168 ARE SOILS ENRICHED, IMrOVERISHED, pt. hi. 



quite inappreciable. Still there is, perhaps, scarcely 

 any place in nature where excessive, 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 de- 

 posits, that deposit may be subject to denudation from 

 local rain after the river, or rather the flood, has sub- 

 sided ; though the deposit of the river may be annually 

 in excess, and accumulation of soil may result, as in all 

 alluvial valleys. 



But the chief thing which diminishes and retards 

 the effect of the wash of rain is the very force of the 

 cause. This force, speaking liberally, 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 superficial wash 

 of rain, increasing as it descended, would many times 

 in the year desolate the whole of the lower parts of the 

 hills and mountains ; and the lower parts of the hill- 

 sides would have less soil than the upper parts ; they 



