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SCENERY OF SWITZERLAND. 
removed is nearly equal to that which still remains,* 
and it is certain that not a fragment of the original 
surface is still in existence, though it must not be 
inferred that the mountains were at any time so 
much higher, as elevation' and denudation went on 
together. 
The country is now, however, so well mapped 
that if changes are still going on they must ere long 
show themselves. It is probable on mechanical and 
geological grounds that the southern chains were 
formed first, and the northern ones afterwards in 
order of succession. It has been shown that the 
Secondary strata originally covered the whole area, 
and their removal from the Central massives, except 
in the deeper folds, is strong evidence of their great 
age. This leads us to the consideration whether 
changes of level are still taking place, There are 
some reasons for doubting whether they have alto- 
gether ceased, but as yet we have no absolute proof. 
Slight earthquakes are common in Switzerland; 
more than 1000 have been recorded during the last 
150 years, and no doubt many more have passed 
unnoticed. This appears to indicate that the forces 
which have raised the Alps are perhaps not entirely 
* Heim, Beitr. z. Geol. A. d. Sckw., L. XXV. 
