CORRASION BY GRAVITY STREAMS. 



245 



Fig. 8. 



(C) 



Figures illustrating some methods adopted by streams in enlarg- 

 ing the channel (and valley) cross-section so as finally to harmonize 

 the stream velocities. Uniformity of stream velocity works 

 towards uniformity of channel slope. 



tunity to render its velocity more uniform, and that is by 

 enlarging itsjcross-section. The method of such enlarge- 

 ment on negligible slopes and deep and constricted channels 

 is by lowering the whole channel base ; by excavating 



