Mr ITufjh Miller on River- Terr acinr/. 283 



gigantic potency will leave their deposits — not within the 

 shelter of comparatively small bends and loops such as con- 

 stitute the windings of modern rivers, but at larger curves — 

 possibly the very largest in the whole course of the valley. 



Terrace-Formation. 



The methods by which river-terracing is accomplished 

 having now been sufficiently examined, we proceed to look 

 into the prosecution of these methods, and the terraces in 

 which they result. So far as possible we adopt l*rofessor 

 Edward Hitchcock's classification. 



Lateral Terraces : 1. Amphitheatre Terraces at Persistent 

 Bends. Glacis Terraces. 



As we have seen, there are in every stream numbers of 

 what may relatively be regarded as persistent bends, asso- 

 ciated with others which may be viewed as comparatively 

 shifting ones. Of the persistent bend we have the best 

 example when a stream sweeps round the circumference of 

 a deep curve, bounded on its convex side by a high bank of 

 rock or boulder- clay, amphitheatre-like in aspect, and not 

 least so in that the opposite or alluvial side is often benched 

 with terraces rising in succession from the water's edge. 

 These persistent bends^ it need hardly be said, are working 

 into the bank in the direction in which they belly. 



AVhile the stream is extending the curve at its circum- 

 ference, a formation of gravel and alluvium keeps pace, as has 

 been described, at its inner or sheltered side. In numberless 

 cases that side seems to have enlarged by crescent-shaped 

 additions. Accretion is not uniform. A gravel bank is 

 sometimes piled up in a single flood around the margin of the 

 curve, and, thinning at the ends, is crescentic in form. In 

 cases where the stream-curve is deep and lobe-shaped, this 

 process may be likened to a sort of toe-capping. The line of 

 weakness between the capping and the body of the foot is 

 liable to be used in floods as a secondary channel, the cap 

 being then turned temporarily into an island. The more 

 eligible lines of weakness may be retained in use for a con- 



