﻿672 
  SEARLES 
  Y. 
  WOOD 
  ON 
  THE 
  NEWER 
  

  

  but 
  with 
  this 
  he 
  has 
  associated 
  the 
  Cyrena-gr&vel 
  of 
  Barnwell, 
  

   March, 
  and 
  other 
  Fen 
  localities, 
  which 
  I 
  shall 
  in 
  the 
  sequel 
  describe 
  

   as 
  altogether 
  distinct 
  and 
  posterior*. 
  As 
  an 
  example, 
  he 
  describes 
  

   this 
  gravel 
  of 
  an 
  ancient 
  river-system 
  as 
  crowning 
  a 
  narrow 
  ridge, 
  

   several 
  miles 
  in 
  length, 
  which 
  stretches 
  nearly 
  at 
  right 
  angles 
  to 
  the 
  

   Cam, 
  and 
  is 
  broken 
  through 
  by 
  that 
  river. 
  On 
  the 
  south 
  of 
  the 
  

   Cam 
  this 
  ridge 
  forms 
  the 
  drainage-parting 
  of 
  two 
  streams 
  which 
  

   run 
  parallel 
  and 
  very 
  near 
  to 
  each 
  other 
  ; 
  and 
  his 
  hypothesis 
  is 
  that 
  

   the 
  crest 
  of 
  this 
  ridge 
  represents 
  the 
  bottom 
  of 
  the 
  ancient 
  river, 
  

   which 
  separated 
  into 
  two 
  streams, 
  each 
  of 
  which 
  has 
  cut 
  down 
  

   a 
  valley 
  for 
  itself 
  on 
  either 
  side 
  of 
  the 
  original 
  river. 
  

  

  Space 
  does 
  not 
  allow 
  me 
  to 
  point 
  out 
  all 
  the 
  objections 
  which 
  

   offer 
  themselves 
  to 
  this 
  view 
  ; 
  nor 
  is 
  it 
  necessary 
  to 
  do 
  so, 
  because 
  it 
  

   seems 
  to 
  me 
  that, 
  by 
  referring 
  this 
  gravel 
  to 
  the 
  water 
  just 
  described, 
  

   its 
  position, 
  crowning 
  as 
  it 
  does 
  the 
  parting 
  of 
  two 
  tributaries 
  of 
  one 
  

   of 
  these 
  Wash 
  rivers 
  within 
  the 
  area 
  of 
  that 
  lacustrine 
  expanse, 
  

   is 
  entirely 
  consistent 
  with 
  the 
  conditions 
  which 
  I 
  trace 
  as 
  having 
  

   accompanied 
  the 
  retreat 
  of 
  the 
  ice 
  and 
  emergence 
  of 
  England. 
  It 
  

   should 
  be 
  stated, 
  however, 
  that 
  this 
  gravel 
  passes 
  eastwards 
  into 
  that 
  

   which 
  I 
  have, 
  in 
  the 
  first 
  part 
  of 
  this 
  memoir, 
  described 
  as 
  due 
  to 
  the 
  

   effluent 
  water 
  of 
  the 
  land-ice 
  at 
  an 
  earlier 
  stage 
  of 
  its 
  retreat, 
  and 
  

   before 
  it 
  had 
  ceased 
  to 
  reach 
  Norfolk, 
  — 
  and 
  that 
  southwards 
  Mr. 
  

   Penning 
  (a 
  colleague 
  of 
  Mr. 
  Jukes-Browne 
  in 
  the 
  Geological 
  Survey 
  of 
  

   Cambridgeshire) 
  has, 
  in 
  the 
  Society's 
  Journal 
  (vol. 
  xxxii. 
  p. 
  203), 
  

   described 
  the 
  same 
  gravel 
  as 
  continued 
  by 
  patches 
  " 
  almost 
  to 
  the 
  

   top 
  of 
  the 
  chalk 
  escarpment." 
  These 
  patches, 
  among 
  which 
  are 
  some 
  

   of 
  those 
  referred 
  by 
  Mr. 
  Jukes-Browne 
  to 
  his 
  ancient 
  river-s}'stem, 
  

   Mr. 
  Penning 
  describes 
  as 
  in 
  some 
  places 
  resting 
  on, 
  or 
  else 
  

   taking 
  the 
  place 
  of, 
  the 
  Chalky 
  Clay 
  ; 
  and 
  he 
  gives 
  a 
  succession 
  

   of 
  elevations 
  occupied 
  by 
  them 
  from 
  110 
  up 
  to 
  370 
  feet. 
  He 
  also 
  

   refers 
  them 
  to 
  successive 
  terraces 
  of 
  this 
  supposititious 
  river, 
  

   which 
  must 
  have 
  had 
  its 
  rise 
  at 
  a 
  greater 
  elevation 
  than 
  370 
  feet, 
  

   though 
  within 
  fourteen 
  miles 
  of 
  low-lying 
  Cambridge, 
  and 
  though 
  

   the 
  parting 
  between 
  the 
  drainage 
  to 
  the 
  Cam 
  and 
  that 
  to 
  the 
  

   Thames 
  (by 
  the 
  Stort) 
  hardly 
  reaches 
  300 
  feetf- 
  Looking 
  at 
  

   the 
  physical 
  features 
  of 
  the 
  country 
  drained 
  by 
  the 
  Cam 
  and 
  its 
  

   confluents, 
  and 
  the 
  position 
  also 
  of 
  the 
  Chalky 
  Clay, 
  and 
  of 
  the 
  bed 
  of 
  

   brickearth 
  near 
  Mildenhall 
  and 
  Brandon 
  intercalated 
  in 
  it, 
  such 
  a 
  

   river 
  appears 
  to 
  me 
  an 
  impossibility 
  ; 
  for 
  in 
  a 
  question 
  of 
  this 
  sort 
  

   one 
  group 
  of 
  phenomena 
  alone 
  must 
  not 
  be 
  kept 
  in 
  view 
  and 
  the 
  

   rest 
  ignored, 
  but 
  an 
  explanation 
  must 
  be 
  sought 
  which 
  will 
  bear 
  

   the 
  test 
  of 
  reconciliation 
  with 
  all 
  the 
  other 
  phenomena 
  bearing 
  

   upon 
  the 
  question 
  involved. 
  Now 
  the 
  bed 
  of 
  brickearth 
  at 
  Milden- 
  

   hall, 
  which 
  is 
  overlain 
  by 
  the 
  Chalky 
  Clay 
  as 
  well 
  as 
  underlain 
  by 
  

  

  * 
  Post-tertiary 
  Geology 
  of 
  Cambridgeshire, 
  p. 
  65 
  ct 
  seq. 
  

  

  t 
  The 
  contour-lines 
  of 
  elevation 
  in 
  the 
  Map 
  annexed 
  to 
  Mr. 
  Penning's 
  paper 
  

   show 
  this 
  parting 
  as 
  between 
  300 
  and 
  400 
  feet 
  ; 
  but 
  I 
  have 
  ascertained 
  from 
  the 
  

   Ordnance 
  Survey 
  Office 
  that 
  the 
  whole 
  of 
  this 
  parting 
  (which 
  extends 
  from 
  the 
  

   36^ 
  mile 
  post 
  from 
  London, 
  on 
  the 
  Great 
  Eastern 
  Railway, 
  nearly 
  to 
  the 
  39th) 
  is 
  

   really 
  under 
  300 
  feet, 
  the 
  highest 
  bench-mark 
  (which 
  is 
  302 
  feet) 
  being 
  on 
  a 
  

   bridge 
  over 
  the 
  railway. 
  

  

  