192 
ARE SOILS ENRICHED, IMPOVERISHED, [Part III 
continued rain will not run; and this run will 
be discoloured. This discolouration will be from 
soil; and this soil will be deposited where the 
rain ceases to run. 
Even where the*overflow of a river stands and 
deposits, that deposit may be subject to denu¬ 
dation from local rain after the river, or rather 
the flood, has subsided; though the deposit of 
the river may be annually in excess, and accu¬ 
mulation of soil may result, as in all alluvial 
valleys. 
But the chief thing which diminishes and re¬ 
tards the effect of the wash of rain is the very 
force of the cause. This force, speaking libe¬ 
rally, has thrown the whole surface of the earth 
into ridge and furrow, into these graduated 
vales sloping to the sea; so that all the broad 
superficial runs of this wash are shortened , and 
are made lateral , into these longitudinal channels. 
We shape our roads high in the middle on this 
principle, to throw the rain off on each side with 
the shortest possible run into the ditch or 
gutter, and to prevent a wash along the road, 
which would otherwise soon wash our artificial 
road away. Were it otherwise in nature, were 
there one plane descent from the tops of all the 
hills and mountains, the volume of the super- 
