in. THE RAY. THE THAMES NEAR OXFORD. 39 



right toward this gap in the hills, and in some pre-glacial sera may 

 have been continued into it across what is now the Thames Valley k . 

 At some earlier time, the discharge may have been still further 

 west, through the broad depression which reaches from near Fifield 

 to Marcham and Abingdon; a depression from which the Kim- 

 meridge clay has been wholly swept away. Indeed it is almost 

 necessary to suppose such a current in a comparatively late geo- 

 logical period, for how else is the enormous accumulation of cal- 

 careous gravel stretching westward from Abingdon to be accounted 

 for ? Other openings more or less complete across the ' middle 

 ridge ' occur on the course of the Cole, between High worth and 

 Faringdon, and of the Key north of Swindon, both streams running 

 through the ridge to the northward. 



The most probable general view appears to represent the vale 

 of the Thames above Iffley as a great water ramified among hills, 

 at a level higher than any of the stratified gravels now dry in the 

 vale 1 , and that water of similar character occupied the low ground 

 above the contracted part of the river course at Clifton and Dor- 

 chester, spreading westward toward the Vale of White Horse, and 

 eastward toward the Vale of Aylesbury. From the boundary hills 

 on all sides the streams, descending with force for very long periods 

 of time, transported the loose detritus, and deposited it abundantly 

 near to their embouchures. Not exclusively, however; because 

 in such lakes as have been supposed the wind-force would create 

 much disturbance, and, in some places, shift the gravel into long 

 continuous banks. 



The broad plain of Ottmoor would become a lake, if the narrow 

 part of the valley of the Kay at Islip were to be effectually barred 

 by the crossing of the rocks, as once, no doubt, it was. Still, from 

 time to time Ottmoor is heavily flooded, and heedless pedestrians 

 may have to try the depth of the water, as happened to myself 

 a few years ago in crossing toward Studley. 



That a lake once existed here is likely, but that the present broad 

 surface is its dried bed, is not a safe supposition. The river may 

 have flowed through a contracted lake in the midst of a wider 



k The gravel beds of Botley and North Hincksey may have been brought by it. 



1 The gravel at Oxford is nowhere more than thirty feet above the valley, but it 

 rises to a greater elevation about one and a half miles to the northward, and pre- 

 serves this elevation to Yarnton. 



