﻿630 
  PROF. 
  C. 
  LAPWOETH 
  ON 
  THE 
  GIEVAN 
  SUCCESSION. 
  

  

  by 
  the 
  stratigraphist 
  to 
  be 
  as 
  easily 
  and 
  satisfactorily 
  reduced 
  to 
  the 
  

   natural 
  order 
  as 
  were 
  the 
  regularly 
  concentric 
  and 
  but 
  slightly 
  

   disturbed 
  strata 
  of 
  the 
  Craighead 
  area. 
  And, 
  indeed, 
  to 
  a 
  large 
  

   extent, 
  this 
  expectation 
  is 
  justified 
  by 
  the 
  event; 
  for 
  had 
  the 
  

   apparent 
  inclination 
  of 
  the 
  strata 
  been 
  trustworthy, 
  there 
  would 
  

   have 
  been 
  no 
  special 
  difficulty 
  in 
  working 
  out 
  the 
  entire 
  sequence 
  

   of 
  the 
  remaining 
  rocks 
  bed 
  by 
  bed 
  ; 
  but, 
  unfortunately, 
  the 
  repeated 
  

   foldings 
  and 
  inversions, 
  so 
  palpable 
  among 
  the 
  underlying 
  Ard- 
  

   millan 
  strata 
  of 
  the 
  Girvan 
  plateau, 
  are 
  here 
  continued 
  and 
  inten- 
  

   sified 
  ; 
  and 
  the 
  problem 
  of 
  the 
  true 
  sequence 
  of 
  the 
  visible 
  zones 
  in 
  

   the 
  strata 
  of 
  the 
  immediate 
  neighbourhood 
  of 
  the 
  Saugh-Hill 
  fault, 
  

   upon 
  more 
  extended 
  examination, 
  appears 
  wellnigh 
  unsolvable. 
  

  

  It 
  will 
  be 
  seen 
  from 
  the 
  map 
  (PI. 
  XXY. 
  1) 
  that 
  a 
  band 
  of 
  Penta- 
  

   mm<s-grits 
  and 
  limestones 
  (C 
  c) 
  forms 
  what 
  may 
  conveniently 
  be 
  

   termed 
  the 
  longitudinal 
  axis 
  of 
  the 
  Lower 
  Palaeozoic 
  region 
  yet 
  to 
  

   be 
  described. 
  This 
  band, 
  which 
  is 
  traceable 
  from 
  end 
  to 
  end 
  of 
  its 
  

   course, 
  from 
  the 
  Braehill 
  fault 
  to 
  the 
  Hadyard 
  Hills, 
  forms 
  a 
  clear 
  

   and 
  easily 
  recognizable 
  horizon, 
  or 
  datum-line, 
  to 
  which 
  to 
  refer 
  the 
  

   less 
  completely 
  exposed 
  strata 
  of 
  the 
  region. 
  North 
  of 
  this 
  band, 
  

   the 
  strata, 
  though 
  inverted 
  in 
  inclination, 
  present 
  no 
  special 
  diffi- 
  

   culties 
  ; 
  but 
  between 
  it 
  and 
  the 
  Saugh-Hill 
  fault, 
  the 
  visible 
  pheno- 
  

   mena 
  demand 
  the 
  most 
  careful 
  scrutiny. 
  

  

  This 
  intermediate 
  area 
  is 
  occupied 
  by 
  a 
  series 
  of 
  hard 
  gritstones 
  

   and 
  fine 
  conglomerates, 
  varied 
  by 
  occasional 
  seams 
  of 
  flagstones, 
  and 
  

   thick 
  bands 
  of 
  green, 
  grey, 
  and 
  black 
  Graptolitiferous 
  shales. 
  A 
  kind 
  

   of 
  rude 
  parallelism 
  is 
  evident 
  among 
  the 
  beds 
  ; 
  but 
  the 
  manner 
  in 
  

   which 
  certain 
  scams 
  appear 
  to 
  thicken 
  out 
  in 
  one 
  locality, 
  and 
  to 
  thin 
  

   away 
  in 
  others, 
  while 
  elsewhere 
  they 
  seem 
  at 
  the 
  first 
  glance 
  to 
  be 
  

   replaced 
  by 
  correspondent 
  groups 
  of 
  wholly 
  distinct 
  petrographical 
  

   characters, 
  forces 
  us 
  to 
  demand 
  a 
  much 
  larger 
  mass 
  of 
  testimony 
  

   in 
  favour 
  of 
  our 
  conclusions 
  than 
  that 
  which 
  has 
  satisfied 
  us 
  in 
  the 
  

   less 
  disturbed 
  areas 
  already 
  described. 
  

  

  (a) 
  Section 
  of 
  the 
  Graptolitic 
  Shales 
  and 
  Grits 
  in 
  Penwhapple 
  Glen. 
  

  

  The 
  deep 
  glen 
  of 
  Penwhapple 
  affords 
  by 
  far 
  the 
  most 
  satisfactory 
  

   and 
  continuous 
  section 
  of 
  these 
  dubious 
  gritstones 
  and 
  shales. 
  They 
  

   follow 
  in 
  immediate 
  geographical 
  succession 
  to 
  the 
  Barren 
  Flagstones 
  

   of 
  that 
  gorge 
  already 
  described, 
  from 
  which 
  they 
  are 
  divided 
  by 
  the 
  

   important 
  Saugh-Hill 
  fault. 
  

  

  Northward 
  from 
  the 
  line 
  of 
  this 
  fault 
  they 
  occupy 
  the 
  bed 
  and 
  

   banks 
  of 
  the 
  stream 
  for 
  about 
  a 
  quarter 
  of 
  a 
  mile 
  of 
  its 
  course, 
  until 
  

   we 
  reach 
  the 
  datum-line 
  of 
  Pentamerus-limestone 
  last 
  mentioned. 
  

  

  The 
  most 
  cursory 
  examination 
  of 
  the 
  grits 
  and 
  shales 
  by 
  one 
  who 
  

   has 
  already 
  studied 
  the 
  strata 
  of 
  Newlands 
  and 
  Glenshalloch, 
  de- 
  

   scribed 
  in 
  the 
  preceding 
  section, 
  is 
  almost 
  sufficient 
  to 
  convince 
  him 
  

   that 
  these 
  beds, 
  as 
  seen 
  in 
  Penwhapple 
  Glen, 
  are 
  identical 
  in 
  their 
  

   lithological 
  features 
  with 
  the 
  yellow 
  grits 
  and 
  Graptolitic 
  flagstones 
  

   of 
  the 
  northern 
  locality 
  ; 
  and 
  whatever 
  doubts 
  he 
  may 
  feel 
  as 
  to 
  

   their 
  general 
  correspondence 
  with 
  the 
  northern 
  strata 
  are 
  soon 
  dis- 
  

   pelled 
  if 
  he 
  take 
  the 
  trouble 
  to 
  collect 
  the 
  fossils 
  from 
  these 
  Pen- 
  

  

  