﻿COKRELATION 
  OP 
  THE 
  BOUENEMOUTH 
  BEDS. 
  13 
  

  

  I 
  have 
  elsewhere 
  endeavoured 
  to 
  show 
  that 
  there 
  was 
  a 
  river 
  of 
  

   large 
  size, 
  bringing 
  deposits 
  from 
  the 
  westward, 
  throughout 
  the 
  

   whole 
  of 
  our 
  Eocenes. 
  The 
  Bournemouth 
  Cliffs, 
  I 
  have 
  long 
  believed, 
  

   present 
  a 
  section 
  across 
  its 
  bed, 
  and 
  were 
  formed 
  during 
  a 
  con- 
  

   tinued 
  period 
  of 
  subsidence. 
  The 
  sudden 
  changes 
  from 
  fine 
  to 
  coarse 
  

   sediment 
  and 
  the 
  thickness 
  of 
  the 
  deposit 
  cannot 
  be 
  explained 
  by 
  the 
  

   floods 
  and 
  freshets 
  incidental 
  to 
  changing 
  seasons, 
  nor 
  by 
  the 
  natural 
  

   meanderings 
  of 
  a 
  river 
  over 
  a 
  wide 
  valley, 
  but 
  are 
  such 
  as 
  would 
  

   occur 
  whenever 
  subsidence 
  exceeded, 
  in 
  however 
  trifling 
  a 
  degree, 
  

   the 
  silting- 
  up 
  power 
  of 
  the 
  river. 
  

  

  A 
  question 
  of 
  importance 
  which 
  must 
  be' 
  raised 
  by 
  the 
  floras 
  found 
  

   in 
  these 
  Bournemouth 
  beds 
  when 
  they 
  are 
  studied, 
  is 
  whether 
  the 
  

   ages 
  of 
  the 
  continental 
  floras 
  similar 
  to 
  ours 
  have 
  been 
  correctly 
  

   determined. 
  While 
  all 
  the 
  strata 
  that 
  have 
  yielded 
  dicotyledonous 
  

   leaves 
  or 
  fruits 
  in 
  England 
  below 
  the 
  Headon 
  series 
  are 
  universally 
  

   admitted 
  to 
  be 
  Eocene, 
  scarcely 
  any 
  of 
  the 
  beds 
  on 
  the 
  continent 
  

   resembling 
  them 
  are 
  ascribed 
  to 
  that 
  age*. 
  

  

  Yet 
  the 
  British 
  Eocenes, 
  exclusive 
  of 
  the 
  Upper 
  Eocenes, 
  or 
  

   Oligocenes, 
  are 
  known 
  to 
  be 
  about 
  1500 
  feet 
  thick, 
  besides 
  the 
  great 
  

   gaps 
  in 
  them, 
  of 
  which 
  there 
  is 
  abundant 
  evidence 
  ; 
  and 
  almost 
  the 
  

   whole 
  of 
  this 
  thickness 
  is 
  an 
  alternation 
  of 
  estuarine 
  and 
  fluviatile 
  

   beds, 
  rich 
  in 
  plant-remains 
  from 
  the 
  highest 
  deposit 
  to 
  the 
  lowest. 
  

  

  Until 
  recently 
  nearly 
  every 
  isolated 
  patch 
  containing 
  a 
  dicotyle- 
  

   donous 
  flora 
  was 
  supposed 
  to 
  be 
  Miocene. 
  This 
  was 
  due 
  to 
  the 
  ac- 
  

   cidental 
  circumstance 
  of 
  the 
  Miocene 
  formation 
  of 
  (Eningen 
  and 
  other 
  

   localities 
  in 
  Central 
  Europe 
  having 
  early 
  attracted 
  attention 
  and 
  been 
  

   described. 
  As 
  all 
  Eocene 
  floras 
  approximate 
  more 
  or 
  less 
  to 
  Miocene, 
  

   it 
  was 
  easy, 
  in 
  the 
  absence 
  of 
  stratigraphical 
  evidence, 
  to 
  assume 
  

   that 
  all 
  isolated 
  patches 
  with 
  dicotyledons 
  belonged 
  to 
  the 
  latter 
  

   period. 
  This 
  classification 
  was 
  greatly 
  favoured 
  by 
  the 
  fact 
  that 
  the 
  

   Middle 
  Eocene 
  floras 
  differ 
  strikingly 
  from 
  the 
  older 
  ones, 
  owing, 
  it 
  

   would 
  seem, 
  to 
  the 
  incoming 
  of 
  a 
  large 
  proportion 
  of 
  plants 
  resem- 
  

   bling 
  existing 
  tropical 
  American 
  species. 
  The 
  great 
  differences 
  seen 
  

   between 
  the 
  older 
  Eocene 
  floras 
  that 
  were 
  partially 
  known 
  (such 
  as 
  

   those 
  of 
  Monte 
  Bolca, 
  Sezanne, 
  Sheppey, 
  Alum 
  Bay) 
  and 
  the 
  Miocene 
  

   floras 
  further 
  supported 
  these 
  views 
  ; 
  and 
  we 
  accordingly 
  find 
  that 
  

   even 
  our 
  own 
  outlying 
  patch 
  of 
  the 
  Middle 
  Bagshot 
  series 
  at 
  Bovey 
  

   Tracey 
  is 
  described 
  as 
  Miocene. 
  In 
  consequence 
  of 
  the 
  position 
  

   assigned 
  to 
  it 
  remaining 
  apparently 
  undisputed, 
  very 
  many 
  other 
  

   formations 
  containing 
  similar 
  floras 
  have 
  been 
  placed 
  in 
  the 
  Miocene 
  ; 
  

   and 
  had 
  the 
  stratigraphical 
  evidence 
  at 
  Bournemouth 
  been 
  inconclu- 
  

   sive, 
  the 
  whole 
  of 
  that 
  Eocene 
  formation 
  must 
  also, 
  upon 
  plant-evi- 
  

   dence, 
  have 
  been 
  classified 
  as 
  Miocene. 
  

  

  In 
  the 
  same 
  manner 
  the 
  true 
  age 
  of 
  the 
  so-called 
  Miocene 
  forma- 
  

  

  * 
  In 
  1874 
  Schimper 
  enumerated 
  the 
  following 
  ferns 
  from 
  beds 
  containing 
  

   dicotyledons 
  : 
  — 
  

  

  Upper 
  Cretaceous 
  (principally 
  Aix-la-Chapelle) 
  46 
  

  

  Pal-eocene 
  (Sezanne) 
  14 
  

  

  Eocene 
  8 
  

  

  Oligocene 
  19 
  

  

  Miocene 
  69 
  

  

  