88 
SCENERY OF SWITZERLAND, 
the present mountain summits are mainly the result 
of erosion and denudation. 
We will now consider the evidence which leads 
to the conclusion that the fossiliferous strata formerly 
extended over the Central chain of the Alps. It is 
a common error to suppose that the limits of 
geological strata are those which are now shown on 
the map. It requires little reflection however to 
show that this was not so. In the abyssal depths of 
the ocean deposit is portentously slow, and a long 
period would be represented by only a few inches of 
rock. Moreover, though a marine formation proves 
the existence of sea, the absence of a marine forma- 
tion does not prove the existence of land. Strata 
may and often have been entirely removed. Our 
Cretaceous deposits, for instance, once extended far 
beyond their present limits. The same was the case 
with the Secondary deposits of Switzerland from the 
I rias to the Eocene. They extended completely over 
the Central mountains. If these mountains had been 
then in existence and the Secondary strata had been 
deposited round them, we should find evidence of 
shore deposits, with remains of animals and seaweeds 
such as live in shallow waters and near land. This 
is however not the case; we find no pebble beds 
such as would be the case near a shore, no gravels 
