﻿Geology 
  and 
  Mineralogy. 
  63 
  

  

  were 
  brought 
  about 
  — 
  the 
  luxuriant 
  flora 
  and 
  the 
  great 
  mammals 
  

   of 
  the 
  Pliocene 
  retreating 
  gradually 
  before 
  the 
  approaching 
  win- 
  

   ter 
  of 
  the 
  Glacial 
  Period. 
  

  

  II. 
  First 
  Glacial 
  Epoch. 
  — 
  Eventually 
  a 
  thoroughly 
  arctic 
  

   fauna 
  lived 
  in 
  the 
  North 
  Sea. 
  Great 
  snow-fields 
  at 
  the 
  same 
  time 
  

   came 
  into 
  existence, 
  and 
  a 
  gigantic 
  glacier 
  occupied 
  the 
  basin 
  of 
  

   the 
  Baltic* 
  The 
  mountainous 
  parts 
  of 
  the 
  British 
  Islands, 
  we 
  

   can 
  hardly 
  doubt, 
  must 
  likewise 
  have 
  been 
  ice-clad, 
  but 
  of 
  this 
  

   there 
  is 
  no 
  direct 
  evidence. 
  Farther 
  south 
  the 
  Alpine 
  Lands 
  

   were 
  swathed 
  in 
  snow 
  and 
  ice, 
  and 
  great 
  glaciers 
  occupied 
  all 
  the 
  

   mountain-valleys 
  and 
  piled 
  up 
  their 
  terminal 
  moraines 
  upon 
  the 
  

   low-grounds 
  at 
  the 
  foot 
  of 
  the 
  chain. 
  In 
  Central 
  France 
  very 
  

   considerable 
  glaciers 
  also 
  descended 
  from 
  the 
  great 
  volcanic 
  

   cones 
  of 
  Auvergne 
  and 
  Cantal, 
  and 
  deployed 
  upon 
  the 
  plateaux. 
  

   And 
  probably 
  in 
  many 
  other 
  mountain-districts 
  similar 
  conditions 
  

   obtained. 
  

  

  III. 
  First 
  Interglacial 
  Epoch. 
  — 
  Eventually 
  cold 
  conditions 
  

   passed 
  away. 
  The 
  arctic 
  fauna 
  retreated 
  from 
  the 
  North 
  Sea, 
  and 
  

   at 
  the 
  same 
  time 
  dry 
  land 
  occupied 
  the 
  southern 
  part 
  of 
  that 
  sea 
  

   up 
  to 
  the 
  latitude 
  of 
  Norfolk 
  at 
  least. 
  Across 
  this 
  new-born 
  land 
  

   flowed 
  the 
  Rhine 
  and 
  other 
  rivers. 
  A 
  temperate 
  flora, 
  compara- 
  

   ble 
  to 
  that 
  now 
  existing 
  in 
  England, 
  clothed 
  the 
  land 
  in 
  our 
  lati- 
  

   tude, 
  while 
  the 
  hippopotamus, 
  elephants, 
  deer, 
  and 
  other 
  mam- 
  

   mals 
  became 
  denizens 
  of 
  our 
  country. 
  In 
  other 
  parts 
  of 
  Europe 
  

   similar 
  genial 
  conditions 
  obtained 
  — 
  conditions 
  which, 
  to 
  judge 
  from 
  

   the 
  flora, 
  were 
  even 
  more 
  genial 
  than 
  are 
  now 
  experienced 
  in 
  the 
  

   same 
  regions. 
  A 
  luxuriant 
  deciduous 
  flora 
  occupied 
  the 
  valleys 
  

   of 
  the 
  Alps, 
  and 
  flourished 
  at 
  heights 
  which 
  it 
  no 
  longer 
  attains. 
  

   That 
  flora 
  was 
  accompanied 
  by 
  a 
  mammalian 
  fauna 
  (North 
  Italy) 
  

   which 
  embraced 
  among 
  other 
  forms 
  Elephas 
  meridionalis. 
  From 
  

   the 
  amount 
  of 
  river-erosion 
  effected 
  during 
  this 
  epoch 
  we 
  may 
  

   gather 
  that 
  the 
  stage 
  was 
  one 
  of 
  long 
  duration. 
  By-and-by, 
  how- 
  

   ever, 
  cold 
  conditions 
  again 
  supervened 
  — 
  the 
  temperate 
  flora 
  dis- 
  

   appeared 
  from 
  England, 
  and 
  was 
  gradually 
  replaced 
  by 
  arctic 
  

   forms. 
  

  

  IY. 
  Second 
  Glacial 
  Epoch. 
  — 
  The 
  appearance 
  of 
  that 
  arctic 
  

   flora 
  and 
  the 
  immigration 
  into 
  the 
  North 
  Sea 
  of 
  arctic 
  mollusks 
  

   heralded 
  the 
  approach 
  of 
  the 
  greatest 
  of 
  the 
  European 
  ice-sheets. 
  

   This 
  enormous 
  mer 
  de 
  glace 
  covered 
  all 
  the 
  northern 
  part 
  of 
  the 
  

   Continent 
  and 
  flowed 
  south 
  into 
  Saxony. 
  At 
  the 
  same 
  time 
  the 
  

   Alpine 
  glaciers 
  reached 
  their 
  greatest 
  extension, 
  while 
  in 
  all 
  the 
  

   other 
  mountains 
  of 
  Europe 
  snow-fields 
  and 
  glaciers 
  made 
  their 
  

   appearance. 
  In 
  extraglacial 
  tracts, 
  as 
  in 
  Southern 
  England 
  and 
  

   Northern 
  France, 
  and 
  in 
  many 
  other 
  regions, 
  the 
  formation 
  of 
  

   rock-rubble 
  was 
  in 
  active 
  progress, 
  and 
  much 
  movement 
  of 
  such 
  

   superficial 
  accumulations 
  took 
  place. 
  These 
  physical 
  changes 
  

  

  * 
  The 
  limits 
  reached 
  "by 
  this 
  earliest 
  " 
  great 
  Baltic 
  glacier 
  " 
  are 
  not 
  known. 
  

   In 
  Southern 
  Sweden, 
  however, 
  it 
  occupied 
  a 
  wider 
  area 
  than 
  the 
  great 
  Baltic 
  

   glacier 
  of 
  the 
  fourth 
  glacial 
  epoch, 
  its 
  northern 
  limits 
  lying 
  at 
  least 
  thirty 
  

   miles 
  farther 
  north 
  than 
  those 
  reached 
  by 
  the 
  latter. 
  

  

  