Geological Society » 379 



tuting the rivers Isis, Churn, Colne, Lech, Windrush, Evenlode, and 

 Cherwell ; this chain of hills being entirely broken through by the Colne, 

 Evenlode, and Cherwell, which rise from sources in the lias plains beyond 

 its escarpment. The height of most of these sources is calculated at about 

 400 ft. above the sea. 



Each of these valleys is separately described, and the general features 

 of denudation presented by the Cotteswold chain are pointed out ; these, 

 it is asserted, bear traces of the most violent action, and they are con- 

 trasted with the state of repose which has evidently prevailed in the same 

 districts from the period to which our earliest historical monuments ascend. 

 In the most exposed situations, and those which appear to have suffered 

 most from the action of the denuding causes, earth works of British and 

 Roman antiquity are frequently found, attesting by their perfect preserva- 

 tion that the form of the surface has remained unaltered since the time of 

 their construction. The drainage of the atmospherical waters has here 

 produced no sensible effect for more than fifteen centuries : it is inferred, 

 therefore, that to assign to this cause the excavation of the adjoining 

 valleys, 600 or 700 ft. deep, is to ascribe to it an agency for which we have 

 no evidence; the evidence, indeed, as far as it can be examined, being 

 adverse. 



The disposition of the water-worn debris, drifted against the Cotteswold 

 chain and through the breaches opened in it, is also examined ; and much 

 of it is shown to be derived from rocks situated to the north of the valley 

 of the Warwickshire Avon, and to be completely cut off by that valley 

 from the Cotteswold district. It is contended that pebbles of this origin 

 can never have been transported by the actual streams, because the drain- 

 age of these streams is, and always must have been, from the escarpment 

 of the Cotteswolds to the valley of Avon; whereas the course of the 

 pebbles is directly opposite, viz. across the Avon, and thence to that escarp- 

 ment and through its breaches. The valley of Shipston on Stour, which 

 is described as a species of bay in the escarpment of the Cotteswold, is stated 

 to contain the most remarkable instance of this disposition. 



II. The river collected from these head waters flows through the plain of 

 Oxford, which is covered to a great extent by water-worn debris ; these are 

 diffused over situations inaccessible to the present floods, and, if produced 

 by the actual streams, we must suppose that they have repeatedly changed 

 their channel, so as to have flowed successively over every portion of the 

 plain where these debris are now found ; the oldest historical monuments 

 attest, however, the permanence of the actual channels, and the floods at 

 present bring down no pebbles whatsoever. 



On the south of the plain at Oxford, the progress of the river is opposed 

 by a chain of hills, called by the author the Oxford chain. This is passed 

 by a defile broken through it. Were that defile closed, an extensive lake 

 would be formed above Oxford, and the waters would be turned into the 

 valley of the Ouse ; by which they would empty themselves into the estuary 

 of the Wash. 



The author enquires how this configuration of the valleys could have been 

 produced on the fluvialist's theory. He argues, that if the Oxford chain 

 originally (as at present) formed a barrier of superior elevation to the tract 

 intervening between itself and the Cotteswolds, that barrier must have turned 

 all the drainage of the Cotteswolds into the vale of Ouse. Under those 

 circumstances, the crest of the Oxford chain could never have been eroded 

 by waters which would have flowed off in another direction. There is, how- 

 ever, another alternative ; and the interval between these chains may be 

 supposed to have formed originally a uniformly inclined plane, from the 

 summits of the one to those of the other, along which the waters once 

 flowed, and which they have since furrowed (by perpetually deepening their 



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