﻿654 
  PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GURVAN 
  SUCCESSION. 
  

  

  On 
  the 
  east 
  of 
  the 
  glen, 
  the 
  little 
  stream 
  which 
  crosses 
  the 
  line 
  of 
  

   the 
  Camregan 
  limestone 
  upon 
  the 
  Assel 
  road, 
  and 
  falls 
  into 
  the 
  

   Penwhapple 
  below 
  Penkill 
  Castle, 
  affords 
  an 
  excellent 
  confirmatory 
  

   section 
  of 
  the 
  Crossopodia-shales. 
  Some 
  of 
  the 
  beds 
  of 
  the 
  higher 
  

   greywacke 
  zone 
  are 
  laid 
  open 
  in 
  quarries 
  about 
  half 
  a 
  mile 
  north-east 
  

   of 
  the 
  Castle, 
  where 
  those 
  beds 
  present 
  identical 
  characters 
  with 
  their 
  

   counterparts 
  in 
  Penwhapple, 
  and 
  afford 
  a 
  few 
  examples 
  of 
  Annelid- 
  

   trails 
  and 
  the 
  enigmatical 
  fossil 
  Protovirgularia. 
  

  

  The 
  Burn 
  of 
  Bargany, 
  yet 
  further 
  to 
  the 
  east, 
  crosses 
  the 
  band 
  

   almost 
  at 
  right 
  angles 
  to 
  its 
  course 
  ; 
  but 
  only 
  a 
  few 
  poor 
  sections 
  are 
  

   exposed 
  along 
  it. 
  Such 
  as 
  these 
  are, 
  however, 
  tbey 
  are 
  sufficient 
  to 
  

   prove 
  that 
  the 
  group 
  retains 
  the 
  same 
  soquence 
  and 
  thickness 
  as 
  in 
  

   our 
  typical 
  section. 
  

  

  A 
  few 
  yards 
  west 
  of 
  this 
  burn 
  these 
  strata 
  are 
  unconformably 
  

   overlain 
  by 
  the 
  Old 
  Red 
  Sandstone 
  beds 
  of 
  the 
  Maxwellston 
  Hills. 
  

  

  2. 
  Sections 
  south 
  of 
  Bargany. 
  — 
  The 
  sections 
  we 
  have 
  next 
  to 
  notice 
  

   are 
  found 
  in 
  the 
  steep 
  slopes 
  which 
  overlook 
  the 
  beautifully 
  wooded 
  

   lands 
  of 
  Bargany 
  House, 
  and 
  occur 
  at 
  scattered 
  intervals 
  in 
  that 
  

   long 
  strip 
  of 
  Silurian 
  lying 
  between 
  Penwhapple 
  Glen 
  and 
  the 
  Burn 
  

   of 
  Lindsay's 
  town, 
  about 
  four 
  miles 
  to 
  the 
  eastward. 
  The 
  rocks 
  

   which 
  occupy 
  this 
  subarea 
  are 
  all 
  very 
  similar 
  in 
  their 
  external 
  

   features, 
  consisting 
  of 
  (a) 
  grey 
  and 
  green 
  flagstones 
  and 
  occasional 
  

   greywackes, 
  with 
  dividing 
  seams 
  of 
  shales, 
  and 
  (6) 
  thick 
  zones 
  of 
  

   ribbed 
  shales, 
  arranged 
  in 
  alternating 
  hard 
  and 
  soft 
  bands 
  of 
  an 
  inch 
  

   or 
  two 
  in 
  thickness. 
  They 
  all 
  dip, 
  as 
  a 
  rule, 
  at 
  a 
  steep 
  angle 
  to 
  the 
  

   southward, 
  as 
  if 
  passing 
  below 
  the 
  zone 
  of 
  the 
  Penkill 
  shales 
  last 
  

   described 
  ; 
  but 
  here, 
  as 
  in 
  Penwhapple 
  Glen, 
  this 
  apparent 
  dip 
  is 
  

   delusive, 
  the 
  strata 
  being 
  inverted 
  in 
  geological 
  position. 
  

  

  Near 
  the 
  foot 
  of 
  Penwhapple 
  Glen 
  the 
  most 
  southerly 
  beds 
  of 
  the 
  

   Bargany 
  flagstones 
  are 
  seen 
  in 
  the 
  bed 
  and 
  banks 
  of 
  the 
  stream, 
  

   succeeding 
  and 
  apparently 
  overlying 
  the 
  fossiliferous 
  " 
  Cyrtograptus- 
  

   Qrayi 
  band" 
  with 
  perfect 
  regularity. 
  They 
  consist 
  of 
  grey 
  flags 
  

   varying 
  from 
  six 
  inches 
  to 
  a 
  foot 
  and 
  half 
  in 
  thickness, 
  and 
  are 
  

   divided 
  from 
  each 
  other 
  by 
  similar 
  thicknesses 
  of 
  grey 
  and 
  green 
  

   shales. 
  When 
  split 
  open, 
  the 
  matrix 
  of 
  the 
  generality 
  of 
  the 
  beds 
  

   is 
  seen 
  to 
  be 
  finely 
  levigated 
  and 
  of 
  a 
  peculiar 
  palish 
  blue 
  or 
  

   greyish-green 
  tint, 
  a 
  feature 
  which 
  distinguishes 
  more 
  or 
  less 
  all 
  

   the 
  beds 
  seen 
  in 
  the 
  Bargany 
  area. 
  The 
  harder 
  flags 
  are 
  frequently 
  

   filled 
  with 
  closely 
  approximately 
  transverse 
  fractures 
  and 
  joints, 
  

   which 
  allows 
  of 
  their 
  weathering 
  into 
  a 
  multitude 
  of 
  long 
  angular 
  

   prisms, 
  the 
  outer 
  ends 
  of 
  which 
  are 
  concident 
  with 
  the 
  base 
  and 
  summit 
  

   of 
  the 
  flaggy 
  bed 
  out 
  of 
  which 
  they 
  are 
  formed. 
  These 
  beds 
  fill 
  up 
  

   the 
  final 
  300 
  yards 
  of 
  space 
  which 
  intervene 
  between 
  the 
  C.-Grayi 
  

   band 
  and 
  the 
  great 
  Bargany 
  fault 
  to 
  the 
  north, 
  where 
  the 
  Lower 
  

   Palaeozoic 
  rocks 
  are 
  brought 
  into 
  contact 
  with 
  the 
  greenish-grey 
  

   sandstones 
  oi 
  the 
  Old 
  Red 
  Sandstone 
  of 
  the 
  Girvan 
  valley. 
  These 
  

   Bargany 
  flags 
  are 
  here 
  totally 
  barren 
  ; 
  their 
  visible 
  thickness 
  may 
  

   be 
  estimated 
  at 
  300 
  feet. 
  

  

  A 
  tolerably 
  continuous 
  section 
  of 
  the 
  same 
  flaggy 
  series 
  is 
  seen 
  in 
  

   the 
  course 
  of 
  Bargany 
  Burn, 
  about 
  a 
  mile 
  and 
  half 
  to 
  the 
  eastward 
  

  

  