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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 drainage 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 escarpment and through its breaches. 

 The valley of Shipston on Stour, which is described as a species of 

 bay in the escarpment of the Cotteswolds, 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 re- 

 peatedly 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 of Oxford the progress of the river is op- 

 posed 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 eestuary of the Wash. 



The author inquires how this configuration of the valleys could 

 have been produced on the fluviaiist'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, however, another alterna- 

 tive 5 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 

 channels) into the present valleys. The author calculates the mass 

 of materials which must on this supposition have been excavated and 

 washed away, and contends that the drainage of atmospherical waters 

 along such an inclined plane (which would have a fall of 1 feet per 

 mile) does not afford an agent adequate to such vast operations. 



The Oxford chain has suffered greatly from denudation, being 

 broken into several detached groups. 



Among these, some insulated summits are capped by patches of 

 gravel, partly derived from transition rocks, partly from the chalk 

 formation. These prove the extent to which denudation must have 

 proceeded since they were lodged in their present situation; as they 

 must have been transported from their native habitats along uni- 

 formly inclined planes, which have subsequently been excavated. 

 III. Issuing from the defile of the Oxford chain, the river flows 



