﻿PLIOCENE 
  PEEIOD 
  IN 
  ENGLAND. 
  703 
  

  

  nothing 
  in 
  bed 
  4 
  in 
  this 
  valley 
  to 
  indicate 
  that 
  the 
  water 
  at 
  the 
  

   time 
  of 
  its 
  accumnlation 
  was 
  fresh, 
  — 
  at 
  any 
  rate 
  perennially 
  fresh 
  ; 
  

   and 
  it 
  is 
  this 
  bed 
  only 
  which 
  from 
  the 
  elevation 
  it 
  attains 
  offers 
  any 
  

   indication 
  of 
  a 
  volume 
  of 
  water 
  having 
  occupied 
  the 
  Thames 
  valley 
  

   very 
  much 
  in 
  excess 
  of 
  that 
  at 
  the 
  present 
  day 
  ; 
  for 
  if 
  we 
  compare 
  

   the 
  height 
  reached 
  by 
  that 
  part 
  of 
  3 
  at 
  Grays 
  which 
  contains 
  shells, 
  

   with 
  the 
  bottom 
  of 
  the 
  Cyrena-TiYei 
  there, 
  shown 
  in 
  figs. 
  XXI. 
  and 
  

   XXII., 
  the 
  probable 
  volume 
  would 
  not 
  exceed 
  that 
  of 
  the 
  present 
  

   river 
  at 
  Northfleet, 
  where, 
  when 
  my 
  father 
  was 
  a 
  sailor, 
  fresh 
  water 
  

   for 
  the 
  China 
  voyage 
  was 
  taken 
  in 
  from 
  the 
  Thames 
  itself 
  ; 
  while 
  

   the 
  flatness 
  of 
  the 
  fall, 
  and 
  the 
  greater 
  distance 
  of 
  the 
  sea-water 
  

   from 
  Grays 
  during 
  the 
  formation 
  of 
  <f> 
  2 
  than 
  it 
  now 
  is 
  from 
  

   Northfleet, 
  which 
  the 
  features 
  of 
  the 
  Clacton 
  section 
  show, 
  seem 
  to 
  

   me 
  to 
  remove 
  all 
  difficulty 
  in 
  this 
  question, 
  so 
  far 
  as 
  beds 
  1, 
  2, 
  and 
  

   the 
  lower 
  part 
  of 
  3, 
  at 
  Grays, 
  Erith, 
  Crayford, 
  and 
  Ilford, 
  are 
  con- 
  

   cerned. 
  As 
  regards 
  4, 
  and 
  the 
  upper 
  part 
  of 
  3, 
  if 
  fluviatile 
  shells 
  

   have 
  occurred 
  in 
  them, 
  the 
  fact 
  has 
  not 
  come 
  to 
  my 
  knowledge, 
  nor 
  

   should 
  I, 
  when 
  the 
  great 
  flooding 
  of 
  the 
  country 
  at 
  that 
  time 
  is 
  

   considered, 
  regard 
  it, 
  if 
  it 
  did, 
  as 
  a 
  difficulty 
  *. 
  The 
  bed 
  

   <p 
  4 
  at 
  Clacton 
  is 
  unfossiliferous 
  ; 
  but 
  from 
  its 
  transgressive 
  

   position, 
  and 
  its 
  evident 
  succession 
  by 
  increasing 
  depression 
  to 
  the 
  

   bed 
  (j) 
  3 
  there, 
  with 
  its 
  marine 
  or 
  estuarine 
  shells 
  (notwithstanding 
  

   that 
  some 
  denudation 
  of 
  the 
  edge 
  of 
  3 
  seems 
  to 
  have 
  occurred 
  

   during 
  this 
  movement), 
  we 
  cannot 
  question 
  its 
  having 
  been 
  due 
  to 
  

   this 
  redepression. 
  The 
  deposit, 
  however, 
  changes 
  from 
  the 
  clay 
  and 
  

   sanely 
  loam 
  of 
  2 
  and 
  3 
  to 
  gravel 
  with 
  which 
  loam 
  is 
  inter- 
  

   mixed 
  ; 
  and 
  this 
  seems 
  to 
  me 
  to 
  conspire, 
  with 
  the 
  form 
  of 
  brick- 
  

   earth 
  with 
  bands 
  of 
  race 
  which 
  p 
  4 
  assumes 
  within 
  the 
  present 
  

