﻿PLIOCENE 
  PERIOD 
  IN 
  ENGLAND. 
  671 
  

  

  treating 
  in 
  consequence 
  of 
  the 
  diminution 
  in 
  the 
  great 
  Glaciation, 
  the 
  

   outflow 
  of 
  water 
  from 
  it 
  was 
  not 
  due 
  to 
  that 
  ; 
  for 
  this 
  outflow 
  is 
  the 
  

   concomitant 
  of 
  land-ice 
  whether 
  in 
  advance 
  or 
  retreat 
  ; 
  and 
  it 
  is 
  

   estimated 
  by 
  Rink 
  that 
  five 
  sixths 
  of 
  the 
  snow 
  which 
  falls 
  on 
  Green- 
  

   land 
  passes 
  away 
  as 
  water 
  through 
  the 
  land-ice 
  to 
  the 
  sea, 
  the 
  melting 
  

   of 
  the 
  surface 
  of 
  this 
  ice 
  in 
  summer 
  causing 
  rivers 
  to 
  run 
  over 
  it, 
  

   which 
  pour 
  in 
  torrents 
  and 
  cataracts 
  through 
  the 
  fissures 
  in 
  it*. 
  At 
  

   an 
  earlier 
  stage 
  in 
  this 
  retreat 
  — 
  i. 
  e. 
  after 
  the 
  ice 
  had 
  uncovered 
  the 
  

   plateaux 
  of 
  Eastern 
  Norfolk 
  but 
  still 
  occupied 
  the 
  valleys 
  there, 
  

   through 
  which 
  it 
  still 
  reached 
  the 
  North 
  Sea 
  beyond 
  the 
  present 
  

   limit 
  of 
  that 
  county 
  — 
  I 
  have 
  described 
  this 
  water, 
  where 
  it 
  came 
  from 
  

   the 
  ice 
  still 
  lying 
  high 
  on 
  Western 
  Norfolk, 
  as 
  flooding 
  much 
  of 
  

   this 
  uncovered 
  part, 
  and 
  giving 
  rise 
  to 
  the 
  cannon-shot 
  gravel 
  and 
  

   the 
  sand 
  associated 
  with 
  it 
  ; 
  but 
  in 
  general 
  the 
  escape 
  of 
  this 
  

   water 
  is 
  beneath 
  the 
  lowest 
  part 
  of 
  the 
  ice. 
  In 
  Greenland 
  it 
  issues 
  

   from 
  beneath 
  this, 
  where 
  the 
  ice 
  escapes 
  as 
  glaciers 
  through 
  the 
  sea- 
  

   ward 
  extremities 
  of 
  the 
  channels 
  it 
  fills, 
  which 
  are 
  called 
  fiords 
  from 
  

   the 
  point 
  where 
  the 
  ice 
  stops 
  in 
  them. 
  In 
  England 
  these 
  channels 
  

   were 
  the 
  valleys 
  which, 
  having 
  been 
  in 
  existence 
  before 
  the 
  submer- 
  

   gence 
  began, 
  became 
  channels 
  as 
  they 
  went 
  down, 
  and 
  again 
  

   became 
  so 
  during 
  emergence. 
  Since 
  the 
  westward 
  and 
  southward 
  

   extremities 
  of 
  the 
  four 
  Wash 
  valleys 
  already 
  named, 
  where 
  the 
  

   sources 
  of 
  the 
  rivers 
  that 
  now 
  occupy 
  them 
  lie, 
  were 
  more 
  depressed 
  

   than 
  their 
  eastern, 
  proportionally 
  to 
  the 
  westerly 
  and 
  southerly 
  

   increment 
  of 
  depression, 
  and 
  these 
  eastern 
  extremities 
  were 
  blocked 
  

   by 
  the 
  retreating 
  land-ice 
  and 
  by 
  the 
  emergence 
  of 
  Norfolk, 
  the 
  

   effluent 
  water 
  from 
  that 
  ice 
  which 
  issued 
  southwards 
  and 
  west- 
  

   wards 
  along 
  these 
  channels, 
  and 
  was 
  augmented 
  by 
  the 
  drainage 
  

   from 
  the 
  emerged 
  land, 
  had 
  no 
  escape 
  after 
  the 
  partings 
  between 
  

   them 
  and 
  the 
  Thames 
  and 
  Severn 
  systems 
  had 
  emerged 
  ; 
  so 
  that 
  it 
  

   rose 
  and 
  overflowed 
  many 
  of 
  the 
  low 
  partings 
  which 
  separate 
  

   the 
  valleys 
  of 
  the 
  tributaries 
  of 
  these 
  Wash 
  rivers 
  from 
  each 
  

   other, 
  one 
  of 
  which 
  low 
  partings 
  is 
  that 
  of 
  Casewick 
  ; 
  and 
  thus 
  the 
  

   swamp 
  deposit, 
  No. 
  3 
  of 
  Prof. 
  Morris's 
  figure, 
  which, 
  after 
  the 
  ice 
  

   had 
  uncovered 
  this 
  tributary 
  parting, 
  but 
  while 
  the 
  water 
  in 
  the 
  

   valleys 
  had 
  not 
  risen 
  to 
  this 
  level, 
  had 
  been 
  formed 
  upon 
  it, 
  was 
  

   overflowed 
  and 
  covered 
  with 
  gravel 
  by 
  that 
  water. 
  This 
  gravel 
  was 
  

   washed 
  away 
  from 
  the 
  slopes, 
  and 
  left 
  on 
  the 
  low 
  partings, 
  and 
  in 
  

   successive 
  terraces 
  below 
  these 
  partings, 
  as 
  the 
  water-level 
  fell, 
  in 
  the 
  

   way 
  in 
  which 
  it 
  has 
  been 
  supposed 
  to 
  do 
  by 
  those 
  who 
  have 
  attributed 
  

   such 
  gravel 
  to 
  the 
  action 
  of 
  rivers 
  running 
  at 
  these 
  high 
  levels, 
  and 
  

   before 
  the 
  valleys 
  were 
  excavated. 
  

  

  Gravel 
  which, 
  in 
  my 
  view, 
  is 
  of 
  similar 
  age 
  and 
  origin 
  is 
  dis- 
  

   tributed 
  over 
  the 
  drainage-area 
  of 
  the 
  Cam 
  (in 
  central 
  part 
  of 
  Sheet 
  

   51), 
  and 
  crowns 
  tributary 
  river-partings 
  belonging 
  to 
  the 
  Cam 
  system 
  

   in 
  a 
  similar 
  w 
  r 
  ay. 
  Erom 
  its 
  association 
  in 
  places 
  with 
  small 
  beds 
  

   containing 
  freshwater 
  shells, 
  it 
  has 
  been 
  referred 
  by 
  Mr. 
  Jukes-Browne 
  

   to 
  an 
  ancient 
  river-system, 
  the 
  course 
  of 
  which 
  he 
  considers 
  to 
  have 
  

   been 
  in 
  the 
  main 
  almost 
  at 
  right 
  angles 
  to 
  the 
  present 
  river 
  Cam 
  ; 
  

   * 
  Kelland, 
  in 
  vol. 
  xxxiii. 
  of 
  the 
  Journal, 
  p. 
  14.'5. 
  

  

  