WEATHERING 127 
Any kind of rock finds protection in the soil and 
forest covering. Where bare rocks are exposed to the 
weather, the waste is most rapid. This finds illustra- 
tion on lofty peaks, which reach into the colder regions 
of the upper air, and also upon the precipitous cliffs of 
many river gorges and mountain precipices. 
Importance of Weathering. — The importance of 
weathering is great and varied. It causes the rock 
to crumble, and the surface of the land to melt down; 
and in many parts of the world it furnishes the 
soil; but if some of the decayed rock were not re- 
moved, this soil coating would soon so encumber and 
protect the rock, that the wearing down of the surface 
would be extremely slow. 
In reality, weathering goes hand in hand with 
another process, which is commonly called erosion. 
By wind, stream, or ocean, and even in some places 
by ice, fragments of rock are removed and eventually 
deposited in the sea. Nature does not separate the 
processes of weathering and erosion. We divide them 
here merely for the purpose of clear description. Rocks 
decay, the fragments are in part removed, and the ero- 
sive agents, which carry them still further, aid in the 
reduction of the level of the land. 
This combined action is denudation ; and at all times 
the various agents codperate in the task of lowering 
the level of the land and placing the waste in the sea. 
