﻿718 
  SEAELES 
  V. 
  WOOD 
  Otf 
  THE 
  NEWER 
  

  

  Pursuing 
  what 
  has 
  been 
  already 
  said 
  as 
  to 
  the 
  extent 
  to 
  which 
  

   the 
  depression 
  in 
  which 
  the 
  Cyrena-f 
  ormation 
  originated 
  had 
  been 
  

   recovered, 
  and 
  the 
  pause 
  in 
  the 
  rise 
  took 
  place 
  which 
  was 
  thus 
  coin- 
  

   cident 
  with 
  the 
  extension 
  of 
  the 
  land- 
  ice 
  to 
  the 
  sea 
  in 
  the 
  way 
  just 
  

   described, 
  or, 
  in 
  other 
  words, 
  with 
  the 
  culmination 
  of 
  this 
  minor 
  

   glaciation, 
  we 
  find 
  the 
  buried 
  cliffs 
  of 
  the 
  south 
  fall 
  into 
  their 
  places 
  

   at 
  this 
  point. 
  They 
  all 
  have 
  marine 
  shingle 
  at 
  their 
  base 
  ; 
  and 
  in 
  

   most 
  of 
  this 
  shingle 
  shells 
  occur, 
  all 
  of 
  living 
  British 
  species, 
  save 
  a 
  

   doubtful 
  Rissoa*. 
  Over 
  this 
  shingle, 
  in 
  the 
  cases 
  of 
  Brighton 
  and 
  

   Portland, 
  angular 
  and 
  other 
  boulders 
  of 
  chalk 
  and 
  stone 
  have 
  been 
  

   piled 
  by 
  the 
  pressure 
  of 
  the 
  ice-floes 
  on 
  the 
  shore 
  during 
  the 
  

   minor 
  glaciation, 
  with 
  which 
  seams 
  of 
  loam 
  containing 
  land-shells 
  

   are 
  intermingled 
  ; 
  and 
  as 
  the 
  rise 
  was 
  renewed 
  and 
  the 
  cliffs 
  passed 
  

   out 
  of 
  reach 
  of 
  these 
  floes, 
  they 
  and 
  these 
  boulders 
  and 
  loam 
  became 
  

   buried 
  under 
  the 
  peculiar 
  terrestrial 
  formation 
  due 
  to 
  the 
  atmospheric 
  

   agencies 
  of 
  an 
  arctic 
  climate 
  which 
  I 
  am 
  about 
  to 
  describe, 
  and 
  which 
  

   in 
  my 
  figures 
  is 
  shown, 
  under 
  the 
  letter 
  y, 
  to 
  correspond 
  with 
  the 
  

   formations 
  of 
  synchronous 
  but 
  dissimilar 
  origin 
  shown 
  under 
  the 
  

   letters 
  T, 
  G, 
  G', 
  and 
  g. 
  

  

  In 
  arctic 
  countries, 
  like 
  Siberia, 
  the 
  soil 
  is 
  permanently 
  frozen 
  to 
  a 
  

   considerable 
  depth, 
  only 
  the 
  upper 
  two 
  or 
  three 
  feet 
  of 
  it 
  thawing 
  

   during 
  summer. 
  In 
  this 
  thawing 
  part 
  vegetation 
  not 
  only 
  grows, 
  

   but 
  flourishes. 
  It 
  is 
  obvious, 
  however, 
  that 
  the 
  part 
  below 
  remain- 
  

   ing 
  frozen 
  is 
  impermeable 
  by 
  water, 
  so 
  that, 
  as 
  this 
  can 
  have 
  no 
  

   escape 
  vertically, 
  it 
  must 
  convert 
  the 
  thawed 
  layer 
  into 
  sludge 
  ; 
  the 
  

   tendency 
  of 
  which 
  is 
  to 
  slide 
  horizontally 
  from 
  higher 
  to 
  lower 
  

   ground, 
  thus 
  accumulating 
  more 
  and 
  more 
  in 
  depressions, 
  and 
  expo- 
  

