﻿136 
  

  

  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Jail. 
  20, 
  

  

  indeed, 
  as 
  far 
  as 
  I 
  have 
  been 
  able 
  to 
  ob- 
  

   serve, 
  the 
  mounds 
  of 
  drift 
  which 
  occupy 
  

   so 
  much 
  of 
  the 
  valley 
  up 
  to 
  Shrewsbury 
  

   consist 
  mostly 
  of 
  such 
  beds 
  of 
  sand 
  and 
  

   gravel 
  as 
  occur 
  at 
  the 
  base 
  and 
  the 
  sum- 
  

   mit 
  of 
  Strethill, 
  the 
  middle 
  tough 
  clay- 
  

   deposit 
  being 
  but 
  slightly 
  represented. 
  

   In 
  the 
  cutting 
  opposite 
  Build 
  was 
  Abbey 
  

   and 
  in 
  the 
  gravel-pits 
  near 
  the 
  station, 
  

   the 
  clean 
  sea-sand, 
  similar 
  to 
  that 
  at 
  the 
  

   base 
  of 
  Strethill, 
  is, 
  however, 
  readily 
  dis- 
  

   tinguishable 
  from 
  the 
  upper 
  beds, 
  which 
  

   are 
  greyer 
  in 
  colour 
  and 
  rather 
  more 
  

   clayey 
  in 
  composition, 
  and 
  may 
  possibly 
  

   correspond 
  with 
  the 
  middle 
  beds 
  of 
  Stret- 
  

   hill, 
  though 
  much 
  less 
  tenacious. 
  

  

  Descending 
  the 
  river 
  to 
  Bridgnorth, 
  

   and, 
  for 
  the 
  present, 
  confining 
  our 
  ob- 
  

   servations 
  to 
  the 
  valley, 
  the 
  drift 
  as- 
  

   cends 
  to 
  an 
  altitude 
  of 
  170 
  feet 
  above 
  the 
  

   river 
  (which 
  is 
  here 
  30 
  feet 
  below 
  the 
  

   river 
  at 
  Buildwas) 
  or 
  about 
  240 
  feet 
  

   above 
  the 
  sea. 
  On 
  the 
  east 
  side 
  of 
  the 
  

   valley 
  the 
  drift 
  is 
  disposed 
  in 
  two 
  well- 
  

   marked 
  terraces, 
  their 
  sides 
  sloping 
  at 
  

   an 
  angle 
  of 
  30°, 
  the 
  lower 
  at 
  an 
  alti- 
  

   tude 
  of 
  43 
  feet 
  above 
  the 
  valley-alluvium, 
  

   and 
  the 
  higher 
  43 
  feet 
  above 
  the 
  lower 
  

   terrace, 
  and 
  at 
  altitudes 
  of 
  113 
  and 
  156 
  

   feet 
  above 
  the 
  sea. 
  

  

  The 
  exact 
  correspondence 
  in 
  height 
  of 
  

   these 
  two 
  successive 
  terraces 
  of 
  erosion 
  

   is 
  rather 
  remarkable 
  ; 
  and 
  as 
  they 
  have 
  

   all 
  the 
  appearance 
  of 
  old 
  river-banks, 
  it 
  

   has 
  been 
  suggested 
  by 
  my 
  friend 
  the 
  

   Rev. 
  Mr. 
  Wayne, 
  of 
  Wenlock, 
  that 
  they 
  

   may 
  mark 
  two 
  distinct 
  periods 
  of 
  inter- 
  

   ruption 
  in 
  the 
  elevation 
  of 
  the 
  land 
  — 
  a 
  

   supposition 
  which 
  is 
  well 
  sustained 
  by 
  

   the 
  structure 
  of 
  the 
  crest 
  of 
  the 
  upper 
  

   terrace, 
  a 
  section 
  of 
  which, 
  in 
  the 
  St. 
  

   James's 
  gravel-pits, 
  exposes 
  at 
  one 
  point 
  

   a 
  regular 
  pebble-ridge, 
  or 
  estuary 
  coast- 
  

   beach, 
  composed 
  of 
  rounded 
  boulders 
  

   with 
  but 
  a 
  slight 
  intermixture 
  of 
  smaller 
  

   matter. 
  The 
  bulk 
  of 
  these 
  terraces 
  con- 
  

   sists 
  of 
  an 
  even 
  and 
  stratified 
  inter- 
  

   mixture 
  of 
  gravel 
  and 
  small 
  rounded 
  

   boulders 
  derived 
  from 
  a 
  great 
  variety 
  of 
  

   formations, 
  including 
  the 
  following 
  : 
  — 
  

  

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  o 
  

  

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