﻿36 
  

  

  T. 
  MELLAED 
  RBADE 
  ON 
  THE 
  

  

  oscillations 
  of 
  level 
  which, 
  occurred 
  during 
  their 
  deposition, 
  that 
  the 
  

   relation 
  of 
  the 
  high-level 
  sands 
  and 
  gravels 
  to 
  the 
  low-level 
  

   Boulder-clays 
  can 
  he 
  satisfactorily 
  made 
  out 
  ; 
  and 
  when 
  this 
  is 
  

   done 
  the 
  palseontological 
  evidence 
  may 
  very 
  properly 
  be 
  taken 
  

   into 
  account. 
  

  

  Considering, 
  then, 
  all 
  the 
  low-level 
  beds 
  as 
  a 
  group, 
  what 
  position 
  

   do 
  they 
  hold 
  in 
  the 
  Glacial 
  series 
  ? 
  Before 
  answering 
  this 
  question 
  it 
  

   will 
  be 
  necessary 
  to 
  glance 
  at 
  the 
  condition 
  of 
  the 
  base-rock 
  upon 
  

   which 
  they 
  generally 
  rest. 
  It 
  may 
  be 
  safely 
  asserted 
  that 
  wherever 
  

   the 
  Boulder-clay 
  is 
  removed 
  in 
  Lancashire 
  and 
  the 
  rock 
  exposed, 
  if 
  

   it 
  is 
  fitted 
  to 
  retain 
  striations 
  and 
  groovings, 
  there 
  they 
  are 
  sure 
  to 
  

   be 
  found. 
  Where 
  the 
  rock 
  is 
  unfitted 
  to 
  receive 
  them, 
  it 
  is, 
  so 
  far 
  

   as 
  my 
  observation 
  extends, 
  ground 
  to 
  powder, 
  broken 
  up 
  into 
  closely 
  

   compacted 
  rubble, 
  or 
  otherwise 
  displaced 
  or 
  shattered. 
  Every 
  thing 
  

   bears 
  evidence 
  of 
  the 
  passage 
  of 
  an 
  ice- 
  sheet 
  over 
  the 
  country 
  in 
  a 
  

   north-westerly 
  direction 
  ; 
  and 
  this, 
  it 
  is 
  needless 
  to 
  say, 
  represents 
  in- 
  

   tense 
  glacial 
  conditions. 
  When, 
  however, 
  we 
  come 
  to 
  the 
  Marine 
  Drift, 
  

   if 
  palseontological 
  evidence 
  is 
  of 
  any 
  value, 
  the 
  climate 
  must 
  have 
  

   been 
  much 
  ameliorated, 
  being 
  probably 
  such 
  as 
  is 
  found 
  in 
  the 
  northern 
  

   parts 
  of 
  Labrador. 
  Thus, 
  then, 
  if 
  my 
  premises 
  be 
  correct, 
  there 
  

   must 
  have 
  been 
  a 
  great 
  break 
  or 
  lapse 
  of 
  time 
  between 
  the 
  cutting 
  

   of 
  the 
  striae 
  and 
  the 
  deposition 
  of 
  the 
  Marine 
  Drift. 
  If 
  so, 
  during 
  this 
  

   period 
  the 
  rocky 
  surface, 
  together 
  with 
  the 
  detritus 
  upon 
  it, 
  must 
  

   have 
  been 
  subject 
  to 
  subaerial 
  conditions; 
  for 
  I 
  can 
  find 
  no 
  evidence 
  

   of 
  any 
  marine 
  clays 
  (though 
  I 
  have 
  examined 
  the 
  base 
  and 
  searched 
  

   for 
  them 
  in 
  many 
  places) 
  older 
  than 
  those 
  forming 
  the 
  subject 
  of 
  this 
  

   paper. 
  

  

  If, 
  on 
  the 
  other 
  hand, 
  we 
  turn 
  our 
  attention 
  to 
  the 
  east 
  coast 
  of 
  

   England 
  and 
  Scotland, 
  we 
  find 
  evidences 
  of 
  much 
  more 
  severe 
  cold 
  

   prevailing 
  during 
  the 
  deposition 
  of 
  some 
  of 
  the 
  beds 
  of 
  Marine 
  Drift 
  

   than 
  any 
  that 
  are 
  to 
  be 
  discovered 
  in 
  Lancashire. 
  The 
  Arctic 
  shells 
  

   found 
  by 
  the 
  Rev. 
  Thos. 
  Brown 
  at 
  Elie 
  in 
  Eifeshire 
  and 
  Errol 
  in 
  Perth- 
  

   shire 
  were 
  declared 
  by 
  Dr. 
  Otto 
  Torel 
  to 
  be 
  identical 
  with 
  species 
  now 
  

   living 
  in 
  front 
  of 
  the 
  great 
  glacier 
  of 
  Spitzbergen*. 
  The 
  Bridlington 
  

   beds, 
  on 
  the 
  coast 
  of 
  Yorkshire, 
  have 
  also 
  yielded 
  a 
  molluscous 
  fauna 
  

   of 
  a 
  more 
  arctic 
  character 
  than 
  either 
  the 
  Lancashire 
  clays 
  or 
  the 
  Clyde 
  

   bedsf. 
  Mr. 
  Searles 
  Wood, 
  jun., 
  whose 
  elaborate 
  investigations 
  of 
  the 
  

   East- 
  Anglian 
  glacial 
  phenomena 
  are 
  of 
  so 
  much 
  value, 
  also 
  considers 
  

   that 
  he 
  has 
  discovered 
  a 
  complete 
  series 
  of 
  beds 
  commencing 
  after 
  the 
  

   Cromer 
  Forest-bed 
  with 
  a 
  crag-like 
  fauna, 
  gradually 
  developing 
  into 
  

   an 
  arctic 
  one, 
  and 
  thence 
  shading 
  down 
  to 
  the 
  Celtic 
  fauna 
  of 
  the 
  

   present 
  seas. 
  If 
  Mr. 
  Wood's 
  reasoning 
  is 
  correct, 
  and 
  be 
  coupled 
  with 
  

   the 
  break 
  I 
  have 
  shown 
  existing 
  between 
  the 
  period 
  of 
  the 
  ice-sheet 
  

   in 
  Lancashire 
  and 
  the 
  deposition 
  of 
  the 
  marine 
  clays, 
  it 
  seems 
  diffi- 
  

   cult 
  to 
  escape 
  from 
  the 
  conclusion 
  that 
  the 
  north-west 
  lowlands 
  were 
  

   under 
  subaerial 
  conditions 
  while 
  the 
  east 
  of 
  England 
  was 
  depressed 
  

   below 
  the 
  sea-level. 
  It 
  would 
  thus 
  also 
  follow 
  that 
  the 
  low-level 
  

   Boulder-clays 
  and 
  sands 
  of 
  Lancashire 
  belong 
  to 
  the 
  later 
  glacial 
  

  

  * 
  Trans, 
  of 
  the 
  Royal 
  Society 
  of 
  Edinb. 
  vol. 
  xxiv. 
  p. 
  627. 
  

   t 
  Quart, 
  Journ. 
  Geol. 
  Soc. 
  1869, 
  p. 
  97. 
  

  

  