1867.] WOOD SOUTH-EAST OF ENGLAND. 405 



out to the sea, represented by the Chalk country, and also where the 

 East Essex gravel opens to it, the gravel is denuded from a lofty 

 brow in the direction of the Chalk country, as I will show. One other 

 channel (which not improbably may have been connected with that 

 of the East Essex gravel through the area between Kent and Essex 

 now occupied by the IN'orth Sea) occupied the London Clay and Lower 

 Tertiary country lying north and east of Canterbury, opening to 

 the sea over the Chalk country of Kent about this place. Of the 

 deposits of these three channels, the Western or Thames channel, and 

 the Eastern or Canterbury channel, have been the most broken up 

 and denuded ; the intermediate channel of the East Essex gravel 

 has been but little disturbed except at its embouchure, where the 

 gravel is cut down some 150 feet to the Chalk country. It would oc- 

 cupy too much space to show in any detail the mode in which this has 

 taken place ; but that of the break-up of the Thames sheet in 

 the channel-mouth, between Dartford Heath and the East Essex 

 dividing ridge, will be found to be copiously illustrated by sections 

 in the memoir ; and sections illustrative of the break-up and terrace- 

 creation in the other channel- openings are given there also. I will 

 therefore confine myself here to three simple sections in illustration 

 of the structure at the channel-openings. 



The first section, fig. 10, gives the denudation at the opening of 

 the Thames gravel channel around Eichmond and Wimbledon. In 

 this section we have the gravel very sharply denuded towards the 

 Chalk country, the Tertiary beds and the Chalk towards the Wealden 

 area coming up with a considerable dip, which increases as the Chalk 

 country is approached. This dip (of course immensely exaggerated 

 in the compass of the section) indicates the sharp nature of the 

 Wealden upthrow, which succeeded the denudation of the gravel, but 

 which was preceded, as I have to show, by an intermediate period 

 occupied by the formation, in the broken- up beds of the channel- 

 troughs, of a series of fluviatile openings in which accumulated the 

 gravels and brick-earths of the lower terraces, grouped in the sur- 

 veyed sheets under the symbols x5 and ^ 5'. By varying the line of 

 section a little, and carrying it from Wimbledon Hill to Croydon, 

 we should see the denuded Tertiary beds that lie below the brow of 

 gravel exactly in the same position as in fig. 10, but overspread 

 by the flat sheet of the Wandle gravel, which, as shown on the 

 Geological Survey Sheet N"o. 8, expands from the Thames towards 

 the Chalk country like a broad river, terminating abruptly, as the 

 chalk comes up, with a square end against that formation. This 

 represents one of the fluviatile outlets into which the channel- 

 openings shrank as the sea receded towards the Weald. In the 

 neighbourhood of the section, however, we find no trace of any 

 other gravel than that on the brow, and may therefore infer that 

 the denudation exhibited by it represents simply the recession of 

 the sea towards the Weald. This shows the London clay denuded 

 with the gravel, consistently with the position assumed at the com- 

 mencement of this paper — namely, that the upthrow and denudation 

 of the Weald followed the deposition of the Thames gravel, which had 



