﻿1864.] 
  MAW 
  SEVERN-VALLEY 
  DRIFT. 
  141 
  

  

  are 
  both 
  southern 
  forms 
  ; 
  and 
  he 
  suggests 
  that 
  they 
  may 
  have 
  been 
  

   intentionally 
  or 
  accidentally 
  introduced 
  into 
  the 
  railway-cutting, 
  or 
  

   brought 
  to 
  me 
  with 
  genuine 
  drift-shells 
  ; 
  but 
  he 
  also 
  remarks 
  that 
  

   the 
  other 
  species 
  do 
  not 
  indicate 
  peculiarly 
  arctic 
  conditions. 
  The 
  

   following 
  species 
  have 
  also 
  been 
  brought 
  me 
  by 
  the 
  navvies, 
  respect- 
  

   ing 
  the 
  occurrence 
  of 
  which 
  similar 
  doubt 
  exists 
  : 
  — 
  Patella 
  vulgata, 
  

   very 
  fresh 
  in 
  appearance 
  and 
  covered 
  with 
  Conferva 
  ; 
  Meleagrina 
  

   margaritifera 
  ; 
  Strombus 
  accipitrinus, 
  a 
  West 
  Indian 
  Shell 
  ; 
  also 
  

   fresh-looking 
  specimens 
  of 
  Purpura 
  lajpillus, 
  Pecten 
  opercularis, 
  and 
  

   Cardium 
  edule. 
  

  

  The 
  Bridgnorth 
  beds 
  have, 
  up 
  to 
  the 
  present 
  time, 
  afforded 
  but 
  a 
  

   single 
  specimen 
  of 
  Purpura 
  lapillus, 
  from 
  the 
  gravel-pits 
  behind 
  St. 
  

   James's, 
  in 
  addition 
  to 
  a 
  few 
  very 
  small 
  fragments 
  of 
  bivalves 
  in 
  the 
  

   Severn-Valley 
  railway-cuttings, 
  two 
  miles 
  south 
  of 
  Bridgnorth. 
  

   In 
  the 
  Buildwas 
  beds, 
  where 
  vast 
  quantities 
  of 
  gravel 
  have 
  been 
  dug 
  

   for 
  ballasting 
  the 
  Severn-Valley 
  and 
  Wenlock 
  Railways, 
  broken 
  

   fragments 
  of 
  Shells 
  also 
  occur, 
  including 
  Cyprina, 
  Cardium, 
  Venus, 
  

   Turritella, 
  and 
  other 
  genera 
  ; 
  but, 
  as 
  they 
  have 
  not 
  been 
  examined 
  

   with 
  the 
  same 
  care 
  as 
  those 
  from 
  the 
  Strethill 
  cutting, 
  a 
  complete 
  

   list 
  cannot 
  be 
  given. 
  

  

  The 
  vegetable 
  remains 
  of 
  the 
  drift-period 
  of 
  the 
  Severn 
  Valley 
  are 
  

   limited 
  to 
  drift-wood, 
  of 
  which 
  some 
  very 
  small 
  fragments 
  have 
  been 
  

   detected 
  in 
  the 
  Buildwas 
  gravels 
  ; 
  and 
  a 
  labourer 
  in 
  my 
  employment 
  

   also 
  informed 
  me 
  that 
  some 
  years 
  ago, 
  when 
  working 
  in 
  the 
  "Willey 
  

   gravel-pits, 
  he 
  came 
  upon 
  a 
  large 
  piece 
  of 
  blackened 
  oak 
  timber. 
  

   I 
  have 
  recently 
  procured 
  some 
  small 
  specimens 
  from 
  the 
  same 
  locality, 
  

   and 
  also 
  a 
  small 
  water-worn 
  fragment 
  of 
  yew 
  wood 
  from 
  the 
  Stret- 
  

   hill 
  clay-bed. 
  

  

  A 
  careful 
  examination 
  of 
  the 
  drift 
  has 
  convinced 
  me 
  that 
  the 
  great 
  

   bulk 
  of 
  the 
  materials 
  of 
  those 
  in 
  the 
  Severn 
  Valley, 
  situated 
  within 
  

   300 
  feet 
  of 
  the 
  sea-level, 
  were 
  certainly 
  of 
  local 
  origin. 
  It 
  will 
  be 
  

   seen 
  from 
  the 
  list 
  of 
  rocks 
  already 
  given 
  that 
  the 
  principal 
  consti- 
  

   tuents 
  of 
  the 
  Strethill 
  deposits 
  now 
  occur 
  in 
  situ, 
  either 
  close 
  at 
  

   hand 
  or 
  within 
  three 
  or 
  four 
  miles. 
  A 
  few, 
  such 
  as 
  the 
  Lias- 
  and 
  

   Chalk-remains, 
  are 
  further 
  removed, 
  and 
  the 
  granite-pebbles 
  and 
  

   boulders 
  appear 
  to 
  have 
  come 
  120 
  miles 
  from 
  the 
  north. 
  At 
  first 
  

   sight, 
  the 
  presence 
  in 
  the 
  drift 
  of 
  such 
  foreign 
  materials 
  furnishes 
  

   evidence 
  of 
  long 
  transit 
  ; 
  but 
  the 
  actual 
  proof 
  of 
  this 
  is 
  only 
  of 
  a 
  

   negative 
  character, 
  as 
  we 
  know 
  not 
  how 
  near 
  such 
  formations 
  as 
  the 
  

   Chalk 
  and 
  Lias 
  originally 
  existed, 
  before 
  the 
  face 
  of 
  the 
  country 
  was 
  

   subject 
  to 
  that 
  erosion 
  which 
  the 
  deposits 
  of 
  the 
  drift 
  represent. 
  

  

  It 
  must 
  be 
  remembered 
  that 
  the 
  mere 
  bulk 
  of 
  a 
  drift-deposit 
  gives 
  

   but 
  slight 
  evidence 
  of 
  the 
  bulk 
  of 
  eroded 
  strata 
  from 
  which 
  it 
  was 
  

   derived. 
  AVe 
  have 
  little 
  evidence 
  to 
  show 
  the 
  proportionate 
  bulk 
  

   which 
  the 
  gravels 
  bear 
  to 
  the 
  finely 
  triturated 
  matter 
  which 
  would 
  

   be 
  carried 
  away 
  in 
  watery 
  suspension, 
  or 
  of 
  the 
  extent 
  to 
  which 
  the 
  

   gravel-beds 
  have 
  been 
  denuded 
  after 
  their 
  first 
  deposition. 
  So 
  that 
  

   whilst, 
  in 
  the 
  existence 
  of 
  drift 
  between 
  200 
  and 
  300 
  feet 
  thick, 
  we 
  

   have 
  strong 
  positive 
  evidence 
  of 
  vast 
  degradation 
  of 
  the 
  older 
  rocks, 
  

   we 
  see 
  no 
  limit 
  to 
  the 
  extent 
  to 
  which 
  that 
  degradation 
  took 
  place 
  

  

  