﻿DRIFT-BEDS 
  OF 
  THE 
  NORTH-WEST 
  OF 
  ENGLAND. 
  33 
  

  

  of 
  the 
  same 
  mineralogical 
  type 
  and 
  most 
  probably 
  from 
  the 
  same 
  pa- 
  

   rent 
  rocks, 
  the 
  larger 
  proportion 
  being 
  scratched 
  and 
  polished. 
  Now 
  

   assuming, 
  as 
  we 
  are 
  justified 
  in 
  doing, 
  that 
  the 
  lower 
  beds 
  of 
  the 
  

   Lancashire 
  clays 
  are 
  older 
  than 
  the 
  Macclesfield 
  and 
  Moel 
  Tryfaen 
  

   drifts*, 
  it 
  is 
  quite 
  evident 
  that 
  in 
  some 
  of 
  the 
  numerous 
  sections 
  I 
  

   shall 
  show 
  you 
  we 
  ought 
  to 
  find 
  representatives 
  of 
  the 
  deposits 
  which 
  

   must 
  have 
  taken 
  place 
  at 
  all 
  depths 
  between 
  the 
  two 
  extremes 
  men- 
  

   tioned, 
  both 
  during 
  subsidence 
  and 
  after 
  elevation. 
  That, 
  however, 
  

   which 
  constitutes 
  the 
  great 
  puzzle, 
  and 
  which 
  led 
  Forbes 
  to 
  iufer 
  the 
  

   drifts 
  to 
  be 
  all 
  shallow-water 
  deposits, 
  is 
  the 
  occurrence 
  of 
  littoral 
  

   shells, 
  the 
  absence 
  of 
  deep-sea 
  corals, 
  and 
  the 
  extremely 
  similar, 
  not 
  

   to 
  say 
  identical, 
  character 
  which 
  they 
  all 
  exhibit. 
  It 
  is 
  true 
  one 
  

   part 
  is 
  more 
  sandy 
  or 
  stony 
  than 
  another, 
  one 
  part 
  contains 
  gravel, 
  

   and 
  another 
  consists 
  almost 
  wholly 
  of 
  a 
  fine 
  unctuous 
  clay 
  ; 
  but 
  

   throughout 
  are 
  the 
  broken 
  and 
  rolled 
  shell-fragments 
  and 
  the 
  

   scratched 
  erratic 
  pebbles 
  and 
  boulders. 
  

  

  It 
  is 
  easy, 
  however, 
  to 
  see 
  that 
  the 
  subsidence 
  and 
  reelevation 
  of 
  

   the 
  land 
  to 
  a 
  vertical 
  extent 
  each 
  way 
  of 
  2000 
  feet 
  must, 
  by 
  the 
  

   deflection 
  of 
  tidal 
  currents 
  (each 
  stage 
  of 
  vertical 
  movement 
  having 
  

   its 
  own 
  proper 
  system 
  of 
  stream 
  -tides), 
  alternately 
  bring 
  every 
  por- 
  

   tion 
  of 
  the 
  sea-bottom 
  under 
  its 
  erosive 
  action. 
  That 
  these 
  tides, 
  

   assisted 
  by 
  winds 
  and 
  storms, 
  must 
  act 
  on 
  the 
  coast-lines 
  and 
  sweep 
  

   off 
  the 
  shells 
  thrown 
  up 
  on 
  the 
  beach, 
  again 
  to 
  distribute 
  their 
  

   fragments 
  over 
  the 
  sea-bottom, 
  is 
  equally 
  evident. 
  That 
  tidal 
  action 
  

   is 
  effective 
  at 
  much 
  greater 
  depths 
  than 
  is 
  generally 
  admitted, 
  I 
  

   have 
  satisfied 
  myself, 
  and, 
  having 
  carefully 
  studied 
  the 
  question, 
  

   shall, 
  I 
  hope, 
  at 
  a 
  future 
  time 
  bring 
  before 
  you 
  sufficient 
  facts 
  to 
  

   prove 
  it. 
  It 
  also 
  presents 
  a 
  probable 
  explanation 
  of 
  much 
  of 
  the 
  

   curious 
  bedding 
  and 
  stratification 
  met 
  with 
  so 
  generally 
  in 
  the 
  

   Drift. 
  From 
  the 
  condition 
  of 
  many 
  of 
  the 
  boulders 
  and 
  pebbles 
  so 
  

   irregularly 
  scratched, 
  and 
  from 
  a 
  consideration 
  of 
  the 
  climatic 
  con- 
  

   ditions 
  of 
  the 
  period, 
  pointed 
  to 
  by 
  many 
  facts, 
  I 
  infer 
  the 
  prevalence 
  

   of 
  coast-ice 
  — 
  an 
  additional 
  cause 
  for 
  the 
  distribution 
  and 
  extreme 
  

   comminution 
  of 
  most 
  of 
  the 
  shell-specimens. 
  It 
  must 
  not 
  be 
  lost 
  

   sight 
  of, 
  if 
  my 
  explanation 
  of 
  the 
  phenomena 
  be 
  correct, 
  that 
  though 
  

   the 
  shells 
  are 
  in 
  fragments, 
  they 
  are 
  (unless 
  they 
  are 
  derivative, 
  of 
  

   which 
  there 
  is 
  no 
  proof) 
  as 
  truly 
  representative 
  of 
  the 
  conditions 
  

   prevailing 
  at 
  the 
  time 
  of 
  their 
  deposition 
  as 
  if 
  they 
  had 
  been 
  found 
  

   on 
  the 
  spot 
  where 
  they 
  died. 
  

  

  4. 
  Analysis 
  of 
  the 
  List, 
  Comparison 
  with 
  the 
  present 
  Molluscous 
  

   Fauna 
  of 
  the 
  British 
  seas, 
  and 
  Inferences 
  therefrom 
  f. 
  

  

  The 
  most 
  generally 
  diffused 
  shell 
  in 
  the 
  Lancashire 
  and 
  Cheshire 
  

  

  * 
  It 
  is 
  necessary 
  to 
  assume 
  this 
  for 
  our 
  present 
  purpose 
  ; 
  but 
  the 
  question 
  will 
  

   be' 
  discussed 
  in 
  extenso 
  and 
  proof 
  given 
  when 
  I 
  deal 
  stratigraphically 
  with 
  the 
  

   beds. 
  

  

  t 
  For 
  the 
  identification 
  of 
  most 
  of 
  the 
  shells 
  I 
  am 
  indebted 
  to 
  Mr. 
  R. 
  D. 
  Dar- 
  

   bishire, 
  F.G.S., 
  who 
  has 
  with 
  great 
  care 
  gone 
  over 
  from 
  time 
  to 
  time 
  some 
  pounds 
  

  

  a. 
  J. 
  G. 
  S. 
  No. 
  117. 
  d 
  

  

  