﻿Geology 
  and 
  Mineralogy. 
  65 
  

  

  the 
  beginning, 
  others 
  to 
  the 
  middle 
  of 
  the 
  third 
  interglacial 
  epoch, 
  

   while 
  others 
  again 
  may 
  pertain 
  to 
  its 
  close. 
  They 
  show 
  us 
  clearly, 
  

   however, 
  that 
  after 
  the 
  disappearance 
  of 
  glacial 
  conditions 
  the 
  

   Baltic 
  became 
  tenanted 
  by 
  a 
  temperate 
  North 
  Sea 
  fauna, 
  while 
  

   the 
  adjacent 
  lands 
  supported 
  a 
  corresponding 
  terrestrial 
  fauna 
  

   and 
  flora. 
  

  

  VIII. 
  Fourth 
  Glacial 
  Epoch. 
  — 
  In 
  the 
  early 
  stages 
  of 
  this 
  

   epoch 
  the 
  low-grounds 
  of 
  Scotland 
  were 
  submerged 
  to 
  the 
  extent 
  

   of 
  100 
  ft. 
  at 
  least, 
  while 
  an 
  arctic 
  marine 
  fauna 
  lived 
  round 
  the 
  

   coasts. 
  Eventually 
  the 
  various 
  mountain-districts 
  of 
  our 
  islands 
  

   were 
  cased 
  in 
  snow 
  and 
  ice, 
  large 
  glaciers 
  filling 
  all 
  the 
  Highland 
  

   fiords 
  and 
  calving 
  their 
  icebergs 
  in 
  the 
  sea 
  — 
  a 
  condition 
  of 
  things 
  

   implying 
  a 
  snow-line 
  not 
  exceeding 
  1,000 
  to 
  1,600 
  ft. 
  in 
  elevation. 
  

   But 
  the 
  greatest 
  development 
  of 
  ice 
  was 
  witnessed 
  in 
  the 
  Baltic 
  

   area. 
  The 
  Scandinavian 
  peninsula 
  once 
  more 
  supported 
  an 
  ice- 
  

   sheet 
  that 
  broke 
  away 
  in 
  icebergs 
  at 
  the 
  mouths 
  of 
  all 
  the 
  fiords 
  

   of 
  Western 
  Norway. 
  Finland 
  was 
  well-nigh 
  overwhelmed, 
  while 
  

   the 
  Baltic 
  basin 
  was 
  occupied 
  by 
  a 
  great 
  ice-stream 
  which 
  invaded 
  

   North 
  Germany 
  and 
  Denmark. 
  Later 
  on, 
  as 
  the 
  ice-sheet 
  melted 
  

   away, 
  a 
  wide 
  area 
  in 
  Scandinavia 
  was 
  submerged 
  in 
  a 
  cold 
  sea 
  

   which 
  communicated 
  widely 
  with 
  the 
  Baltic. 
  In 
  the 
  Alps 
  large 
  

   glaciers 
  flowed 
  for 
  long 
  distances 
  down 
  the 
  great 
  valleys, 
  but 
  

   came 
  far 
  short 
  of 
  attaining 
  the 
  dimensions 
  reached 
  by 
  those 
  of 
  

   the 
  preceding 
  glacial 
  epoch. 
  At 
  the 
  same 
  time 
  small 
  local 
  

   glaciers 
  appeared 
  in 
  the 
  high 
  valleys 
  of 
  some 
  of 
  the 
  mountain- 
  

   ranges 
  of 
  Middle 
  Europe. 
  

  

  IX. 
  Fotjrth 
  Interglacial 
  Epoch. 
  — 
  At 
  the 
  climax 
  of 
  this 
  

   epoch 
  temperate 
  conditions 
  prevailed, 
  and 
  extensive 
  forests 
  of 
  

   deciduous 
  trees 
  spread 
  far 
  north 
  into 
  regions 
  where 
  such 
  trees 
  

   no 
  longer 
  flourish. 
  The 
  British 
  Isles 
  now 
  formed 
  part 
  of 
  the 
  

   Continent. 
  The 
  cold 
  sea 
  had 
  retreated 
  from 
  Scandinavia, 
  and 
  

   the 
  Baltic 
  was 
  converted 
  into 
  a 
  great 
  lake. 
  Eventually, 
  how- 
  

   ever, 
  submergence 
  again 
  ensued, 
  but 
  the 
  sea, 
  which 
  now 
  invaded 
  

   Scandinavia 
  and 
  communicated 
  with 
  the 
  Baltic, 
  was 
  tenanted 
  by 
  

   a 
  fauna 
  indicative 
  of 
  more 
  genial 
  conditions 
  than 
  obtain 
  at 
  pres- 
  

   ent. 
  

  

  X. 
  Fifth 
  Glacial 
  Epoch. 
  — 
  This 
  epoch 
  is 
  characteristically 
  

   represented 
  by 
  local 
  or 
  valley 
  moraines 
  in 
  the 
  British 
  Isles, 
  the 
  

   position 
  of 
  which 
  indicates 
  that 
  the 
  snow-line 
  reached 
  in 
  Scotland 
  

   an 
  average 
  height 
  of 
  2,500 
  ft. 
  The 
  disappearance 
  of 
  the 
  genial 
  

   conditions 
  of 
  the 
  preceding 
  temperate 
  epoch 
  was 
  marked 
  by 
  the 
  

   submergence 
  of 
  the 
  Scottish 
  coast-lands 
  to 
  a 
  depth 
  of 
  about 
  fifty 
  

   feet 
  below 
  their 
  present 
  level. 
  Here 
  and 
  there 
  in 
  the 
  northwest 
  

   of 
  Scotland, 
  glaciers 
  reached 
  the 
  sea 
  and 
  dropped 
  their 
  moraines 
  

   on 
  the 
  beaches 
  of 
  the 
  period. 
  To 
  the 
  same 
  epoch 
  may 
  be 
  assigned 
  

   the 
  formation 
  of 
  most 
  of 
  the 
  corrie 
  rock-basins 
  of 
  the 
  British 
  Isles 
  

   — 
  each 
  of 
  these 
  basins 
  marking 
  the 
  site 
  of 
  a 
  glacier 
  of 
  more 
  or 
  

   less 
  limited 
  size. 
  The 
  submergence 
  in 
  Scotland 
  probably 
  com- 
  

   menced 
  in 
  the 
  preceding 
  temperate 
  epoch, 
  as 
  it 
  did 
  likewise 
  in 
  

  

  Am. 
  Joue. 
  Scl— 
  Third 
  Series, 
  Vol. 
  XL1X, 
  No. 
  289.— 
  Jan., 
  1895. 
  

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