1899] THE DEVELOPMENT OF RIVERS 287 



river when it had lost all its western branch, and only received the 

 drainage down its northern valley. In turn its northern branch was 

 beheaded, and its drainage-area further and further diminished by the 

 growth of the obsequent Isborne. So the river is reduced to its present 

 small volume — a little wriggling brook. 



Having stood on the Chiltern Hills overlooking the Goring gorge 

 and noted the details of that scene, it is not difficult, when subsequently 

 viewing the Cotteswold escarpment and the old West Coin breach 

 from the south end of the Cleeve Hill plateau, to transfer the details 

 of the former scene to the latter, and imagine the aspect of the Cottes- 

 wold uplands and river-system when its stage of development was the 

 same as now belongs to the Chalk escarpment. That is the picture of 

 what the original Coin river-system — the river which cut the big- 

 meanders — must have looked like before its capture by the Severn. 

 Between Cleeve and Leckhampton Hills there was a broad river-valley 

 perhaps some 250 feet deep. In that valley a river quite as big as 

 the present Thames at Goring ; and stretching away to the west, right 

 to the Malverns, there was a broad plain of Lias about 250 feet below 

 the Cotteswold escarpment. The Upper Lias corresponded to the Green- 

 sand series, and the Lower Lias to the Oxford Clay of the Oxford 

 district. And across this plain ran the original Coin, much in the same 

 way as the Thames now crosses the Oxford Clay before entering the 

 Chalk Hills ; also in this plain there had been developed subsequent 

 streams corresponding in all respects with the Ock and Thame. The 

 stage of river-development now to be seen in the neighbourhood of the 

 Goring gorge was once the stage of river-development appertaining to 

 the gorge which now lies west of Cheltenham. Here this stage of 

 development passed into a new phase by the successful working back 

 of the river Severn. 



After what may be called this Severn victory in the Vale of 

 Gloucester, the further development of the river-system may be shortly 

 told. It started or strengthened two subsequent branches — one north- 

 wards which captured the Shropshire and Welsh drainage, the other north- 

 eastward — the present Warwick Avon 1 which cut off the head-waters 

 of the Thames tributaries from the north ; and has developed obsequent 

 branches like the Isborne and the Stour to further shorten the Thames 

 system. While the Thames was thus suffering from the successful 

 growth of the Severn, it had also experienced considerable loss from 

 other rivers. In the north-west its head-waters had been taken by the 

 Dee, Weaver, Mersey, etc. In the north it had suffered from the 

 Trent, as well as from the three parallel subsequents, the Welland, 

 Nen, and Bedford Ouse. From the latter it had suffered very con- 

 siderably, especially in regard to tributaries which enter near London. 



1 From the lie of the ground south of Tewkesbury it seems reasonable to conclude that 

 the Avon formerly joined the Severn a few miles south of Tewkesbury, and that the present 

 junction at Tewkesbury is a comparatively recent development. 



