﻿THE 
  EVIDENCE 
  OE 
  FORMER 
  GLACIAL 
  PERIODS. 
  225 
  

  

  periods 
  would 
  thus 
  induce 
  him 
  to 
  give 
  a 
  wrong 
  interpretation 
  of 
  the 
  

   facts. 
  

  

  Assuming 
  that 
  a 
  glacial 
  epoch 
  occurred 
  at 
  every 
  time 
  that 
  the 
  

   earth's 
  orbit 
  attained 
  a 
  very 
  high 
  state 
  of 
  eccentricity, 
  it 
  is 
  quite 
  

   apparent, 
  when 
  Ave 
  reflect 
  on 
  the 
  imperfection 
  of 
  geological 
  records 
  

   on 
  the 
  matter, 
  that 
  we 
  have 
  in 
  reality 
  about 
  all 
  the 
  evidence 
  which 
  

   we 
  could 
  possibly 
  expect 
  of 
  the 
  existence 
  of 
  such 
  epochs. 
  

  

  Discussion. 
  

  

  The 
  President, 
  after 
  alluding 
  to 
  the 
  speculative 
  character 
  of 
  the 
  

   paper, 
  considered 
  that 
  the 
  Author 
  underrated 
  the 
  amount 
  of 
  old 
  

   subaerial 
  surface. 
  Many 
  freshwater 
  deposits, 
  such 
  as 
  the 
  Wealden, 
  

   were 
  fhiviatile 
  and 
  hence 
  subaerial. 
  And 
  if 
  glacial 
  materials 
  had 
  

   then 
  been 
  in 
  the 
  neighbourhood 
  they 
  would 
  have 
  been 
  preserved, 
  as 
  

   was 
  the 
  case 
  in 
  theTalchirs 
  of 
  India, 
  where 
  boulders 
  of 
  considerable 
  

   size 
  were 
  deposited 
  in 
  fluviatile 
  silt. 
  

  

  He 
  doubted 
  the 
  argument 
  about 
  the 
  ice-sheet 
  yielding 
  no 
  erratics, 
  

   and 
  referred 
  to 
  the 
  great 
  moraine 
  across 
  the 
  American 
  continent. 
  

   Moreover, 
  further 
  south 
  than 
  the 
  ice-sheet 
  reached, 
  if 
  there 
  were 
  

   mountains, 
  glaciers 
  would 
  exist 
  and 
  would 
  deposit 
  stones. 
  

  

  Prof. 
  Prestwich, 
  whilst 
  admitting 
  the 
  imperfection 
  of 
  the 
  geolo- 
  

   gical 
  record, 
  thought 
  the 
  Author's 
  view 
  interesting 
  and 
  novel, 
  rather 
  

   than 
  convincing. 
  If 
  glacial 
  periods 
  had 
  formerly 
  existed 
  we 
  should 
  

   not 
  be 
  dependent 
  only 
  on 
  land-surfaces, 
  but 
  the 
  molluscan 
  fauna 
  of 
  

   the 
  arctic 
  seas, 
  and 
  the 
  glacial 
  debris 
  and 
  boulders 
  spread 
  over 
  the 
  

   bed 
  of 
  those 
  seas, 
  would 
  bear 
  evidence 
  of 
  analogous 
  conditions. 
  We 
  

   had 
  in 
  India 
  and 
  Australia 
  some 
  evidence 
  in 
  favour 
  of 
  such 
  con- 
  

   ditions 
  in 
  Permian 
  and 
  Carboniferous 
  times, 
  but 
  these 
  even 
  were 
  

   not 
  yet 
  fully 
  established 
  ; 
  and 
  as 
  to 
  Eocene 
  and 
  Miocene 
  times, 
  he 
  

   would 
  ask 
  what 
  evidence 
  we 
  had 
  there. 
  He 
  knew 
  of 
  none. 
  

   Geology 
  furnished 
  no 
  evidence 
  of 
  periods 
  of 
  recurring 
  cold 
  such 
  as 
  

   Dr. 
  Croll's 
  ingenious 
  and 
  attractive 
  theory 
  required. 
  

  

  Mr. 
  Evans 
  agreed 
  in 
  the 
  remarks 
  of 
  Prof. 
  Prestwich. 
  It 
  seemed 
  

   to 
  him 
  possible 
  that 
  the 
  Author 
  of 
  the 
  paper, 
  finding 
  a 
  difficulty 
  in 
  

   reconciling 
  facts 
  with 
  theory, 
  suggested 
  that 
  the 
  facts 
  insufficiently 
  

   represented 
  past 
  geological 
  histor3 
  T 
  . 
  But 
  whether 
  the 
  theory 
  were 
  

   true 
  or 
  not, 
  glacial 
  conditions 
  must 
  in 
  all 
  probability 
  have 
  prevailed 
  

   in 
  some 
  parts 
  of 
  the 
  globe 
  during 
  all 
  periods, 
  though 
  probably 
  not 
  

   always 
  in 
  the 
  existing 
  centres 
  of 
  glaciatiou 
  ; 
  and 
  of 
  these 
  former 
  

   glacial 
  conditions 
  some 
  evidence 
  was 
  already 
  forthcoming. 
  The 
  

   alleged 
  misconceptions 
  did 
  not 
  seem 
  to 
  him 
  to 
  exist, 
  unless 
  to 
  a 
  

   very 
  small 
  extent 
  ; 
  but 
  still 
  Mr. 
  Croll's 
  communication 
  was 
  of 
  great 
  

   interest. 
  

  

  Prof. 
  Seelet 
  observed 
  that 
  geology 
  was 
  based 
  on 
  inductive 
  evi- 
  

   dence, 
  but 
  in 
  this 
  case 
  it 
  was 
  unsatisfactory 
  to 
  have 
  to 
  deal 
  mainly 
  

   with 
  negative 
  evidence. 
  As 
  Dr. 
  Croll 
  has 
  not 
  attempted 
  to 
  estimate 
  

   the 
  significance 
  and 
  origin 
  of 
  the 
  boulders 
  which 
  occur 
  in 
  many 
  

   geological 
  deposits, 
  we 
  are 
  not 
  bound 
  to 
  do 
  the 
  work 
  for 
  him. 
  Every 
  

   geologist 
  admits 
  that 
  glaciation 
  would 
  be 
  a 
  necessary 
  incident 
  in 
  any 
  

  

  s2 
  

  

  