ACTION OF RIVERS. 
201 
flatten them, owing perhaps to the gradual enlarge- 
ment of the gathering-grounds. 
These cones are favourite sites for villages, which 
are thus raised and placed above the range of 
ordinary floods. The loose materials of the upper 
part of the cone, moreover, absorb water freely in 
the upper part, which is filtered, and emerges in 
clear springs lower down. Thus arise many of the 
fountains in such villages. 
Now let us suppose that the force of a river is 
again increased, either by a fresh elevation, or locally 
by the removal of a barrier, or by an increase in 
volume owing to an addition of territory, or greater 
rainfall, it will then again cut into its own bed, 
deepening the valley, and giving rise to a rapid, 
which will creep gradually up the valley, receding of 
course more rapidly where the strata are soft, and 
lingering longer at any hard ridge. 
The old plain of the valley will form a more or 
