﻿626 
  PROP. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  

  

  inner 
  shells 
  of 
  the 
  Quarrel-Hill 
  dome, 
  as 
  already 
  described, 
  we 
  have 
  

   had 
  the 
  advantage 
  of 
  possessing 
  easily 
  interpreted 
  sections 
  of 
  long 
  

   extent 
  and 
  tolerably 
  continuous 
  throughout. 
  Among 
  these 
  newer 
  

   and 
  outer 
  beds, 
  on 
  the 
  contrary, 
  the 
  sections 
  are 
  much 
  broken, 
  and 
  

   some 
  of 
  the 
  component 
  zones 
  of 
  the 
  series 
  are 
  represented 
  in 
  isolated 
  

   exposures 
  of 
  very 
  insignificant 
  extent. 
  It 
  follows, 
  therefore, 
  that 
  

   while 
  the 
  general 
  disposition 
  and 
  broader 
  features 
  of 
  the 
  strata 
  are 
  

   easily 
  made 
  out, 
  we 
  are 
  unable 
  to 
  construct 
  a 
  complete 
  ascending 
  

   tabulation 
  of 
  the 
  beds, 
  or 
  say 
  with 
  absolute 
  certainty 
  what 
  special 
  

   thicknesses 
  of 
  rock 
  are 
  locally 
  wanting. 
  

  

  The 
  area 
  occupied 
  by 
  these 
  beds 
  is 
  the 
  extreme 
  north-easterly 
  

   angle 
  of 
  the 
  Lower 
  Pakeozoic 
  inker, 
  and 
  is 
  bounded 
  on 
  both 
  its 
  

   outer 
  margins 
  by 
  faults 
  of 
  great 
  magnitude, 
  at 
  the 
  same 
  time 
  that 
  

   it 
  is 
  more 
  or 
  less 
  cut 
  up 
  by 
  minor 
  dislocations 
  of 
  dubious 
  position. 
  

   Nevertheless 
  the 
  component 
  strata 
  are 
  exhibited 
  in 
  so 
  many 
  ex- 
  

   posures 
  that 
  there 
  can 
  be 
  no 
  great 
  question 
  respecting 
  their 
  general 
  

   arrangement, 
  while 
  they 
  are 
  of 
  such 
  a 
  nature 
  that 
  they 
  admit 
  of 
  

   very 
  convenient 
  subdivision 
  in 
  the 
  field. 
  

  

  Broadly 
  speaking, 
  it 
  may 
  be 
  said 
  that 
  the 
  group 
  is 
  formed 
  of 
  two 
  

   subdivisions 
  — 
  a 
  lower 
  subdivision 
  of 
  flaggy 
  grits, 
  sandstones, 
  con- 
  

   glomerates, 
  and 
  calcareous 
  flags, 
  and 
  a 
  higher 
  subdivision 
  essentially 
  

   composed 
  of 
  Graptolitic 
  shales. 
  

  

  The 
  Lower 
  Subdivision 
  forms 
  a 
  well-marked 
  band 
  about 
  200 
  yards 
  

   in 
  width, 
  ranging 
  parallel 
  with 
  the 
  highest 
  zone 
  of 
  the 
  underlying 
  

   ^Iulloch-Hill 
  beds, 
  from 
  the 
  cottage 
  of 
  Glen 
  wells 
  to 
  the 
  farmhouse 
  

   of 
  Newlands. 
  

  

  Its 
  lowest 
  beds 
  arc 
  exposed 
  at 
  the 
  little 
  burn 
  of 
  Glcnwells, 
  to 
  the 
  

   southward 
  of 
  the 
  Graptolitic 
  mudstones 
  we 
  have 
  referred 
  to 
  the 
  

   Mulloch-Hill 
  group, 
  the 
  intermediate 
  beds 
  being 
  invisible 
  for 
  a 
  

   distance 
  of 
  some 
  40 
  or 
  50 
  yards. 
  These 
  basal 
  beds 
  consist 
  of 
  

   thick-bedded 
  sandstones 
  and 
  flags, 
  with 
  occasional 
  zones 
  of 
  coarse 
  

   conglomerate. 
  The 
  coarsest 
  seams 
  of 
  conglomerate 
  occur 
  at 
  the 
  

   base 
  of 
  the 
  section 
  ; 
  but 
  pebbly 
  beds 
  recur 
  again 
  and 
  again 
  in 
  

   the 
  succession. 
  The 
  matrix 
  of 
  the 
  beds 
  is 
  sandy, 
  aud 
  more 
  or 
  less 
  

   calcareous. 
  About 
  100 
  feet 
  of 
  these 
  strata 
  probably 
  occur 
  in 
  the 
  

   stream 
  itself, 
  between 
  their 
  first 
  appearance 
  above 
  the 
  Graptolitic 
  

   mudstones 
  and 
  the 
  neighbourhood 
  of 
  the 
  cottage 
  of 
  Glcnwells, 
  where 
  

   they 
  are 
  abruptly 
  truncated 
  by 
  the 
  great 
  bounding 
  fault 
  of 
  Kil- 
  

   kerran 
  and 
  Craighead. 
  

  

  The 
  central 
  and 
  upper 
  beds 
  of 
  this 
  subdivision 
  form 
  several 
  

   prominent 
  ridges 
  in 
  the 
  cultivated 
  fields 
  in 
  their 
  prolongation 
  along 
  

   the 
  normal 
  line 
  of 
  strike 
  to 
  the 
  north-east, 
  and 
  in 
  the 
  wooded 
  slopes 
  

   between 
  Glenwells 
  and 
  the 
  farmhouse 
  of 
  Newlands. 
  They 
  afford, 
  

   however, 
  no 
  serviceable 
  exposures, 
  except 
  in 
  the 
  bed 
  of 
  the 
  little 
  

   stream 
  wheh 
  drains 
  the 
  hill-slopes 
  west 
  of 
  the 
  farmhouse, 
  where 
  

   the 
  pebbly 
  gritstones 
  are 
  seen 
  in 
  place 
  close 
  to 
  the 
  farmhouse 
  itself, 
  

   while 
  a 
  series 
  of 
  soft 
  flaggy 
  beds 
  is 
  found 
  a 
  short 
  distance 
  lower 
  

   down 
  the 
  stream. 
  

  

  An 
  old 
  quarry, 
  a 
  few 
  hundred 
  yards 
  north-east 
  of 
  the 
  farm, 
  has 
  

   been 
  excavated 
  in 
  the 
  higher 
  zones 
  of 
  this 
  subdivision. 
  No 
  section, 
  

  

  

  