﻿DRIFT-BEDS 
  OF 
  THE 
  NORTH-WEST 
  OF 
  ENGLAND. 
  31 
  

  

  3. 
  Mode 
  of 
  Occurrence 
  and 
  Condition 
  of 
  the 
  Shells, 
  &c. 
  

  

  The 
  whole 
  of 
  the 
  shells 
  in 
  the 
  appended 
  list, 
  consisting 
  in 
  all 
  of 
  

   44 
  species, 
  occurred 
  distributed 
  through 
  the 
  drift. 
  In 
  nearly 
  every 
  

   case 
  they 
  were 
  taken 
  from 
  the 
  clay 
  beds 
  ; 
  for 
  though 
  in 
  the 
  included 
  

   sand-seams 
  shells 
  are 
  occasionally 
  met 
  with, 
  they 
  are, 
  as 
  a 
  rule, 
  rare. 
  

   Being 
  small, 
  fragmentary, 
  and 
  rolled, 
  sparsely 
  distributed 
  through 
  

   the 
  clay, 
  and 
  not 
  in 
  any 
  case 
  found 
  in 
  zones 
  or 
  beds, 
  it 
  would 
  be 
  very 
  

   difficult 
  to 
  make 
  a 
  collection 
  from 
  the 
  faces 
  of 
  the 
  clay 
  in 
  excava- 
  

   tions 
  ; 
  but 
  when 
  the 
  clay 
  is 
  " 
  cast 
  " 
  for 
  brick-making, 
  and 
  has 
  been 
  

   subjected 
  to 
  heavy 
  rain, 
  the 
  fragments 
  are 
  weathered 
  out 
  and 
  are 
  

   more 
  readily 
  found. 
  The 
  bulk 
  of 
  my 
  specimens 
  have 
  been 
  obtained 
  

   in 
  this 
  way 
  by 
  my 
  own 
  hands, 
  and 
  are 
  undoubtedly 
  genuine. 
  

  

  Beds 
  or 
  zones 
  of 
  sands 
  containing 
  shells 
  more 
  perfect 
  in 
  their 
  state 
  

   of 
  preservation 
  are, 
  however, 
  occasionally 
  met 
  with 
  ; 
  more 
  perfect 
  

   specimens 
  than 
  mine 
  of 
  some 
  of 
  the 
  species 
  have 
  also 
  been 
  found 
  in 
  

   the 
  clay, 
  such 
  as 
  those 
  taken 
  by 
  Mr. 
  Isaac 
  Roberts, 
  F.G.S., 
  from 
  the 
  

   excavations 
  for 
  the 
  Linacre 
  Gas-works*. 
  The 
  Warrington 
  shells, 
  

   which 
  are, 
  according 
  to 
  Mr. 
  Darbishire, 
  in 
  about 
  the 
  same 
  condition 
  

   as 
  the 
  Blackpool 
  specimens, 
  were 
  (if 
  the 
  locality 
  be 
  correctly 
  de- 
  

   scribed 
  by 
  Mr. 
  Paterson 
  f) 
  taken 
  out 
  of 
  stratified 
  beds 
  of 
  sand 
  and 
  

   gravel, 
  which 
  I 
  have 
  myself 
  inspected 
  in 
  the 
  excavations 
  of 
  theLiver- 
  

   pool 
  Extension 
  Railway 
  near 
  Sankey 
  Bridges. 
  These 
  stratified 
  beds 
  

   bear 
  a 
  closer 
  relationship 
  to 
  the 
  sands 
  and 
  gravels 
  of 
  the 
  so-called 
  

   middle 
  drift 
  at 
  Blackpool 
  than 
  to 
  the 
  clays 
  from 
  which 
  I 
  have 
  obtained 
  

   most 
  of 
  my 
  specimens. 
  

  

  Strange 
  and 
  puzzling 
  as 
  is 
  the 
  condition 
  of 
  the 
  fragments 
  and 
  their 
  

   distribution 
  through 
  the 
  clays, 
  it 
  is 
  one 
  of 
  the 
  main 
  peculiarities 
  

   which 
  should 
  point 
  to 
  a 
  correct 
  interpretation 
  of 
  the 
  way 
  in 
  which 
  

   these 
  beds 
  of 
  drift 
  were 
  laid 
  down. 
  

  

  Professor 
  Forbes, 
  who 
  has 
  remarked 
  on 
  this 
  in 
  his 
  admirable 
  con- 
  

   tribution 
  to 
  the 
  literature 
  of 
  the 
  Glacial 
  periodj, 
  which, 
  even 
  now, 
  

   for 
  comprehensiveness 
  and 
  grasp 
  is 
  unexcelled, 
  and 
  who 
  is 
  evidently 
  

   much 
  puzzled 
  to 
  account 
  for 
  the 
  usual 
  fragmentary 
  character 
  of 
  the 
  

   shells 
  and 
  their 
  tolerably 
  even 
  distribution 
  through 
  the 
  drift, 
  has 
  

   imagined 
  it 
  to 
  be 
  due 
  to 
  the 
  ploughing 
  up 
  of 
  icebergs 
  or 
  the 
  great 
  

   rush 
  of 
  ocean-currents 
  § 
  ; 
  but 
  these 
  suppositions, 
  as 
  I 
  will 
  presently 
  

   show, 
  cannot 
  be 
  more 
  than 
  a 
  limited 
  and 
  partial 
  explanation 
  of 
  a 
  

   general 
  and 
  wide- 
  spread 
  phenomenon. 
  

  

  It 
  is 
  worthy 
  of 
  notice 
  that 
  the 
  shells 
  most 
  generally 
  found 
  whole 
  

   are 
  of 
  a 
  form 
  most 
  calculated 
  to 
  resist 
  pressure, 
  and, 
  in 
  some 
  cases, 
  of 
  

   quite 
  minute 
  dimensions. 
  Turritella 
  terebra, 
  found 
  everywhere 
  in 
  

   the 
  greatest 
  abundance, 
  is 
  not 
  unfrequently 
  perfect. 
  Trophon 
  trun- 
  

   catus 
  and 
  PUurotoma 
  turricula 
  are 
  also 
  found 
  perfect, 
  while 
  the 
  large 
  

   Fusus 
  antiquus, 
  and 
  Buccinum 
  undatum 
  are 
  generally 
  represented 
  

  

  * 
  'Proceedings 
  of 
  the 
  Liverpool 
  Geological 
  Society,' 
  1870-71. 
  p. 
  68. 
  

   f 
  Procceedings 
  of 
  the 
  Warrington 
  Literary 
  and 
  Philosophical 
  Society. 
  

   X 
  " 
  Fauna 
  and 
  Flora 
  of 
  the 
  British 
  Isles," 
  Memoirs 
  of 
  the 
  Geological 
  

   Survey, 
  vol. 
  i. 
  p. 
  383. 
  

   § 
  Ibid. 
  p. 
  384. 
  

  

  