THE ORIGIN OF DERBYSHIRE SCENERY. 



191 



the tendency of a river flowing through any flat plain would be to 

 become so. It is not difficult to see how its serpentine course has 

 been produced. A slight weakness in one of its banks permits 

 an encroachment. Gradually a concavity is formed round which 

 the water is swirled, being directed against the opposite bank. This 



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is accordingly cut back, a similar concavity formed, and the water 

 rushing round this is driven against the opposite bank ; thus the 

 action is, as it were, reflected from side to side, and a serpentine 

 course is the result Alluvium -gravel, sand, and mud- 

 accumulates opposite the concavities and reaches the surface, 

 forming a sloping and sandy bank, while the concavities are steep 

 and frequently undercut, as shown in a. This process may be 

 well seen in small streams at Duffield and elsewhere. Sometimes 

 a river will cut through the neck of land as in b at a or a', and 

 thus temporarily shortens its course. The old loop forms a lake, 

 which subsequently dries up, and may be readily detected by the 



