WEATHERING 121 
score or more of feet; and in some places, as for 
instance in parts of Brazil, it has reached a depth of 
one or two hundred feet. 
The section of residual soil shows very fine clay at 
the surface, where animals and plants, heat, cold, and 
water, have been longest at 
work. It grades downward 
into the fresh, intact rock, 
at first being mixed with 
large broken fragments 
(Figs. 53 and 54), and then 
changing to partly decayed 
rock in an undisturbed con- 
dition. 
Other Soils. There are 
other kinds of soil besides 
these, —such as those formed Rive 
by the wind which blows fine Fig. 53. 
: ~ } Photograph of a section of resid- 
particles hither and thither, adage : 
ual soil, showing rock fragments 
‘or by rivers. which build partly decayed in lower portion, 
deltas or floodplains, or by ee Rete 
ice which causes an accumulation of glacial soils. It 
happens that in northern United States and Europe, 
the last is the common soil. It has been transported 
by great glaciers like that now covering Greenland, 
and is not the result of rock decay (p. 484). 
Absence of Soils on Mountains. <A residual soil-cover- 
