320 ELEMENTARY GEOLOGY 
So gradual has been the uplift, that even while the elevation 
was in progress, denudation has been able to cut down the moun- 
tain tops, and thus little by little reduce the elevation. No moun- 
tains in the world rise to the height they would have reached if 
denudation had not been relatively important (Fig. 192). So far 
as known, the loftiest mountain peak on the globe is that of 
Mount Everest in the Himalayas, which rises to a height of about 
29,000 feet above sea-level; and yet if the rocks which partially 
enwrap it were projected above, as they once extended, the eleva- 
tion of this mountain would be vastly greater than at present. 
Everest has been raised in very recent times, and there is no 
reason for believing that it previously reached many thousands 
of feet higher into the air than at present; but rather, that as it 
rose, the layers that covered it were stripped off. 
Section of a part of the high Alps. Dotted lines show the continuation of the 
folds if denudation had not reduced the mountains. 
Intermittent Growth. — It has been said above, that 
many mountains have developed again and again, and 
that their growth has been not only slow but intermit- 
tent. Of this the evidence is conclusive, bemg fur- 
nished by the frequent wnconformities (Fig. 193) among 
the mountains. A series of strata have been deposited 
in the sea, in a nearly horizontal position, and then 
folded, or faulted, and tilted into a mountain ridge. 
In the rocks are fossils which determine the age of the 
strata. (See pp. 395 and 397.) 
