170 AEE SOILS ENIIICIIED, IMrOYEKISIlED, n. rii. 



heavy rains. For if water can get out at one end of a 

 level channel, and cannot get out at the other end or at 

 the sides, it not only icill^ but must^ get out where it 

 can- — 



Unda impellitar unda, 

 Urgetnrqiie prior venienti urgetque priorem ; 



and it will carry with it much of the finer soil formed 

 by disintegration and vegetation. 



When these chalky downs are ploughed up, the 

 brow of the hill shows light, and the soil darkens in 

 descending. If this is not from the wash of rain, what 

 is it from ? If it is, the wash of rain must be considered 

 as a very universal agent. 



The lateral wash of rain acts constantly to fill 

 valleys. The longitudinal scooping force of rain and 

 the run of rivers constantly counteract this. But in this 

 continual contest, by comparison with their adjacents, 

 the ' lines ' of rivers and valleys are far from being de- 

 nuded. On the contrary, they are the favoured recep- 

 tacles, the permanent, rich reservoirs of soil. But, 

 according to Professor Sedgwick, they ought to be the 

 denuded parts. 



Nothing can be more pellucid than our Hampshire 

 streams, except in heavy rains ; and to look at them 

 we should not say that they carried much soil to the 

 sea. But throw a dam across the valley, and form a 

 pond. Deep mud is instantly deposited over the whole 

 bottom of the pond, and a boggy delta where the 

 stream enters. This is from the lateral wash of soil 

 into the river in heavy rains. We have only to look at 



