1867.] WOOD — SOUTH-EAST OF ENGLAND. 39^ 



Upper Glacial sea -bed, the detached portions, or outliers, of the 

 deposit of that sea which occur on the west of the Lea valley 

 having, at that time, formed islands detached from the mainland, — 

 represented by the main mass of the upraised sea-bed. As the 

 emergence and denudation proceeded, these islands became, with 

 the outliers of the Bagshot Sand at Hampstead and Harrow (this 

 sand, by reason of the structure shown in figs. 1-3, forming a 

 common deposit with the Glacial clay for the first action of the 

 denudation), the eminences of land up which stretched an inlet from 

 the main sea that was afterwards occupied by the Thames gravel. 

 We have, therefore, on the east of London, so far as this part of the 

 structure extends, the simple case of an early Postglacial sea- 

 margin, with the land breaking off into detached islands represented 

 by outliers of the Glacial beds ; and this feature becomes readily 

 appreciable by the eye when the delineation of the Glacial beds in the 

 Index Map accompanying the memoir is examined. 



Precisely similar features are exhibited by the delineation of the 

 south-western extremity of the Glacial beds in the counties of Buck- 

 ingham and Northampton ; and, in order to collate the features of 

 this part with those exhibited in Essex, I annex a section drawn 

 from the lip of the Glacial beds near Buckingham to the valley of 

 the Cherwell* (fig. 6). . 



Here we have the denudation, which in this direction cuts off the 

 Glacial beds, descending through successive deposits of Oolite and 

 Lias, which rise up (like the Chalk and Lower Cretaceous beds in fig. 

 4) as the denudation descends through them. If a local geological 

 map of this neighbourhood, given in the memoir, be examined, it is 

 apparent that the denudation, which in fig. 6 is shown across the 

 plateau-country, commenced in the Upper Glacial clay and descended 

 westward along the valley of the Ouse to that of the Cherwell, form- 

 ing both those valleys by the gradual westerly recession of the sea. 

 The troughs through which the rivers Ouse and Cherwell run in 

 these parts both expand, from the westerly direction of the denuda- 

 tion, in the opposite direction to the present course of those rivers, 

 and are beautifuUy defined by the map-colours of the formations 

 (from the Glacial beds to the Lower Lias) which have been exposed 

 in their turn by the denudation in its descent. So entirely inde- 

 pendent of the denudation of these troughs are the rivers which 

 traverse them, that, in the case of the one now partly occupied by 

 the upper waters of the Ouse, although its denudation is uniformly 

 in a western direction, the present drainage through it runs in two 

 contrary directions — one part east into the Ouse, and the other in 

 the direction of the denudation. This latter part, however, by falling 

 into the Cherwell eventually, like the rest of the drainage originating 



* The Section of the valley at Buckingham, given in the Memoir of the Geo- 

 logical Survey in explanation of Sheet 45, appears to me to be quite at variance 

 with the actual structure of it. So far from there being any evidence of the 

 existence of an actual valley in this part prior to the Glacial period, the mode 

 in which the valley of the Ouse is cut through the Glacial beds shows the valley 

 to have been wholly formed since the deposition of the Glacial clay, . - 



