1899] 



THE DEVELOPMENT OF RIVERS 



277 



divide in a slight depression. The Coin had formerly taken off the 



head-waters of this Windrush 



branch. 



Professor Davis ('/) gives 

 an example : — A branch of the 

 Meuse and a branch of the 

 Toul (Moselle) opposite. 



This brings me to another 

 matter — passes and depressions 

 often produce the feature of 

 breached escarpments. What 

 is the significance of breached 

 escarpments, and what do they 

 point to in the way of river 

 restoration ? To understand 

 them it is necessary to classify 

 them, bearing in mind that 

 mainly they represent beheaded 

 valleys. According to the 

 history of the valleys they 

 have to be classified. There 



are : — 



I. Valleys opening out 

 headward on a plain. A 

 stream drains the plain, and 

 perhaps more beyond ; and it 

 flows down the valley with the 

 dip. Examples : — The Goring gorge ; 



Fig. 2. — Sketch map of the present arrangement of 

 the Severn and its tributaries near Gloucester. 

 The dotted lines indicate the supposed courses 

 of the original consequents. From the Ordnance 

 Survey, Scale, 1"=4 miles. 



the breach in the Chalk 



c 



Fig. 



3. — Section of valley crossed by divide at A. B is beheaded consequent stream, C is the 

 obsequent stream. D is the original level of the floor of the formerly extended valley 

 of the consequent. This really shows what I have termed a duplicate valley (6). Above 

 D B is one (the original valley) ; D A C is the second valley. The inclined lines show 

 dip of strata (exaggerated). 



escarpment at Upavon, where the Salisbury Avon enters, draining the 

 Vale of Pewsey. 



II. The valley is similar, but no stream flows through it. If it 

 holds a stream at all it is only in the lower part. Example : — The 



