100 Wood — Structure of the Thames Valley. 



on the northern side, at a point thirteen miles west of Shoeburyness ; ^ 

 while, on the southern side, its limit is Higham, twelve miles west of 

 Sheerness and Shoeburyness, where a most remarkable and isolated 

 fragment of the deposit remains, having been saved by a fault, 

 which threw it down, with the London clay on which it rested, into 

 the midst of the Chalk which now forms the surrounding country. 

 This detached fragTaent occurs, too, several miles east of any other 

 portion of Thames gravel now existing on the southern side of the 

 Thames. Beyond these points, not a vestige of the Thames gravel, or of 

 any other, appears for many miles. On the northern shore, at Hadleigh 

 Common, on the top of a hill, and at a distance of eight miles to the 

 eastward of the point of absolute stoppage of the formation, we meet 

 the first signs of gravel in the form of a small patch that does not 

 correspond with the Thames gravel (aj4''), but does so with the 

 denudation gTavel (x 2) ; while to the north of Hadleigh, at a 

 distance of a mile, there is about a square mile of summit gravel (xl) 

 at Daw's Heath and Great Wood. Two miles east of this, and at a 

 distance of ten miles from the easternmost edge of the Thames 

 gravel (a; 4'^), another gravel sets in, which, although it may be 



' As the Ordnance Sheet, No. 1, which comprises the entire valley of the Thames, 

 from London to the sea, has not yet been mapped by the Geological Survey, I subjoin 

 the eastern and northern boundary of the Thames gravel through it : all the names 

 of places being those on the Ordnance sheet. Starting from a point about midway 

 between Cheshunt and Broxbourne, the eastern boundary of the Thames gravel 

 follows the course of the Lea on its eastern side very closely, and at a distance varying 

 from a furlong to one mile from that stream itself as far as Walthamstow, at which 

 place it turns abruptly to the eas:, and passing through Forestside, bends for two 

 miles up the Roding valley, for a mile above Woodford Bridge, whence it descends 

 due south for an equal distance ; then, turning round Clay Hall, it stretches 

 E.N.E. to Fairlop plain. Then sweeping S.E., the boundary curves round Lawn 

 Farm at a distance of six furlongs on the west and south sides of it, and bending 

 E.N.E. again to (the northernmost) Collier Eow, it curves fi-om that place southwards 

 passing through " Priests," eastwards, but with a slight northerly curve, to Hare 

 Hall. It crosses the railway at Hare Lodge to New Eeadingcourt ; then, turning 

 abruptly, it runs S. by E , to Upminster Bridge, whence it stretches E.S.E. to (Orsett) 

 Fengate, passing in its course, and immediately south of them, the villages of 

 Upminster, Cranham, and North Ockendon. It then bends close round the north 

 side of Orsett to Rotten Eow, whence it turns north to Horudon-on-the-Hill, which 

 it touches on the south side, then trending east, it crosses the Vange Eoad half a mile 

 N.E of Stanford-le-Hope ; then bending N.E. for a mile it curves again, and crossing 

 the road from Corringham to Laindon, six furlongs "W.N.W. of Corringham, passes to 

 Fobbing, crossing that village one furlong north of the church, when it abruptly 

 bends south, and keeping close to the village, passes in a S. by E. line to the Marsh, 

 a furlong east of P'obbing Wharf, where it stops ; but as it appears at the bottom of 

 the dock there, it is probably continued under Corringham Marsh to the river, a mile 

 west of Thames Haven. This boundary, which I have tested mmutely, will, after 

 quitting the Lea, be found to be almost identical with the line of the Thames Eiver, 

 except in those reaches which have been formed subsequently to the gravel by the 

 faults described in the text, viz.. Sea Eeach, Gravesend Eeach, Erith Rands, and 

 Woolwich Eeach, with the lines of which, however, it shows not the remotest 

 coincidence. The Geological Survey Sheets, Nos. 7 and 8, pui-port to show part 

 of the formation west of London; the gravel of Wimbledon and Eichmond Hills, 

 however, is not included as any part of it; but sheet No. 13, which should contain 

 the westerly extremity, including the great expansion of the formation around 

 •Reading, has been published without any delineation of the greater portion of the 

 formation comprised in it. 



