106 Wood— Structure of the Thames Valley. 



of admitting the North Sea, had, like that which threw down the 

 forest, and, by its interception of drainage, originated the peat, 

 probably begun in the convulsions mentioned in conclusion 4. 



6. That, while we have no set of terrace -gravels marking the 

 present valley, the condition of the northern slope east of London 

 does point to the formation of the original valley in a manner bearing 

 some analogy to terrace formation ; but the corresponding part of 

 the southern slope of the original valley having, with the exception 

 of the solitary remnant of Shooters' Hill, been destroyed,^ there now 

 remains nothing resembling such a terrace condition as the valleys 

 of the Somme and the Seine are represented to possess. 



These are all the conclusions which the sections and facts sub- 

 mitted here justify ; but, could the whole phenomena relating to the 

 denudation of the drift, and to the formation of the Post-glacial 

 gravels in those counties lying south of Flamborough Head, which 

 are occupied by formations newer than the Trias, be presented to 

 the reader, it could, I think, be made to appear that the water 

 depositing the Thames gravel was that of a strait connecting the Post- 

 glacial sea of the west, beyond Eeading, with the same sea over the 

 Weald, which was then denuding the Wealden . area prior to the 

 excavation of the Weald Valley between its Chalk escarpments ; - and 



' It would incumber the paper to show why, since the original valley was cut 

 through the drift, no outlier of di-ift should occur on the top of Shooters' Hill, 

 corresponding to that on Havering Hill; but it is capable of a very clear and 

 interesting explanation. To give it, however, would require a description of the 

 position which the Upper and Middle-drift occupies in Essex, Middlesex, and 

 elsewhere. 



2 To make this view intelligible, it is perhaps necessary to explain that I regard the 

 gravel of Southend (which, separated from the Thames gravel by several miles of 

 gravel -less country, extends in the form of a narrow strip behind the marshes 

 bordering the North Sea for nearly 20 miles in a NN.E, direction along the coast 

 of Essex, and is capped in places by Upper Brickearth, and which, although it is the 

 same as that fringing the estuary of the Medway between Rochester and the Nore, I 

 will distinguish as the " East Essex gravel") as a remnant of a great sheet 

 of gravel that was deposited in an estuary whose mouth joined (near Rochester) the 

 sea, then extending over the "Wealden area prior to the excavation of the Weald 

 Valley. This estuary, starting from the point where its mouth, inosculated with that of 

 the Thames gravel channel, south-west of Rochester, extended in a NN-E. direction 

 through what is now the mouth of the Medway, and traversed a land-tract, of which the 

 greater part occupied the area now represented by the mouth of the Thames, and by that 

 part of the North Sea which is known as the Swin, such tract having been submerged 

 by the convulsions giving rise to Sea Reach. The mouth of this estuary discharged into 

 the eea over the Weald, in contiguity to the south-eastern mouth of the channel of the 

 Thames gravel, the subsequent elevation of the Weald and submergence of the North 

 Sea having reversed the direction of the drainage through the valley of the Medway, 

 so that it now flows northwards into the North Sea, instead of southwards, as it did 

 during the Thames gravel period, and for several stages subsequent to that period, 

 into the Weald. To show the grounds for this view, however, it would be necessary 

 to describe the condition of the valleys of the Aide, Deben, Orwell, and Stour, and 

 especially the condition and structure of the valleys of the Blackwater and Crouch. 

 It must be obvious, however, that if the Thames gravel were the deposit of the 

 present valley at a time when the country generally stood at a lower level (whether 

 accompanied by floods or not), then, not only sliould that gravel extend to the 

 Thames *nouth, but these six valleys, which open, like that of the River Thames, into 

 the North Sea, and are all, in some part of them, cut either through the Boulder-clay, 

 orelse the Middle Drift, should, like the Thames valley, contain a sheet of gravel similar 



