Wood— Structure of Valleys in Essex. 353 



Noio the entire area of this great re-excavated and remodelled trough is 

 totally destitute of gravel. All the other river valleys of East Anglia 

 contain, upon their edges and in their troughs, beds of gravel, not in 

 any way resembling the great sheets of the Thames and East Essex 

 gravels, but dispersed in small patches, and ansvii-ering in position to 

 the series I have described in the former paper as a; 2 and x 3. Even 

 the xindulating London Clay country, intervening between the south- 

 western termination of the Crouch Valley and the edge of the Thames 

 gravel, contains many very small and shallow patches of gravel 

 belonging to one or other of those series ; but in the two valleys under 

 discussion there is a total absence of anything, however small in 

 dimensions, that approaches to the character of a gravel patch — a 

 feature which, in my experience, is unparalleled in any other valley 

 of the east of England.^ Now when we come to consider the relation 

 which the East Essex gravel (through which the valleys under dis- 

 cussion cut at right angles) bears to the denudation of the great 

 valley of the Weald, and the evidence which the position of the 

 gravel beds in the latter convey of a great reversal of the drainage 

 haviag taken place at a very late date, and when we reflect on the 

 extremely late date at which I have endeavoured in the former paper 

 to show how the Thames river, with its North Sea outlet, came into 

 existence, and how, in all respects, this North Sea outlet of the 

 Thames coincides in structure with that of the Crouch, we find a con- 

 currence of evidence which points to the cause of the redenudation I 

 have been describing, and of the formation of the mouths of the 

 Thames and Crouch, having been the disturbances that gave rise to the 

 reversal of the Wealden drainage, to which I have presently to allude ; 

 evidence which points also to the period of this event belonging to 

 that very modern time when the subarctic conditions, to which the 

 formation of gravels has been due, had passed away, and marsh mud 

 become the sedimentary result of the occupation of the valleys by 

 water. 



The following Sections will assist the apprehension of the structure 

 I have been endeavouring to describe. (See Sections 10, 11, 12, and 

 13, beside Map) :■ — 



Section 12, like Section 9, traverses the line of dislocation marked 

 by the estuary of the Blackwater and river Chelmer, to the south 

 of which the block of country lying between this estuary and river 

 on the one side, and the Thames mouth on the other, has, more or 

 less, been detached and elevated. The same apparently inconsistent 

 relative positions of the Middle Drift and East Essex gravel present 

 themselves as a consequence in this section as they do in Section 9. 

 This apparent inconsistency not only disappears when the explana- 

 tion of subsequent disturbances is applied to it, but the feature 

 itself falls into unison with the many other surrounding features 



^ Except that of tlie Hamford Water surrounding the Naze point of Walton, 

 which has participated iu the same re-excavation and redenudation as the valleys of 

 the Crouch and Blackwater Estuary, and like them, has on the crown of the slopes 

 forming its valley, patches of denudation gravel, analogous to those described in the 

 former paper under the symbol x 2. 



VOL. III. — NO. XXVI. 23 



