Wood— Structure of the Thames Valley. 



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contemporaneous with, the Thames gravel, 

 is manifestly no part of the once continuous 

 and persistent sheet which filled so large a 

 proportion of the original valley of the 

 Thames, and which, on the north side of 

 the river, still remains in a continuous sheet. 

 This gravel (much of which is capped by 

 brickearth) extends only a little way west 

 of Southend, although it rims northwards 

 along the coast for nearly 20 miles, in a 

 strip varying from 2 to 5 miles in breadth. 

 So also on the south side there is an interval 

 of several miles wholly destitute of gravel 

 in any form, extending eastwards from 

 Higham to High Halstow ; but east of the 

 latter place a gravel sets in, which is found 

 at several places between it and the Med- 

 way; and which, although, like the South- 

 end gravel, it probably is coeval with, the 

 Thames gravel, is also manifestly no part of 

 that formation itself. On both sides of the 

 Thames, therefore, we have the Thames 

 gravel [x i/') entirely cut off from the sea, 

 into which tlae Thames river discharges, by 

 a breadth of several miles of land ; and 

 Section 5, drawn across the entire valley 

 forming the mouth of the Thames, and 

 directly transverse to the course of the 

 Thames river east of the boundary of the 

 gravel {x4/'), shows both the absence of 

 the gravel and the mode in which (long 

 subsequent to the gravel and brickearths) 

 the river has been opened through this 

 gravel-less area to the sea. It also shows 

 distinctly the cutting down of the valley "^ 

 on the north side of the river from the § 

 Upper Drift or Boulder-clay (which at this S o g 

 part overlaps the Middle Drift gravel by so §1 

 several miles). This north slope, it is to g| 

 h& borne in mind, is a part of the original 5=3 

 valley beyond the limit to which the g^ 

 Thames gravel {x ^") reaches ; on the p •£ 

 other hand, the slope forming the south 

 side of the valley through which the river 

 Thames runs has been materially modified o | 

 by the causes which brought Sea Eeach into _ t. " 

 existence, and does not, in its present form, fe: z| 

 represent any portion of the original Thames ^§iB 

 Valley. The fault which at Sea Eeacb te^*« 

 opened the Thames river to the sea indicates a 

 three and four hundred feet. 



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