THE MOUNTAINS OF SWITZERLAND. 
95 
while the inner chains are thrown 
into the most extreme contortions. 
In some cases the result of com- 
pression has been to push certain 
strata bodily over others. Such over- 
thrusts also greatly tend to render 
the relief of the surface independent 
of the tectonic structure. If there 
were no overthrusts, if the arches 
had been flatter and the troughs 
broader, the causes which have led 
to the present configuration of the 
surface would have been much 
clearer. 
The main ranges then are due 
to compression and folding, the 
peaks to erosion, and the three main 
factors in determining the physical 
geography of Switzerland, have been 
compression, folding, and denudation. 
The present configuration of the 
surface is indeed mainly the result 
of denudation, which has produced 
the greatest effect in the Central 
portions of the chain. It is probable 
that the amount which has been 
