﻿PLIOCENE 
  PEEIOD 
  US 
  ENGLAND. 
  735 
  

  

  porate 
  with 
  it. 
  The 
  vast 
  hypothesis 
  involved 
  in 
  the 
  filling 
  of 
  the 
  

   North 
  Sea 
  by 
  Scandinavian 
  ice, 
  and 
  the 
  thrusting 
  out 
  of 
  its 
  bed 
  to 
  

   supply 
  molluscan 
  remains 
  to 
  morainic 
  clay 
  in 
  Scotland, 
  so 
  far 
  from 
  

   receiving 
  support 
  from 
  these 
  remains 
  is 
  rather 
  negatived 
  by 
  them 
  ; 
  

   for 
  its 
  advocates 
  have 
  not 
  stopped 
  to 
  consider 
  that 
  the 
  remains 
  thus 
  

   occurring 
  are 
  those 
  only 
  of 
  shells 
  now 
  living 
  in 
  British 
  seas, 
  or 
  in 
  

   the 
  Atlantic 
  immediately 
  north 
  of 
  the 
  British 
  Isles, 
  and 
  do 
  not 
  include 
  

   even 
  the 
  two 
  or 
  three 
  peculiar 
  Crag 
  species 
  which 
  survived 
  into 
  the 
  

   earlier 
  part 
  of 
  the 
  period 
  of 
  the 
  major 
  glaciation, 
  and 
  are 
  found 
  in 
  

   the 
  lower 
  part 
  of 
  the 
  sands 
  bl 
  and 
  at 
  Bridlington, 
  far 
  less 
  the 
  many 
  

   shells 
  of 
  the 
  Upper 
  Crag 
  which 
  had 
  then 
  disappeared 
  from 
  English 
  

   seas. 
  Yet 
  the 
  Eed 
  Crag, 
  of 
  the 
  existence 
  of 
  which 
  in 
  Aberdeenshire, 
  

   as 
  well 
  as 
  Iceland, 
  we 
  get 
  undoubted 
  evidence, 
  and 
  which 
  was 
  the 
  

   deposit 
  of 
  a 
  part 
  of 
  the 
  North 
  Sea, 
  shut 
  in 
  by 
  land 
  extending 
  from 
  

   Essex 
  to 
  Belgium, 
  but 
  open 
  to 
  the 
  north, 
  must 
  have 
  been 
  represented 
  

   by 
  the 
  unconsolidated 
  bottom 
  of 
  the 
  North 
  Sea 
  between 
  Scandinavia 
  

   and 
  Britain 
  immediately 
  antecedent 
  to 
  this 
  glaciation. 
  How, 
  there- 
  

   fore, 
  if 
  this 
  was 
  ploughed 
  out, 
  could 
  the 
  shells 
  peculiar 
  to 
  the 
  Crag 
  

   have 
  escaped 
  being 
  mixed 
  up 
  in 
  the 
  resulting 
  moraine 
  ? 
  

  

  Lastly, 
  as 
  regards 
  the 
  fourth 
  point, 
  the 
  cause 
  of 
  the 
  great 
  refri- 
  

   geration 
  of 
  the 
  Newer 
  Pliocene 
  period, 
  it 
  appears 
  to 
  me 
  that 
  neither 
  

   the 
  theory 
  of 
  Dr. 
  Croll, 
  nor 
  those 
  various 
  modifications 
  of 
  it 
  which 
  

   have 
  been 
  advocated 
  by 
  Mr. 
  A. 
  E. 
  Wallace, 
  Mr. 
  Murphy, 
  and 
  others, 
  

   nor 
  any 
  theory 
  based 
  upon 
  alterations 
  in 
  the 
  distribution 
  of 
  land 
  

   and 
  water 
  are 
  reconcilable 
  with 
  the 
  facts 
  which 
  the 
  study 
  of 
  Newer 
  

   Pliocene 
  geology 
  discloses. 
  The 
  single 
  return 
  of 
  cold 
  evidenced 
  by 
  

   the 
  beds 
  described 
  by 
  me 
  under 
  various 
  representations 
  of 
  the 
  letter 
  

   g, 
  and 
  called 
  by 
  me 
  those 
  of 
  the 
  " 
  minor 
  glaciation," 
  is 
  only 
  that 
  

   which 
  the 
  continental 
  geologists 
  ]ong 
  ago 
  detected 
  in 
  the 
  second 
  

   advance 
  of 
  the 
  Alpine 
  glaciers, 
  and 
  in 
  no 
  way 
  bears 
  out 
  the 
  suc- 
  

   cessive 
  alternations 
  of 
  warm 
  and 
  cold 
  climate 
  postulated 
  by 
  Dr. 
  Croll 
  

   and 
  by 
  some 
  of 
  the 
  modifiers 
  of 
  his 
  theory. 
  Moreover, 
  as 
  it 
  is 
  con- 
  

   ceded 
  by 
  Dr. 
  Croll 
  that 
  the 
  effect 
  of 
  the 
  varying 
  eccentricity 
  in 
  the 
  

   earth's 
  orbit, 
  and 
  the 
  position 
  of 
  the 
  aphelion 
  point 
  in 
  connexion 
  with 
  

   it, 
  would 
  be 
  nil 
  but 
  for 
  the 
  great 
  (and 
  indeed, 
  he 
  says, 
  complete) 
  

   diversion 
  of 
  the 
  ocean-currents, 
  which 
  must, 
  according 
  to 
  his 
  conten- 
  

   tion, 
  accompany 
  it, 
  it 
  is 
  evident 
  that 
  if 
  this 
  were 
  the 
  cause 
  of 
  the 
  

   Glacial 
  period, 
  the 
  isothermal 
  lines 
  of 
  Western 
  Europe 
  and 
  Eastern 
  

   North 
  America, 
  the 
  deflection 
  of 
  which 
  is 
  admitted 
  to 
  be 
  due 
  to 
  the 
  

   Gulf-stream, 
  would 
  not 
  coincide 
  with 
  that 
  proportional 
  increase 
  in 
  

   cold 
  in 
  the 
  respective 
  continents 
  which 
  the 
  evidences 
  of 
  glaciation 
  

   indicate. 
  Yet 
  such 
  coincidence 
  is 
  the 
  case, 
  and 
  the 
  same 
  thing 
  

   appears 
  to 
  hold 
  good 
  of 
  the 
  two 
  sides 
  of 
  North 
  America 
  itself. 
  

   Indeed 
  from 
  all 
  the 
  reports 
  we 
  get 
  of 
  glacial 
  evidences 
  in 
  the 
  

   American 
  and 
  Europseo-Asiatic 
  continents, 
  it 
  seems 
  that, 
  saving 
  the 
  

   extension 
  of 
  the 
  glaciers 
  in 
  mountains, 
  the 
  land-ice 
  accumulated 
  

   during 
  the 
  glaciations 
  only 
  in 
  those 
  regions 
  which 
  at 
  the 
  present 
  

   time 
  are 
  the 
  regions 
  of 
  greatest 
  precipitation 
  ; 
  and 
  this, 
  again, 
  is 
  in- 
  

   consistent 
  with 
  any 
  diversion 
  of 
  the 
  ocean-currents 
  or 
  of 
  the 
  atmo- 
  

   spheric 
  circulation. 
  

  

  