﻿194 
  W. 
  TOPLEY 
  ON 
  AREAS 
  OF 
  APPARENT 
  UPHEAVAL. 
  

  

  absolutely 
  certain 
  that 
  any 
  observed 
  general 
  dip 
  is 
  wholly 
  due 
  to 
  

   disturbance. 
  The 
  dip 
  may 
  often 
  be 
  so 
  great 
  that 
  we 
  may 
  be 
  quite 
  

   sure 
  that 
  some 
  part 
  of 
  it 
  is 
  due 
  to 
  this 
  cause 
  ; 
  but 
  it 
  will 
  gene- 
  

   rally 
  happen 
  that 
  the 
  proportion 
  of 
  the 
  dip 
  due 
  to 
  disturbance, 
  

   and 
  that 
  due 
  to 
  possible 
  thinning 
  of 
  subjacent 
  beds, 
  cannot 
  be 
  

   determined. 
  

  

  Besides 
  the 
  question 
  of 
  the 
  movements 
  which 
  the 
  earth's 
  crust 
  has 
  

   undergone, 
  there 
  is 
  another 
  question 
  involved 
  in 
  this 
  inquiry, 
  of 
  

   special 
  interest 
  just 
  now 
  ; 
  that 
  is, 
  the 
  influence 
  which 
  such 
  move- 
  

   ments 
  have 
  had 
  in 
  producing 
  the 
  present 
  features 
  of 
  the 
  surface. 
  

  

  Most 
  geologists 
  now 
  believe 
  that 
  this 
  influence 
  has 
  been 
  but 
  small, 
  

   that 
  it 
  has 
  had 
  little 
  or 
  no 
  direct 
  effect 
  in 
  producing 
  the 
  present 
  sur- 
  

   face-features, 
  and 
  that 
  it 
  has 
  only 
  been 
  exerted 
  in 
  guiding 
  the 
  action 
  

   of 
  the 
  denuding 
  agents 
  now 
  quietly 
  at 
  work 
  around 
  us. 
  But 
  others 
  

   still 
  believe 
  that 
  the 
  direct 
  influence 
  of 
  disturbance 
  of 
  the 
  strata 
  has 
  

   been 
  very 
  great. 
  As 
  regards 
  the 
  Weald 
  it 
  has 
  long 
  been 
  held, 
  

   chiefly 
  through 
  the 
  writings 
  of 
  Mr. 
  Martin 
  and 
  Mr. 
  Hopkins, 
  that 
  in 
  

   the 
  original 
  upheaval 
  of 
  that 
  area 
  a 
  system 
  of 
  longitudinal 
  and 
  

   transverse 
  fissures 
  was 
  formed, 
  which 
  not 
  only 
  marked 
  out, 
  but 
  

   immediately 
  form 
  the 
  valley-systems. 
  

  

  It 
  is, 
  perhaps, 
  scarcely 
  necessary 
  to 
  remark 
  that 
  there 
  are 
  other 
  

   signs 
  of 
  disturbance 
  met 
  with 
  in 
  the 
  rocks 
  besides 
  the 
  rise 
  and 
  dip 
  

   of 
  beds. 
  There 
  are 
  sharp 
  flexures 
  and 
  contortions 
  of 
  strata, 
  as 
  well 
  

   as 
  actual 
  fractures 
  and 
  faults, 
  which 
  can 
  only 
  be 
  due 
  to 
  movements 
  

   of 
  the 
  rock-masses. 
  

  

  But, 
  after 
  taking 
  all 
  these 
  fully 
  into 
  account, 
  I 
  believe 
  that, 
  as 
  the 
  

   result 
  of 
  this 
  inquiry, 
  one 
  supposed 
  cause 
  of 
  the 
  formation 
  of 
  surface- 
  

   features 
  is 
  materially 
  weakened 
  ; 
  and 
  yet 
  the 
  fact 
  that 
  great 
  denu- 
  

   dation 
  has 
  taken 
  place 
  remains. 
  Not 
  only 
  so, 
  but 
  the 
  amount 
  of 
  

   denudation 
  which 
  has 
  actually 
  taken 
  place 
  is 
  greater 
  than 
  is 
  gene- 
  

   rally 
  supposed. 
  For 
  if 
  the 
  strata 
  which 
  now 
  remain 
  are 
  thicker 
  at 
  

   their 
  outcrops 
  and 
  at 
  their 
  escarpments 
  than 
  they 
  are 
  further 
  to 
  the 
  

   dip, 
  we 
  may 
  fairly 
  assume 
  that 
  the 
  strata 
  which 
  once 
  stretched 
  

   beyond 
  the 
  present 
  escarpments 
  were 
  thicker 
  than 
  any 
  which 
  are 
  

   still 
  preserved. 
  

  

  Discussion. 
  

  

  The 
  Rev. 
  Mr. 
  Fisher 
  remarked 
  that 
  he 
  had 
  always 
  considered 
  

   that 
  the 
  Palaeozoic 
  rocks 
  under 
  London 
  had 
  formed 
  an 
  axis 
  against 
  

   which 
  the 
  Secondary 
  rocks 
  had 
  abutted, 
  instead 
  of 
  their 
  being 
  carried 
  

   over 
  the 
  old 
  rocks, 
  as 
  shown 
  in 
  the 
  diagram. 
  He 
  presumed 
  that 
  

   there 
  would 
  be 
  difficulty 
  in 
  any 
  natural 
  cause 
  constantly 
  leading 
  to 
  

   the 
  thickening 
  of 
  strata 
  at 
  some 
  particular 
  spot 
  during 
  successive 
  

   epochs 
  so 
  as 
  to 
  form 
  a 
  ridge 
  in 
  a 
  certain 
  position, 
  and 
  argued 
  that 
  

   the 
  shattered 
  condition 
  of 
  the 
  flints 
  in 
  some 
  tilted 
  rocks 
  showed 
  that 
  

   they 
  had 
  been 
  violently 
  upturned. 
  

  

  Mr. 
  Seelet 
  thought 
  the 
  paper 
  extremely 
  suggestive, 
  though 
  pos- 
  

   sibly 
  its 
  suggestiveness 
  had 
  been 
  carried 
  too 
  far. 
  If 
  the 
  author's 
  

   views 
  were 
  correct, 
  the 
  sea 
  in 
  which 
  the 
  beds 
  had 
  been 
  deposited 
  

  

  