﻿466 
  PROF. 
  J. 
  W. 
  JTTDD 
  ON" 
  THE 
  EOCENE 
  AND 
  OLIGOCENE 
  

  

  of 
  Mr. 
  Meyer 
  * 
  and 
  Mr. 
  Caleb 
  Evans 
  f 
  concerning 
  the 
  equivalent 
  

   strata 
  which 
  were 
  exposed 
  during 
  the 
  Portsmouth-Dockyard 
  ex- 
  

   tension 
  works. 
  The 
  Portsmouth 
  sections, 
  as 
  described 
  by 
  these 
  

   authors, 
  supply 
  us 
  also 
  with 
  the 
  means 
  of 
  bringing 
  into 
  correlation 
  

   the 
  fossiliferous 
  rocks 
  of 
  Bognor, 
  the 
  stratigraphieal 
  position 
  of 
  

   which 
  was 
  before 
  uncertain, 
  and 
  the 
  beds 
  of 
  tho 
  Whitecliff-Bay 
  

   section, 
  which 
  have 
  not 
  yielded 
  a 
  very 
  abundant 
  fauna. 
  

  

  AVhen 
  we 
  proceed 
  westward, 
  however, 
  to 
  Alum 
  Bay, 
  which 
  is 
  

   distant 
  22 
  miles 
  from 
  Whitecliff 
  Bay, 
  there 
  is 
  more 
  difficulty 
  in 
  de- 
  

   termining 
  the 
  exact 
  limits 
  of 
  the 
  Lower 
  Eocene. 
  The 
  carefully 
  

   measured 
  section 
  of 
  the 
  Geological 
  Survey 
  shows 
  the 
  Plastic 
  Clay 
  to 
  

   be 
  only 
  84 
  feet 
  thick, 
  while 
  it 
  assigns 
  219 
  feet 
  of 
  strata 
  to 
  the 
  

   London-Clay 
  series. 
  Mr. 
  Gardner 
  + 
  has 
  argued 
  in 
  favour 
  of 
  in- 
  

   cluding 
  the 
  next 
  176 
  feet 
  of 
  strata 
  in 
  the 
  London-Clay 
  series 
  ; 
  and 
  

   there 
  arc 
  good 
  grounds 
  for 
  adopting 
  his 
  suggestion. 
  This 
  would 
  

   make 
  the 
  Lower 
  Eocene 
  beds 
  at 
  Alum 
  Bay 
  480 
  feet 
  thick, 
  while 
  at 
  

   "Whitecliff 
  Bay 
  they 
  arc 
  500 
  feet. 
  Both 
  the 
  divisions 
  of 
  the 
  Lower 
  

   Eocene 
  are 
  represented 
  at 
  Studland 
  Bay 
  ; 
  but 
  the 
  characters 
  of 
  the 
  

   exposures 
  are 
  not 
  such 
  as 
  to 
  readily 
  admit 
  of 
  the 
  relative 
  thick- 
  

   nesses 
  of 
  the 
  series 
  of 
  strata 
  being 
  accurately 
  determined. 
  

  

  But 
  when 
  we 
  come 
  to 
  the 
  Middle 
  Eocene 
  strata, 
  we 
  find 
  the 
  

   greatest 
  diversity 
  between 
  the 
  views 
  of 
  different 
  authors, 
  both 
  as 
  to 
  

   the 
  limits 
  of 
  the 
  several 
  divisions 
  and 
  their 
  correlation 
  with 
  the 
  

   strata 
  of 
  the 
  London 
  and 
  Paris 
  basins 
  respectively. 
  

  

  In 
  1847, 
  Mr. 
  Prcstwich 
  announced 
  his 
  very 
  important 
  discovery 
  

   that 
  the 
  Bracklesham 
  and 
  Barton 
  beds 
  of 
  the 
  Hampshire 
  basin 
  do 
  

   not 
  represent, 
  as 
  had 
  formerly 
  been 
  supposed, 
  the 
  London 
  Clay, 
  but 
  

   that 
  the 
  former 
  is 
  the 
  exact 
  equivalent 
  of 
  the 
  Calcaire 
  grossier, 
  and 
  

   the 
  latter 
  of 
  the 
  Gres 
  de 
  Beauchamp, 
  or 
  Sables 
  moyens, 
  of 
  the 
  

   Paris 
  basin 
  §. 
  Contemporaneous 
  with 
  this 
  important 
  determination 
  

   was 
  the 
  same 
  author's 
  recognition 
  of 
  the 
  Lower 
  Bracklesham 
  fauna 
  

   in 
  the 
  Middle 
  Bagshot 
  strata 
  of 
  the 
  London 
  basin 
  ||. 
  

  

  Above 
  the 
  strata 
  which 
  at 
  Whitecliff 
  Bay 
  have 
  been 
  shown 
  to 
  be 
  

   the 
  representatives 
  of 
  the 
  London 
  Clay, 
  there 
  occurs 
  a 
  series 
  of 
  

   unf 
  ossiferous 
  sands 
  (Bed 
  5 
  of 
  Prestwich), 
  in 
  all 
  probability 
  of 
  

   freshwater 
  origin. 
  The 
  thickness 
  of 
  these 
  beds 
  has 
  been 
  estimated 
  

   at 
  142 
  feet 
  by 
  Mr. 
  Codrington 
  ; 
  and 
  they 
  were 
  correlated 
  by 
  

   Prof. 
  Prestwich 
  with 
  the 
  Lower 
  Bagshot 
  series 
  in 
  the 
  London 
  basin. 
  

  

  The 
  beds 
  numbered 
  from 
  6 
  to 
  14 
  by 
  Prestwich 
  were, 
  with 
  the 
  

   exception 
  of 
  the 
  upper 
  9 
  feet, 
  referred 
  by 
  that 
  author 
  to 
  the 
  

   Bracklesham 
  series, 
  which, 
  as 
  thus 
  defined, 
  had 
  a 
  thickness 
  of 
  about 
  

   450 
  feet. 
  The 
  beds 
  15 
  to 
  19 
  inclusive, 
  in 
  all 
  about 
  260 
  feet 
  of 
  

   strata, 
  were 
  referred 
  to 
  the 
  Barton 
  Clay. 
  But 
  in 
  1862 
  the 
  Rev. 
  O. 
  

   Fisher 
  proposed 
  to 
  remove 
  more 
  than 
  200 
  feet 
  of 
  the 
  Whitecliff-Bay 
  

   beds 
  from 
  the 
  Barton 
  series 
  and 
  to 
  include 
  them 
  in 
  the 
  Bracklesham 
  

  

  * 
  Quart. 
  Joum. 
  Geol. 
  Soc. 
  vol. 
  xxvii. 
  (1871) 
  p. 
  74. 
  

  

  t 
  Proc. 
  Geol. 
  Assoc. 
  toI. 
  ii. 
  pp. 
  61, 
  149. 
  

  

  + 
  Ibid. 
  vol. 
  vi. 
  p. 
  86. 
  

  

  § 
  Quart. 
  Joum. 
  Geol. 
  Soc. 
  vol. 
  iii. 
  (1847) 
  p. 
  353. 
  

  

  || 
  Ibid. 
  p. 
  378. 
  

  

  