252 
SCENERY OF SWITZERLAND. 
the materials which now compose the Rigi or the 
Pilatus were deposited at the bottom of the sea. 
Indeed, we may say that it is because they are so 
old that they have been so much worn down: the 
Alps themselves are crumbling, and being washed 
away; and if no fresh elevation takes place, the time 
will come when they will be no loftier than Snowdon 
or Helvellyn. 
They have already undergone enormous denuda- 
tion, and it has been shown that from the summit of 
Mont Blanc some lo to 12,000 feet of strata have 
been already removed. The conglomerates of Central 
Switzerland, the gravels and sands of the Rhine and 
the Rhone, the Danube and the Po, the plains of the 
Dobrudscha, of Lombardy, of South France, of 
Belgium and Holland, once formed the summits of 
Swiss mountains. This amount of denudation gives 
us, I will not say a measure, but at anyrate a vivid 
idea of the immense time that must have elapsed 
since the Alps rose out of the sea. 
Denudation began as soon as the land rose above 
the sea, and the main river valleys were excavated. 
Then came a period of cold known as the Ice Age 
or Glacial period. 
Round all the high mountains, and over many of 
them, are great fields of ice and snow, terminating in 
