20 PKOCEEDINGS OP THE GEOLOGICA.L SOCIETY. [NoV. 9, 



3rd. The difficulty of reconciling the presence of Tertiary pebbles 

 in certain "Wealden gravels with an origin by means of rivers flowing 

 in the direction of the present ones, however high we imagine those 

 rivers to have been. 



4th. The antagonism between the character and form of the 

 major vaUey of the Weald and that of any conceivable excavation 

 which could result from the agency of rivers, not merely from rivers 

 coincident with the present ones in direction, but from any rivers 

 at all. 



5th. The proof which the position of the gravels of the Thames, 

 of East Essex, and of the Canterbury heights, and especially the po- 

 sition of the lofty ridge dividing the Thames and East-Essex gravels 

 from each other, furnishes that the sea of this gravel-period was to 

 the south of these gravel-sheets. 



6th. The circumstance that the old coast-contour, when the sea 

 lay within the Weald, and the channels and river-drainage entered 

 it from the north, remains now stamped, as from a die, on the Chalk 

 and Lower-Greensand escarpments, except in the particular region 

 where that on the chalk was obliterated by the excessive marine 

 denudation consequent upon the acute upthrow of the Guildford 

 Hogsback — especially the dry inlet mouth at Merstham. 



7th. The natural manner in which the gravels with Tertiary 

 pebbles, mentioned in proposition no. 8, fall into their places, if they 

 be regarded as having received these pebbles by means of channels and 

 rivers from the north ; and the sufficient explanation which a tidal 

 indraught from the south, when the shore-hne was chalk, and the 

 principal denudation of the subcretaceous strata not yet accomplished, 

 oifers for the small quantity of subcretaceous material and enormous 

 quantity of flint possessed by the Thames, East-Essex, and Canter- 

 bury-heights gravels. 



8th. The existence of a cause, in the shape of an isthmus at 

 Dover, which was adequate to induce a tidal scour sufficient, with the 

 river-flow from the north, to produce a denudation of the form and 

 character which the major valley and the minor valleys together 

 present ; the equally adequate cause for a cessation of this denuda- 

 tion, and for the mastery so attained by the elevatory action over 

 the denudation, which the opening of the Dover Straits (generally 

 admitted to be of a late Postglacial date) furnishes ; also the general 

 fitting in of all these propositions with one another, and with the 

 features presented, on the one hand, by the very recent opening of 

 the mouths of the Thames and Crouch through the great ridge, and 

 the absence from the valleys of the Thames mouth and of the Crouch 

 river of either gravel or brickearth ; and, on the other hand, by the 

 character of the Selsey deposits. 



Note eocplanatory of the Map (PI. I.). 



In order that the physical features may appear, the Atherfield- 

 clay has been shaded in with the Weald-clay, instead of, as usually, 

 with the Lower Greensand. 



The lines A and B indicate those of the two sections, A and B, which 



