﻿PLIOCENE 
  PERIOD 
  IN 
  ENGLAND. 
  683 
  

  

  In 
  this 
  map, 
  No. 
  4, 
  the 
  regions 
  enveloped 
  in 
  land-ice 
  at 
  the 
  time 
  

   of 
  greatest 
  submergence 
  are 
  left 
  unshaded, 
  while 
  the 
  land 
  not 
  so 
  

   enveloped, 
  and 
  which 
  consisted 
  of 
  islands, 
  is 
  shown 
  in 
  black, 
  the 
  sea 
  

   being 
  indicated 
  by 
  a 
  tint 
  of 
  ruled 
  lines. 
  I 
  have 
  not, 
  however, 
  

   attempted, 
  as 
  I 
  have 
  done 
  in 
  the 
  case 
  of 
  the 
  ice 
  of 
  the 
  Chalky 
  Clay, 
  

   to 
  delineate 
  the 
  extent 
  to 
  which, 
  as 
  the 
  land 
  rose, 
  the 
  ice 
  in 
  Lan- 
  

   cashire 
  and 
  Cumberland 
  and 
  that 
  in 
  "Wales 
  advanced. 
  Probably 
  

   as 
  the 
  water 
  was 
  so 
  deep 
  over 
  West 
  Lancashire, 
  the 
  ice 
  there 
  did 
  not 
  

   ever 
  extend 
  beyond, 
  and 
  probably 
  never 
  (at 
  least 
  after 
  the 
  submer- 
  

   gence 
  culminated) 
  reached, 
  the 
  present 
  coast-line 
  of 
  that 
  county* 
  ; 
  

   but 
  it 
  was 
  along 
  the 
  littoral 
  zone 
  which, 
  at 
  the 
  time 
  to 
  which 
  

   Map 
  4 
  applies, 
  skirted 
  the 
  edge 
  of 
  the 
  Lancashire 
  ice 
  that 
  the 
  gravel 
  

   with 
  marine 
  shells 
  accumulated, 
  of 
  which 
  the 
  remnant 
  above 
  Mac- 
  

   clesfield, 
  at 
  1200 
  feet 
  elevation, 
  has 
  escaped 
  the 
  general 
  destruc- 
  

   tion 
  which 
  took 
  place 
  on 
  the 
  advance 
  of 
  the 
  ice 
  during 
  emergence. 
  

   On 
  the 
  parts 
  which 
  represent 
  the 
  corresponding 
  zone 
  skirting 
  the 
  

   Welsh 
  ice, 
  there 
  accumulated 
  similar 
  gravel, 
  of 
  which 
  the 
  remnant 
  

   long 
  known 
  as 
  present 
  at 
  Moel 
  Tryfaen 
  (just 
  beyond 
  the 
  limit 
  of 
  the 
  

   map) 
  at 
  1350 
  feet, 
  by 
  the 
  Menai 
  Strait, 
  and 
  the 
  remnants 
  lately 
  

   discovered 
  by 
  Mr. 
  Mackintosh 
  f 
  on 
  Halkin 
  and 
  Minera 
  mountains, 
  

   at 
  950 
  and 
  1230 
  feet, 
  formed 
  part, 
  and 
  have 
  escaped 
  destruction 
  in 
  

   a 
  similar 
  way. 
  I 
  attribute 
  the 
  escape 
  of 
  all 
  these 
  remnants 
  to 
  the 
  

   ice 
  passing 
  to 
  the 
  sea 
  down 
  the 
  valleys 
  on 
  either 
  side 
  of 
  them 
  as 
  

   emergence 
  went 
  on, 
  leaving 
  these 
  gravel-capped 
  eminences 
  un- 
  

   covered 
  in 
  the 
  way 
  that 
  in 
  Greenland 
  hills 
  not 
  covered 
  by 
  ice 
  

   occur 
  in 
  some 
  places 
  between 
  the 
  great 
  body 
  of 
  the 
  inland 
  ice 
  

   and 
  the 
  sea, 
  and 
  through 
  the 
  valleys 
  beneath 
  which 
  eminences 
  

   this 
  ice 
  escapes 
  as 
  glaciers 
  to 
  the 
  sea. 
  When 
  the 
  great 
  glaci- 
  

   ation 
  passed 
  away, 
  these 
  valleys 
  were 
  reoccupied 
  by 
  the 
  sea 
  up 
  

   to 
  the 
  elevation 
  to 
  which 
  emergence 
  had 
  then 
  lowered 
  the 
  sea-line 
  ; 
  

   and 
  gravel 
  of 
  the 
  same 
  kind, 
  but 
  proportionately 
  later, 
  was 
  then 
  

   deposited 
  in 
  them 
  ; 
  but 
  the 
  molluscan 
  fauna 
  not 
  having 
  altered 
  in 
  

   the 
  interval, 
  the 
  shells 
  in 
  this 
  gravel 
  are 
  much 
  the 
  same 
  as 
  those 
  

   in 
  the 
  gravel 
  of 
  greatest 
  submergence. 
  

  

  It 
  is 
  not 
  easy 
  to 
  perceive 
  why 
  the 
  great 
  Yale 
  of 
  York, 
  and 
  the 
  

   part 
  of 
  North 
  Lincolnshire 
  and 
  of 
  Yorkshire 
  between 
  the 
  Humber 
  

   and 
  the 
  Pennine, 
  has, 
  notwithstanding 
  the 
  presence 
  of 
  the 
  Chalk 
  

   formation 
  far 
  to 
  the 
  north 
  of 
  this, 
  no 
  Chalky 
  Clay 
  in 
  it 
  ; 
  or 
  why 
  the 
  

   Lincolnshire 
  Wold 
  has 
  an 
  enormous 
  moraine 
  of 
  chalk 
  debris 
  heaped 
  

   up 
  on 
  its 
  western 
  flank 
  (though 
  not 
  on 
  its 
  eastern), 
  while 
  the 
  York- 
  

   shire 
  Wold 
  is 
  altogether 
  destitute 
  of 
  this 
  feature. 
  

  

  The 
  explanation 
  seems 
  to 
  be 
  that, 
  as 
  the 
  inclination 
  changed 
  from 
  

   an 
  easterly 
  to 
  a 
  westerly 
  and 
  southerly 
  one, 
  the 
  ice 
  which 
  had, 
  

   during 
  the 
  formation 
  of 
  the 
  Basement 
  Clay 
  of 
  Holderness 
  (B 
  of 
  

   figs. 
  XLVI. 
  to 
  XLIX.), 
  issued 
  through 
  the 
  Humber 
  to 
  the 
  sea 
  which 
  

   had 
  originally 
  been 
  confined 
  to 
  the 
  eastern 
  side 
  of 
  England, 
  was 
  

   deflected 
  southwards 
  to 
  the 
  sea 
  as 
  this 
  extended 
  over 
  the 
  centre 
  and 
  

  

  * 
  The 
  distribution 
  of 
  the 
  Lower 
  Clay 
  of 
  the 
  north-west 
  of 
  England 
  does 
  not 
  

   differ 
  materially 
  from 
  that 
  of 
  the 
  Upper 
  Clay 
  shown 
  in 
  Map 
  5. 
  

   t 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  sxxvii. 
  p. 
  351. 
  

  

  2z2 
  

  

  