for 
