﻿GEOLOGICAL 
  CLIMATES 
  SCOTT 
  275 
  

  

  In 
  the 
  interior 
  of 
  the 
  continent, 
  in 
  the 
  region 
  of 
  the 
  northern 
  

   Great 
  Plains, 
  there 
  is 
  a 
  distinct 
  climatic 
  change 
  between 
  the 
  Eocene 
  

   and 
  Oligocene, 
  palms 
  and 
  large 
  crocodiles 
  disappearing 
  from 
  the 
  

   area 
  where 
  they 
  had 
  been 
  prevalent 
  and 
  abundant 
  since 
  the 
  Middle 
  

   Cretaceous. 
  The 
  change, 
  though 
  definite, 
  Avas 
  not 
  extreme, 
  and 
  may 
  

   well 
  have 
  been 
  due 
  rather 
  to 
  an 
  increased 
  altitude 
  than 
  to 
  any 
  gen- 
  

   eral 
  modification 
  of 
  climate. 
  The 
  Miocene 
  flora 
  of 
  central 
  Colorado 
  

   was, 
  except 
  for 
  the 
  absence 
  of 
  palms, 
  much 
  like 
  that 
  of 
  the 
  northern 
  

   Gulf 
  region 
  at 
  present. 
  The 
  gradual 
  refrigeration 
  which 
  marked 
  

   the 
  climatic 
  transition 
  from 
  the 
  warm 
  Miocene 
  to 
  the 
  cold 
  Pliocene 
  

   is 
  best 
  registered 
  in 
  Europe. 
  The 
  German 
  lignites, 
  or 
  brown 
  coals, 
  

   of 
  Miocene 
  date, 
  have 
  preserved 
  a 
  very 
  full 
  representation 
  of 
  the 
  

   plants. 
  In 
  the 
  older 
  lignites 
  the 
  flora 
  is 
  that 
  of 
  the 
  Mediterranean 
  

   lands, 
  with 
  palms 
  and 
  other 
  warm 
  temperate 
  trees, 
  while 
  the 
  upper 
  

   lignites 
  of 
  the 
  same 
  region 
  indicate 
  principally 
  coniferous 
  forests. 
  

   The 
  marine 
  Pliocene 
  beds 
  in 
  the 
  east 
  of 
  England 
  have 
  beautifully 
  

   recorded 
  the 
  oncoming 
  cold. 
  In 
  the 
  lower 
  strata 
  those 
  beds 
  contain 
  

   5 
  per 
  cent 
  of 
  Arctic 
  shells, 
  a 
  proportion 
  which 
  rises 
  to 
  60 
  per 
  cent 
  in 
  

   the 
  upper 
  strata. 
  

  

  In 
  the 
  far 
  north 
  the 
  Pliocene 
  climate 
  must 
  have 
  been 
  severe, 
  as 
  is 
  

   indicated 
  not 
  only 
  by 
  the 
  Arctic 
  species 
  of 
  shells 
  just 
  referred 
  to, 
  but 
  

   also 
  by 
  the 
  Pleistocene 
  mammals, 
  Avhich 
  descended 
  to 
  comparatively 
  

   low 
  latitudes 
  before 
  the 
  advance 
  of 
  the 
  ice. 
  The 
  familiar 
  instances 
  

   of 
  musk 
  oxen 
  in 
  Kentucky 
  and 
  Arkansas, 
  caribou 
  on 
  Long 
  Island 
  

   Sound, 
  seals 
  and 
  walruses 
  on 
  the 
  coast 
  of 
  Georgia, 
  mammoths 
  and 
  

   reindeer 
  in 
  the 
  south 
  of 
  France, 
  lemmings 
  in 
  Portugal, 
  all 
  show 
  a 
  

   complete 
  Arctic 
  assemblage 
  of 
  mammals, 
  both 
  terrestrial 
  and 
  marine. 
  

   These 
  could 
  not 
  have 
  been 
  developed 
  overnight; 
  they 
  must 
  have 
  

   passed 
  through 
  a 
  long 
  period 
  of 
  adaptation 
  to 
  a 
  climate 
  which 
  was 
  

   steadily 
  growing 
  colder. 
  The 
  onset 
  of 
  glacial 
  conditions 
  found 
  a 
  

   fully 
  adapted 
  fauna 
  of 
  Arctic 
  mammals, 
  with 
  nearly 
  uniform 
  cir- 
  

   cumpolar 
  distribution, 
  though 
  some 
  forms, 
  such 
  as 
  the 
  woolly 
  

   rhinoceros, 
  were 
  confined 
  to 
  one 
  or 
  the 
  other 
  continent, 
  for 
  reasons 
  

   that 
  we 
  can 
  not 
  even 
  conjecture. 
  

  

  The 
  interpretation 
  of 
  the 
  Pleistocene 
  deposits, 
  even 
  after 
  their 
  

   icemade 
  character 
  had 
  been 
  generally 
  acknowledged, 
  led 
  to 
  a 
  long- 
  

   drawn-out 
  debate. 
  Was 
  the 
  glacial 
  epoch 
  single 
  or 
  multiple? 
  That 
  

   the 
  ice 
  had 
  been 
  subject 
  to 
  many 
  episodes 
  of 
  advance 
  and 
  retreat 
  

   was 
  admitted; 
  the 
  question 
  was: 
  Were 
  these 
  episodes 
  mere 
  fluctua- 
  

   tions 
  in 
  the 
  extent 
  of 
  the 
  ice 
  sheets, 
  or 
  were 
  there 
  actual 
  interglacial 
  

   times, 
  when 
  the 
  ice 
  altogether 
  disappeared 
  and 
  the 
  climate 
  was 
  

   greatly 
  ameliorated? 
  Time 
  fails 
  me 
  to 
  give 
  any 
  but 
  the 
  most 
  super- 
  

   ficial 
  reference 
  to 
  this 
  famous 
  discussion. 
  Sufficient 
  to 
  say 
  that 
  it 
  is 
  

   the 
  all 
  but 
  unanimous 
  opinion 
  of 
  students 
  of 
  this 
  problem 
  that 
  there 
  

  

  