﻿PROP. 
  C. 
  LAPWORTH 
  ON 
  THE 
  OIRVAN 
  SUCCESSION. 
  547 
  

  

  Fired 
  by 
  Sedgwick's 
  animated 
  descriptions 
  of 
  the 
  strata 
  of 
  the 
  

   Grirvan 
  region, 
  Sir 
  Roderick 
  Murchison 
  visited 
  the 
  district 
  immedi- 
  

   ately 
  afterwards, 
  in 
  company 
  with 
  his 
  friend 
  Professor 
  Mcol, 
  and 
  

   made 
  a 
  most 
  careful 
  investigation 
  of 
  its 
  Lower 
  Palaeozoic 
  rocks. 
  

   Like 
  Sedgwick, 
  he 
  brought 
  away 
  with 
  him 
  a 
  large 
  collection 
  of 
  the 
  

   most 
  characteristic 
  fossils. 
  These 
  were 
  subsequently 
  submitted 
  to 
  

   the 
  examination 
  of 
  the 
  veteran 
  Silurian 
  palaeontologist, 
  Mr. 
  Salter 
  ; 
  

   and, 
  fortified 
  by 
  the 
  corroborative 
  evidence 
  afforded 
  by 
  these 
  forms, 
  

   Murchison 
  published 
  his 
  results 
  in 
  his 
  general 
  memoir 
  on 
  the 
  

   " 
  Silurian 
  Rocks 
  of 
  the 
  South 
  of 
  Scotland," 
  read 
  before 
  the 
  Society 
  in 
  

   1850, 
  and 
  issued 
  in 
  their 
  Quarterly 
  Journal 
  for 
  1851 
  # 
  . 
  

  

  This 
  memoir 
  is 
  characterized 
  throughout 
  by 
  all 
  Murchison's 
  

   keen 
  geological 
  insight, 
  comprehensive 
  grasp 
  of 
  detail, 
  and 
  

   brilliancy 
  of 
  generalization 
  ; 
  and 
  it 
  remains 
  to 
  this 
  day 
  not 
  only 
  

   classic 
  in 
  respect 
  of 
  its 
  origin, 
  but 
  the 
  clearest, 
  most 
  comprehensive, 
  

   and, 
  if 
  we 
  have 
  respect 
  to 
  the 
  date 
  of 
  its 
  appearance, 
  the 
  most 
  

   reliable 
  paper 
  that 
  has 
  yet 
  been 
  published 
  upon 
  the 
  Lower 
  Palaeozoic 
  

   rocks 
  of 
  this 
  region. 
  

  

  According 
  to 
  Murchison 
  the 
  Silurian 
  strata 
  here 
  displayed 
  consist 
  

   of 
  three 
  main 
  groups 
  — 
  an 
  upper 
  group 
  of 
  schists 
  and 
  flagstones, 
  a 
  

   middle 
  group 
  of 
  shelly 
  sandstones 
  and 
  conglomerates, 
  and 
  a 
  lower 
  

   group 
  of 
  limestones 
  and 
  schists. 
  The 
  highest 
  strata 
  were 
  supposed 
  

   by 
  him 
  to 
  lie 
  in 
  the 
  trough 
  of 
  the 
  apparent 
  synclinal 
  formed 
  by 
  the 
  

   rocks 
  of 
  the 
  great 
  plateau 
  between 
  the 
  valleys 
  of 
  the 
  Girvan 
  and 
  

   Stinchar, 
  and 
  to 
  have 
  their 
  northern 
  representatives 
  in 
  the 
  Trilo- 
  

   bite 
  (l 
  l 
  rinucleus)-sh8iles 
  of 
  Drummuck 
  in 
  the 
  Craighead 
  inlier. 
  His 
  

   middle 
  division 
  embraced 
  the 
  prolific 
  shelly 
  sandstones 
  of 
  Mulloch 
  

   Hill, 
  the 
  Pentamerus-giitstonea 
  of 
  Saugh 
  Hill, 
  and 
  the 
  barren 
  

   boulder- 
  conglomerates 
  of 
  Kennedy's 
  Pass. 
  His 
  lower 
  division 
  was 
  

   supposed 
  to 
  be 
  formed 
  by 
  the 
  limestones 
  of 
  Craighead 
  and 
  the 
  Stin- 
  

   char 
  with 
  their 
  characteristic 
  Maclurea 
  and 
  associated 
  volcanic 
  and 
  

   trappean 
  rocks. 
  

  

  His 
  highest 
  zone, 
  or 
  Orthoceratite- 
  flagstone, 
  had 
  no 
  definite 
  geolo- 
  

   gical 
  date 
  assigned 
  it 
  ; 
  but 
  Murchison 
  had 
  no 
  hesitation 
  in 
  paralleling 
  

   the 
  middle 
  or 
  shelly 
  sandstone 
  division 
  with 
  his 
  typical 
  Caradoc 
  

   Sandstone 
  of 
  Siluria, 
  which 
  at 
  that 
  time 
  included 
  the 
  Pentamerus- 
  

   beds, 
  or 
  Llandovery 
  rocks, 
  as 
  a 
  subordinate 
  member. 
  The 
  Stinchar 
  

   limestones 
  he 
  placed 
  in 
  the 
  Llandeilo, 
  in 
  the 
  lowest 
  or 
  Arenig 
  

   division 
  of 
  that 
  formation 
  as 
  then 
  received, 
  which 
  was 
  supposed 
  

   to 
  be 
  characterized 
  by 
  its 
  many 
  interbedded 
  trappean 
  rocks. 
  

  

  Murchison's 
  conclusions, 
  strengthened 
  as 
  they 
  were 
  by 
  many 
  clear 
  

   sections 
  worked 
  out 
  in 
  the 
  field, 
  were 
  in 
  perfect 
  harmony 
  with 
  the 
  

   ideas 
  then 
  generally 
  entertained 
  with 
  respect 
  to 
  the 
  physical 
  and 
  

   palaeontological 
  succession 
  among 
  the 
  typical 
  Silurian 
  areas 
  of 
  Wales 
  

   and 
  the 
  west 
  of 
  England, 
  and 
  were 
  at 
  once 
  accepted 
  by 
  the 
  majority 
  

   of 
  geologists. 
  

  

  In 
  1854 
  Professors 
  Sedgwick 
  and 
  M'Coy 
  made 
  their 
  famous 
  

   discovery 
  that 
  the 
  May-Hill, 
  or 
  Upper 
  Caradoc 
  Sandstone, 
  or 
  Pen- 
  

   tamerus-heds 
  of 
  Siluria, 
  had 
  no 
  connexion, 
  either 
  physically 
  or 
  

  

  * 
  Quart. 
  Jovirn. 
  Geol. 
  Soc. 
  1851, 
  pp. 
  137 
  et 
  seq. 
  

  

  