﻿534 
  MESSES. 
  C. 
  I. 
  GAEDINEE 
  AND 
  S. 
  H. 
  EEYNOLDS 
  ON 
  [Dec. 
  1 
  89 
  7, 
  

  

  of 
  this 
  bed 
  to 
  be 
  about 
  30 
  feet 
  ; 
  it 
  is 
  sometimes 
  overlain 
  by 
  a 
  bed 
  

   of 
  a 
  finer 
  character, 
  which, 
  though 
  it 
  is 
  to 
  a 
  considerable 
  extent 
  

   calcareous, 
  contains 
  no 
  large 
  limestone-pebbles, 
  and 
  is 
  mainly 
  made 
  

   up 
  of 
  small 
  fragments 
  of 
  lava 
  and 
  grit. 
  Above 
  this 
  bed 
  come 
  the 
  

   unaltered 
  grits. 
  

  

  This 
  thrust-conglomerate 
  has 
  obviously 
  been 
  formed 
  by 
  the 
  

   thrusting 
  of 
  the 
  grits 
  over 
  the 
  limestone 
  series 
  ; 
  and 
  the 
  bulk 
  of 
  it 
  has 
  

   been 
  derived 
  from 
  the 
  latter, 
  the 
  tough 
  grits 
  not 
  lending 
  themselves 
  

   readily 
  to 
  its 
  production. 
  The 
  limestone 
  before 
  the 
  disturbance 
  

   must 
  in 
  some 
  places 
  have 
  been 
  of 
  an 
  ashy 
  type, 
  and 
  in 
  others 
  have 
  

   had 
  shaly 
  partings. 
  

  

  VIII. 
  SUMMAEY 
  AND 
  CONCLUSIONS. 
  

  

  In 
  spite 
  of 
  the 
  break 
  between 
  the 
  limestone 
  and 
  the 
  igneous 
  series, 
  

   there 
  seems 
  to 
  be 
  sufficient 
  evidence 
  to 
  prove 
  the 
  general 
  succession 
  

   of 
  the 
  rocks. 
  

  

  The 
  igneous 
  series, 
  of 
  which 
  the 
  lowest 
  beds 
  seen 
  are 
  of 
  the 
  

   nature 
  of 
  lava-flows, 
  is 
  overlain 
  by 
  a 
  coarse 
  ashy 
  conglomerate, 
  

   some 
  of 
  the 
  blocks 
  in 
  which 
  were 
  derived 
  from 
  a 
  neighbouring 
  

   limestone, 
  while 
  others 
  were 
  derived 
  from 
  lava-flows 
  and 
  ash-beds. 
  

   This 
  bed 
  becomes 
  finer 
  in 
  texture 
  as 
  it 
  is 
  traced 
  upward, 
  and 
  

   passes 
  up 
  into 
  finely 
  calcareous 
  ash-beds 
  with 
  intervening 
  bands 
  

   of 
  ashy 
  limestone 
  and 
  shale, 
  which 
  have 
  yielded 
  fossils 
  bearing 
  a 
  

   Middle 
  Bala 
  facies. 
  One 
  of 
  the 
  highest, 
  beds 
  of 
  the 
  series 
  is 
  a 
  bed 
  

   of 
  earthy 
  shale 
  which 
  has 
  yielded 
  fossils, 
  all 
  of 
  which 
  occur 
  in 
  the 
  

   Middle 
  Bala 
  of 
  Great 
  Britain. 
  

  

  The 
  limestone 
  series 
  has 
  at 
  its 
  base 
  many 
  small 
  bands 
  of 
  shale, 
  

   and 
  when 
  the 
  thick 
  bands 
  of 
  limestone 
  come 
  on 
  they 
  are 
  seen 
  to 
  be 
  

   of 
  a 
  distinctly 
  ashy 
  type. 
  The 
  coral-bed 
  in 
  the 
  series 
  is 
  shown 
  by 
  its 
  

   fossils 
  to 
  be, 
  in 
  all 
  probability, 
  of 
  Middle 
  Bala 
  age, 
  and 
  is 
  covered 
  

   immediately 
  by 
  the 
  compact 
  crystalline 
  limestone, 
  which, 
  as 
  noted 
  

   in 
  the 
  Appendix 
  (p. 
  538), 
  is 
  closely 
  comparable 
  to 
  the 
  Sholeshook 
  

   Limestone 
  of 
  South 
  Wales, 
  and 
  is 
  mentioned 
  by 
  Mr. 
  Cowper 
  Eeed 
  

   as 
  being 
  very 
  probably 
  of 
  Upper 
  Bala 
  age. 
  

  

  The 
  succession, 
  though 
  broken, 
  appears 
  therefore 
  to 
  be 
  obvious, 
  

   the 
  break 
  having 
  occurred 
  in 
  the 
  ashy-calcareous 
  rocks 
  intervening 
  

   between 
  the 
  ashy 
  conglomerate 
  and 
  the 
  limestone-beds, 
  but 
  how 
  

   much 
  of 
  the 
  ashy- 
  calcareous 
  rocks 
  has 
  disappeared 
  there 
  is 
  no 
  means 
  

   of 
  telling. 
  There 
  is 
  also 
  no 
  evidence 
  as 
  to 
  the 
  former 
  relation 
  in 
  

   time 
  or 
  in 
  space 
  of 
  the 
  grits 
  between 
  Priest's 
  Chamber 
  and 
  St. 
  Kenny's 
  

   Well 
  to 
  either 
  of 
  the 
  other 
  two 
  series. 
  

  

  The 
  Portraine 
  Limestone, 
  though 
  it 
  has 
  yielded 
  no 
  new 
  species, 
  is 
  

   an 
  important 
  rock, 
  and 
  is 
  comparable 
  to 
  the 
  Chair 
  of 
  Kildare 
  Lime- 
  

   stone 
  on 
  the 
  one 
  hand, 
  and 
  on 
  the 
  other 
  to 
  the 
  Staurocephalus-, 
  

   Keisley, 
  and 
  Sholeshook 
  Limestones 
  of 
  Great 
  Britain. 
  

  

  The 
  igneous 
  rocks, 
  in 
  spite 
  of 
  their 
  being 
  much 
  altered, 
  show, 
  

   though 
  not 
  so 
  well 
  as 
  do 
  those 
  of 
  Lambay 
  Island, 
  that 
  there 
  was 
  an 
  

   active 
  vent 
  in 
  this 
  neighbourhood 
  — 
  apparently 
  in 
  Middle 
  Bala 
  times. 
  

   Where 
  the 
  exact 
  situation 
  of 
  this 
  vent 
  was 
  we 
  have 
  no 
  evidence 
  at 
  

  

  