﻿DRIFT-BEDS 
  OP 
  THE 
  NORTH-WEST 
  OF 
  ENGLAND. 
  35 
  

  

  occur*. 
  If 
  we 
  turn 
  our 
  attention 
  to 
  the 
  east 
  coast 
  of 
  North 
  America, 
  

   we 
  may 
  find 
  a 
  possible 
  explanation 
  of 
  this 
  curious 
  mixture 
  ; 
  for 
  at 
  

   Cape 
  Cod, 
  in 
  latitude 
  42°, 
  and, 
  I 
  believe, 
  also 
  in 
  higher 
  latitudes, 
  

   arctic 
  and 
  southern 
  forms 
  are 
  now 
  dredged 
  up 
  alive 
  from 
  the 
  same 
  

   bottom 
  f. 
  

  

  5. 
  Position 
  of 
  the 
  Lancashire 
  and 
  Cheshire 
  Low-level 
  Boulder- 
  

   clays 
  AND 
  SANDS 
  IN 
  THE 
  GLACIAL 
  SERIES. 
  

  

  A 
  comparison 
  of 
  my 
  list 
  with 
  that 
  of 
  the 
  shells 
  from 
  the 
  Middle 
  

   drift 
  at 
  Blackpool 
  will 
  hardly, 
  I 
  think, 
  establish 
  the 
  hypothesis 
  often 
  

   broached, 
  that 
  the 
  so-called 
  Middle 
  Drift 
  represents 
  interglacial 
  con- 
  

   ditions. 
  No 
  doubt 
  fluctuations 
  of 
  temperature 
  occurred 
  during 
  the 
  

   laying 
  down 
  of 
  the 
  Boulder-clay 
  series. 
  Though 
  I 
  have 
  found 
  about 
  

   Liverpool 
  a 
  greater 
  number 
  of 
  northern 
  forms 
  than 
  occur 
  in 
  the 
  

   Blackpool 
  sands 
  (the 
  latter 
  being, 
  I 
  consider, 
  but 
  a 
  local 
  develop- 
  

   ment 
  of 
  the 
  Drift), 
  it 
  is 
  impossible 
  to 
  draw 
  with 
  safety 
  wide 
  genera- 
  

   lizations 
  from 
  the 
  palseontological 
  evidence. 
  On 
  the 
  other 
  hand 
  the 
  

   so-called 
  Lower 
  Boulder-clay 
  of 
  Mr. 
  Mackintosh 
  at 
  Dawpool 
  J 
  has 
  

   not 
  yielded 
  him 
  a 
  more 
  northern 
  assemblage 
  thau 
  the 
  Brick 
  or 
  Upper 
  

   Boulder-clay 
  of 
  Lancashire 
  has 
  yielded 
  me 
  §. 
  It 
  is 
  partly 
  on 
  these 
  

   grounds 
  that 
  I 
  have 
  ventured 
  to 
  group 
  together 
  all 
  those 
  beds 
  

   which 
  are 
  typically 
  represented 
  in 
  the 
  Bootle-Lane 
  Station, 
  under 
  the 
  

   title 
  of 
  Low-level 
  Boulder-clays 
  and 
  sands. 
  "Whether 
  or 
  not 
  there 
  

   are 
  stratigraphical 
  grounds 
  for 
  their 
  subdivision 
  will 
  be 
  discussed 
  in 
  

   my 
  concluding 
  paper. 
  

  

  For 
  purposes 
  of 
  comparison 
  I 
  have 
  appended 
  a 
  list 
  of 
  the 
  Moel- 
  

   Tryfaen 
  and 
  Macclesfield 
  shells 
  || 
  ; 
  but 
  though, 
  when 
  compared 
  with 
  the 
  

   Liverpool 
  shells, 
  the 
  former 
  shows 
  a 
  more 
  and 
  the 
  latter 
  a 
  less 
  northern 
  

   facies, 
  I 
  do 
  not 
  think 
  we 
  can 
  safely 
  deduce 
  therefrom 
  the 
  relative 
  

   ages 
  of 
  the 
  Drift 
  in 
  which 
  they 
  occur. 
  Proximity 
  to 
  the 
  mountains 
  

   generating 
  the 
  glaciers 
  may 
  have 
  been 
  the 
  cause 
  in 
  the 
  first 
  case, 
  

   local 
  circumstances 
  in 
  the 
  latter. 
  It 
  is 
  only 
  by 
  a 
  consideration 
  

   of 
  their 
  structure, 
  position, 
  and 
  stratigraphy, 
  combined 
  with 
  the 
  

  

  * 
  Forbes 
  notes 
  the 
  discovery 
  by 
  Captain 
  James 
  of 
  Turritella 
  incrassata, 
  a 
  Crag 
  

   fossil, 
  a 
  southern 
  form 
  of 
  Fusus, 
  and 
  a 
  Mitra 
  allied 
  to 
  the 
  Spanish 
  species 
  in 
  

   the 
  Wexford 
  gravels. 
  

  

  t 
  It 
  must 
  not 
  be 
  lost 
  sight 
  of 
  that 
  glacial 
  conditions 
  in 
  a 
  low 
  latitude 
  would 
  

   produce 
  extremes 
  of 
  heat 
  and 
  cold 
  greater 
  than 
  would 
  occur 
  in 
  a 
  higher 
  latitude 
  

   having 
  the 
  same 
  mean 
  annual 
  temperature, 
  and 
  consequently 
  currents 
  of 
  variable 
  

   temperature 
  would 
  result. 
  Forbes 
  says 
  the 
  distribution 
  of 
  Mollusca 
  depends 
  not 
  

   on 
  latitude 
  but 
  temperature. 
  

  

  | 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxviii. 
  p. 
  388. 
  

  

  § 
  See 
  "Notes 
  on 
  various 
  Shells 
  found 
  in 
  Stratified 
  Drift 
  near 
  Macclesfield," 
  

   Memoirs 
  of 
  the 
  Literary 
  and 
  Philosophical 
  Society 
  of 
  Manchester, 
  Session 
  

   1864-65. 
  

  

  || 
  The 
  Lower 
  Clay 
  of 
  Bootle-Lane 
  Station 
  is 
  an 
  exact 
  counterpart 
  of 
  the 
  Lower 
  

   Clay 
  at 
  Dawpool 
  ; 
  but 
  that, 
  again, 
  yielded 
  me 
  the 
  same 
  characteristic 
  fossils, 
  as 
  

   will 
  be 
  seen 
  on 
  reference 
  to 
  the 
  list. 
  

  

  d2 
  

  

  