152 ELEMENTARY GEOLOGY 
some of the soil, particularly if they are operating on 
a steep incline. As a result of rain erosion, the soil in 
many places is washed away as fast as it forms. This 
action causes a constant migration of the soil particles 
down the hillside (Fig. 76); and at the base, where 
the slope decreases, this product of the rain-wash 
gathers into a deep accumulation. In many parts of 
the arid West, one may 
see stone walls partly 
buried beneath this 
wash, which has accu- 
mulated during the 
short time that they 
have been standing. 
Nearly everywhere 
this rain-wash is 
one of the important 
Diagram to illustrate creeping of soil down the ; 
hillside. Formed by weathering, it gradu- Means by which rivers 
ally moves down, accumulating near the 
base of the hill. 
Fic. 76. 
are given sediment to 
bear away, and it is 
also one of the means by which the surface of the land 
is slowly worn down. ‘That this is so, every one can 
see for himself by watching the streams during a 
heavy rain, especially if the water enters the river 
after passing over roads and fields. The tiny rills 
become laden with mud, and soon the river is trans- 
formed to a muddy torrent. 