   sing 
  more 
  and 
  more 
  of 
  the 
  surface 
  from 
  which 
  it 
  slid 
  to 
  the 
  opera- 
  

   tion 
  of 
  this 
  agency, 
  and 
  so 
  keeping 
  up 
  the 
  supply. 
  The 
  frost 
  and 
  

   thaw 
  thus 
  acting 
  upon 
  limestone-rock, 
  which 
  is 
  partially 
  porous, 
  has 
  

   split 
  it 
  up 
  into 
  angular 
  fragments, 
  which 
  became 
  dispersed 
  in 
  the 
  

   resulting 
  sludge 
  ; 
  and 
  the 
  same 
  thing 
  acting 
  upon 
  the 
  flints 
  in 
  the 
  

   chalk 
  split 
  them 
  into 
  splinters, 
  which 
  have 
  become 
  dispersed 
  in 
  like 
  

   manner 
  t. 
  In 
  the 
  case 
  of 
  the 
  major 
  glaciation 
  those 
  islands 
  of 
  chalk 
  

   shown 
  in 
  Sheets 
  46, 
  13, 
  and 
  34 
  of 
  Map 
  4, 
  as 
  not 
  reached 
  by 
  the 
  

   chalky 
  clay, 
  are 
  covered 
  with 
  the 
  atmospheric 
  formation 
  thus 
  re- 
  

   sulting 
  during 
  that 
  period, 
  which 
  is 
  the 
  clay 
  with 
  flints 
  ; 
  and 
  in 
  the 
  

   case 
  of 
  the 
  pebble-beds 
  of 
  South 
  Essex, 
  shown 
  in 
  fig. 
  VI. 
  by 
  the 
  

   number 
  VIII., 
  and 
  which 
  became 
  land 
  at 
  an 
  early 
  part 
  of 
  the 
  

   emergence, 
  this 
  agency, 
  while 
  the 
  land-ice 
  filled 
  the 
  valleys 
  shown 
  in 
  

  

  * 
  Neither 
  of 
  the 
  two 
  peculiarly 
  Lusitanian 
  species 
  of 
  the 
  Selsea 
  bed 
  occur 
  

   among 
  them 
  ; 
  and 
  the 
  whole 
  assemblage 
  is 
  the 
  reverse 
  in 
  character 
  of 
  the 
  

   Mollusca 
  of 
  that 
  bed 
  ; 
  for 
  while 
  the 
  rest 
  of 
  the 
  species 
  there, 
  other 
  than 
  

   these 
  two 
  Lusitanian, 
  constitute 
  an 
  assemblage 
  characteristic 
  of* 
  our 
  present 
  

   south 
  -coast, 
  Mr. 
  Jeffreys 
  observes 
  (Journal, 
  vol. 
  xxxi. 
  p. 
  52) 
  that 
  the 
  shells 
  

   collected 
  by 
  Mr. 
  Prestwich 
  from 
  the 
  beach 
  at 
  the 
  foot 
  of 
  the 
  buried 
  cliff 
  at 
  

   Portland 
  " 
  are 
  rather 
  northern 
  than 
  southern 
  " 
  in 
  their 
  type. 
  

  

  t 
  This 
  slide 
  of 
  the 
  soil-cap 
  takes 
  place 
  now 
  in 
  Patagonia 
  from 
  the 
  wetness 
  

   of 
  the 
  climate 
  alone, 
  according 
  to 
  Dr. 
  Coppinger, 
  in 
  vol. 
  xxxvii. 
  of 
  the 
  Journal, 
  

   p. 
  348. 
  A 
  fortiori, 
  would 
  this 
  go 
  on 
  under 
  the 
  conditions 
  described 
  in 
  the 
  text 
  ; 
  

   while 
  wetness 
  of 
  climate 
  would 
  not 
  rupture 
  the 
  limestone 
  into 
  fragments, 
  or 
  the 
  

   flints 
  into 
  splinters, 
  such 
  as 
  abound 
  in 
  the 
  formation 
  I 
  am 
  describing. 
  

  

  