   Thames 
  valley, 
  to 
  show 
  that 
  the 
  later 
  part 
  of 
  this 
  depression 
  was 
  

   accompanied 
  by 
  a 
  refrigeration 
  of 
  climate 
  consequent 
  on 
  the 
  approach 
  

   of 
  the 
  minor 
  glaciation 
  described 
  in 
  Stage 
  VII. 
  This 
  approach, 
  as 
  

   well 
  as 
  the 
  wane 
  of 
  that 
  glaciation, 
  seems 
  to 
  have 
  been 
  accompanied 
  

   by 
  great 
  flooding 
  of 
  the 
  land 
  ; 
  for 
  the 
  gravel 
  g, 
  which 
  accumulated 
  

   during 
  that 
  stage, 
  passes 
  up 
  into 
  brickearth 
  in 
  a 
  similar 
  way 
  to 
  

   that 
  in 
  which 
  ^ 
  3 
  of 
  the 
  Oymia-formation 
  does 
  ; 
  and 
  other 
  

   phenomena 
  described 
  in 
  that 
  stage 
  point 
  to 
  this 
  flooding 
  having 
  

   occurred 
  at 
  the 
  close 
  of 
  this 
  glaciation. 
  If 
  this 
  was 
  the 
  case 
  when 
  

   the 
  Ctyrgna-depression 
  was 
  extending 
  the 
  sea- 
  water 
  up 
  the 
  eastern 
  

   valleys, 
  the 
  effect 
  might 
  have 
  been 
  to 
  render 
  that 
  water 
  uninhabi- 
  

   table 
  by 
  mollusca, 
  whether' 
  marine 
  or 
  freshwater. 
  Something 
  

   evidently 
  caused 
  the 
  disappearance 
  of 
  both 
  kinds 
  of 
  mollusca 
  at 
  

   Clacton 
  before 
  bed 
  4 
  accumulated 
  there 
  ; 
  and 
  the 
  mixture 
  of 
  loam 
  

   with 
  the 
  gravel 
  of 
  that 
  bed 
  is 
  suggestive 
  of 
  freshets 
  filling 
  the 
  rivers 
  

   and 
  estuaries 
  with 
  a 
  great 
  quantity 
  of 
  mud, 
  which, 
  in 
  the 
  more 
  sea- 
  

   ward 
  position 
  of 
  Clacton, 
  was 
  intermixed 
  with 
  a 
  large 
  quantity 
  of 
  

   stones 
  by 
  coast-ice 
  from 
  shores 
  formed 
  of 
  gravels 
  c 
  and/, 
  but 
  which, 
  

  

  * 
  Prof. 
  Morris, 
  in 
  a 
  notice 
  of 
  the 
  Grays 
  brick-pits 
  in 
  the 
  Geol. 
  Mag. 
  for 
  1867, 
  

   p. 
  63, 
  speaks 
  of 
  the 
  " 
  brown 
  clay 
  " 
  over 
  the 
  false-bedded 
  sand 
  <p 
  3, 
  which 
  I 
  

   call 
  <p 
  4, 
  as 
  yielding 
  no 
  fossils 
  ; 
  and 
  he 
  doubts 
  the 
  fluviatile 
  origin 
  of 
  both 
  that 
  

   and 
  part 
  of 
  the 
  sands 
  it 
  rests 
  on. 
  See, 
  however, 
  note 
  at 
  page 
  741. 
  

  

  