78 
SCENERY OF SWITZERLAND. 
berg near Matt are well-preserved remains of fish 
belonging to the genus Lepidotus. Agassiz thought 
he could distinguish, and described, six species, but 
Wettstein has shown that they all belong to one and 
the same, and that the differences of form are 
merely due to the position in which the specimens 
c 
a- 
Fig. 
happened to lie with reference to the direction of 
pressure. 
In many cases the pressure has produced 
“cleavage,” and turned the rocks into slate,* so that 
they split into more or less perfect plates or films. 
The direction of cleavage is quite independent of 
* English geologists apply the term “shale” to rocks which 
split along the laminae of original deposition, and which are 
comparatively soft and destructable, and “slate” to those where 
the lamination is due to cleavage. Continental geologists gener- 
ally include shales and slates under the same name. 
