L. Richardson — River Development in Wales. 511 



Valley ; the hills that are grouped around the Carneddau to the 

 Cleeve-Hill plateau ; the Llansaintfread Valley to that of Seven- 

 hampton ; and the Aberedw Hill and its northern prolongation to the 

 hills that form the east side of the Sevenhampton Valley. 



Such was probably the state of the river-distribution in the Vale of 

 Gloucester before the River Severn cut its way back. 



The Severn captured the consequent that flowed from. Upton to 

 Andoversford at Tewkesbury, and brought about that river-distribution 

 which has not greatly changed at the present time. 



The River Bran, the north-easterly directed tributary of the Towy, 

 will effect in time in the Vale of Llangamarch changes similar to those 

 that the Severn has in the Lower Severn Valley. It is not difficult to 

 see that a further backward development will bring about the capture 

 of the Upper Wye ; the diversion of that portion of the Wye which is 

 above T^ewbridge into the capturing Towy-Bran River ; the resultant 

 beheading of that portion of the Wye to the south-east of the elbow of 

 capture ; to be followed by the initiation of an obsequent-stream up 

 the Builth-Wells Valley, and the recession of the source of the beheaded 

 Wye. The comparison could be carried further, but it will be easy 

 for those who know about the state of river-development in the 

 neighbourhood of Andoversford, near Cheltenham, to institute the few 

 minor comparisons that remain. 



The undulating ground that separates the progressing Bran from 

 the receding Cledan and Dulas tributaries of the Irfon is excellently 

 viewed from the lofty summit Y-Foel above Llanwrtyd Wells. On 

 the south side the ground falls steeply towards Llandovery. 



The Towy River has obviously effected an important capture at 

 Llandovery. Once no doubt the River Usk commenced its course 

 considerably further west, flowed across the then non-existent Towy 

 Valley at Llandovery, and via the deep Cwm Dwr found its way 

 past the site of the present Brecon. Westwards through the greater 

 length of the Cwm Dwr now flows the obsequent Gwydderig, 

 and eastwards a tributary of the consequent Usk that is gradually 

 diminishing in length. In this neighbourhood there are in progress 

 some very pretty examples of river-capture. Southerly and south- 

 easterly directed tributaries of the Usk are being encroached upon by 

 the growing Gwydderig, and abrupt elbows of capture are seen com- 

 parable with those observable in the Stroud area, where the obsequent 

 Frome, developed from the Severn, has captured such original south- 

 easterly directed tributary-streams of the Thames as that which flows 

 down the Edgeworth Valley. 



The way in which the comparatively broad valeland around Cilmery 

 has originated through the development of the subsequents Irfon and 

 Ithon may possibly suggest an explanation for the somewhat broad 

 valeland expanse around Churchdown, Cheltenham, and Tewkesbury, 

 and its contraction to the south towards Berkeley. When the Towy 

 has overcome the intervening undulating ground in the neighbourhood 

 of Cefn Llwydlo it will make comparatively rapid development, for it 

 will capture the head- waters of the Irfon and invade the ready- 

 excavated valley of Llangamarch. At first, as in the Lower Severn 

 Valley near Berkeley Road Junction, the Towy Valley will be 



