﻿PLIOCENE 
  PEKIOD 
  IN 
  EXGLAXD. 
  711 
  

  

  eastern 
  end 
  of 
  fig. 
  XXI. 
  and 
  in 
  fig. 
  XXIX. 
  The 
  valley 
  of 
  the 
  Mar- 
  

   dyke, 
  however, 
  both 
  where 
  it 
  cuts 
  sharply 
  through 
  the 
  gravel/ 
  as 
  

   well 
  as 
  where 
  it 
  spreads 
  out 
  to 
  form 
  the 
  flat 
  ground 
  below 
  the 
  gravel 
  

   escarpment 
  crossed 
  by 
  fig. 
  XXIX., 
  is 
  destitute 
  of 
  gravel, 
  saud, 
  and 
  

   brickearth, 
  though 
  it 
  is 
  below 
  the 
  level 
  reached 
  by 
  g, 
  and 
  all 
  this 
  

   gravel 
  escarpment 
  drains 
  to 
  it. 
  

  

  From 
  Fobbing 
  eastward, 
  as 
  far 
  as 
  Southend, 
  a 
  space 
  of 
  ten 
  miles 
  

   on 
  the 
  north 
  side 
  of 
  the 
  river 
  is 
  entirely 
  destitute 
  of 
  /, 
  0, 
  and 
  y, 
  alike 
  

   down 
  to 
  the 
  river-bed, 
  neither 
  brickearth 
  nor 
  gravel, 
  save 
  the 
  small 
  

   patch 
  of 
  c 
  at 
  Hadleigh 
  Common, 
  in 
  fig. 
  XXX., 
  occurring 
  there 
  ; 
  and 
  

   this 
  denuded 
  space 
  is 
  continued 
  north 
  over 
  the 
  water-parting 
  between 
  

   the 
  Thames 
  and 
  Crouch, 
  the 
  valley 
  of 
  which 
  last-mentioned 
  river, 
  

   like 
  that 
  of 
  the 
  Mardyke, 
  is 
  destitute 
  of 
  gravel, 
  though 
  the 
  small 
  

   patch 
  of 
  gravel/, 
  shown 
  in 
  fig. 
  YL, 
  at 
  Dunton 
  TTaylet, 
  on 
  the 
  part- 
  

   ing 
  between 
  the 
  Mardyke 
  and 
  Crouch 
  drainage, 
  shows 
  that 
  both 
  

   these 
  valleys 
  have 
  been 
  excavated 
  out 
  of 
  a 
  wide-spread 
  continuation 
  

   of 
  the 
  sheet 
  of 
  /, 
  of 
  which 
  the 
  scarped 
  portion 
  is 
  only 
  the 
  remnant. 
  

   See 
  figs. 
  VI., 
  XXX., 
  and 
  XXXI. 
  

  

  Over 
  the 
  area 
  corresponding 
  to 
  this 
  on 
  the 
  south 
  side 
  of 
  the 
  

   Thames, 
  from 
  Swanscomb 
  to 
  the 
  water-parting 
  between 
  the 
  Thames 
  

   and 
  Medway, 
  in 
  Sheet 
  1 
  , 
  which 
  is 
  formed 
  by 
  the 
  range 
  of 
  London- 
  

   Clay 
  hills 
  on 
  which 
  High 
  Halstow 
  (in 
  figs. 
  XXXI. 
  and 
  XXXII.) 
  

   stands, 
  there 
  is 
  a 
  similar 
  absence 
  ; 
  a 
  patch 
  of 
  <p 
  at 
  Gravesend, 
  a 
  trace 
  

   of 
  it 
  at 
  Higham 
  Station, 
  and 
  a 
  patch 
  of 
  gravel 
  at 
  the 
  Marsh-edgo, 
  

   one 
  mile 
  west 
  of 
  Higham, 
  being 
  all 
  that 
  I 
  could 
  find 
  in 
  this 
  part. 
  

   The 
  other 
  side 
  of 
  this 
  parting, 
  which 
  slopes 
  from 
  High 
  Halstow 
  to 
  

   the 
  Medway, 
  is, 
  on 
  the 
  contrary, 
  gravel- 
  covered 
  over 
  its 
  lower 
  and 
  

   medium 
  elevations, 
  as 
  is 
  the 
  rest 
  of 
  the 
  western 
  side 
  of 
  the 
  Medway 
  

   valley 
  in 
  Sheet 
  1 
  : 
  and 
  this 
  gravel-covered 
  slope 
  is 
  continued 
  across 
  

   the 
  Thames-mouth 
  and 
  along 
  the 
  east 
  side 
  of 
  Essex 
  to 
  the 
  Mack- 
  

   water 
  estuary, 
  where 
  it 
  terminates 
  in 
  a 
  point 
  which 
  bounds 
  the 
  

   denuded 
  space 
  which 
  I 
  have 
  described 
  as 
  stretching 
  from 
  that 
  estuary 
  

   across 
  Sheet 
  1. 
  The 
  gravel 
  slope 
  of 
  East 
  Essex, 
  thus 
  continuing 
  the 
  

   Medway-gravel 
  slope, 
  is 
  crossed 
  by 
  fig. 
  XLL, 
  which 
  traverses 
  also 
  

   the 
  inidenuded 
  north 
  and 
  the 
  denuded 
  south 
  sides 
  of 
  the 
  Blackwater 
  

   estuary 
  valley, 
  and 
  should 
  in 
  that 
  connexion 
  be 
  compared 
  with 
  fig. 
  

   XL., 
  which, 
  crossing 
  that 
  valley 
  to 
  the 
  west 
  of 
  the 
  denuded 
  space, 
  

   shows 
  both 
  sides 
  of 
  it 
  completely 
  sheeted 
  with 
  gravel 
  from 
  />' 
  at 
  

   3GQ 
  feet 
  at 
  Banbury 
  nearly 
  to 
  the 
  sea-level. 
  It 
  seems 
  obvious 
  to 
  me 
  

   that 
  all 
  this 
  denuded 
  space 
  must 
  have 
  been 
  selectively 
  subjected 
  to 
  

   disturbance, 
  while 
  covered 
  with 
  water 
  of 
  some 
  kind 
  that, 
  in 
  con- 
  

   sequence 
  of 
  such 
  disturbance, 
  denuded 
  it. 
  

  

  The 
  Lea 
  valley, 
  also, 
  from 
  Chingford 
  to 
  Broxbourne, 
  i. 
  e. 
  throughout 
  

   nearly 
  all 
  the 
  northern 
  half 
  of 
  Sheet 
  1, 
  is, 
  on 
  the 
  east 
  side, 
  destitute 
  

   of 
  gravel 
  or 
  brickearth 
  down 
  to 
  the 
  Marsh-edge 
  ; 
  while 
  on 
  the 
  west 
  

   side 
  it 
  is 
  sheeted 
  with 
  gravel 
  from 
  the 
  Marsh 
  up 
  to 
  elevations 
  which, 
  

   northwards, 
  exceed 
  150 
  feet 
  (see 
  Map 
  3 
  and 
  fig. 
  XXXIX.). 
  A 
  

   comparison 
  of 
  these 
  features 
  of 
  denudation 
  with 
  thoso 
  shown 
  in 
  

   Mr. 
  Codrington's 
  map 
  of 
  the 
  South-Hants 
  gravel-area 
  indicates 
  to 
  

   my 
  mind 
  that 
  a 
  similar 
  selective 
  denudation 
  has 
  taken 
  place 
  there. 
  

  

  