﻿Vol. 
  53«] 
  THE 
  POKTRAINE 
  INLIER 
  (CO. 
  DUBLIN). 
  523 
  

  

  mass 
  of 
  coarse 
  rock, 
  similar 
  in 
  character 
  to 
  the 
  dyke 
  above 
  

   mentioned. 
  It 
  appears 
  to 
  be 
  intruded 
  into 
  the 
  surrounding 
  ande- 
  

   sites, 
  portions 
  of 
  which 
  are 
  caught 
  up 
  and 
  included 
  in 
  it. 
  It 
  

   contains 
  in 
  some 
  parts 
  numerous 
  jaspers. 
  

  

  Farther 
  to 
  the 
  south-east 
  a 
  small 
  thickness 
  of 
  light-green 
  andesite 
  

   is 
  seen 
  dipping 
  S.E., 
  at 
  an 
  angle 
  of 
  about 
  45° 
  ; 
  and 
  then, 
  after 
  

   a 
  gap 
  in 
  the 
  exposures, 
  about 
  2 
  feet 
  in 
  width, 
  there 
  comes 
  on 
  

   a 
  remarkable 
  conglomerate 
  which 
  occupies 
  the 
  foreshore 
  for 
  the 
  

   next 
  150 
  yards. 
  The 
  dip 
  of 
  this 
  bed 
  is 
  to 
  the 
  S.E. 
  at 
  45°, 
  that 
  

   is, 
  in 
  the 
  same 
  direction 
  and 
  at 
  the 
  same 
  angle 
  as 
  the 
  andesite 
  

   below 
  it, 
  and 
  this 
  fact, 
  together 
  with 
  the 
  absence 
  of 
  any 
  trace 
  of 
  

   crushing 
  in 
  either 
  rock 
  near 
  their 
  junction, 
  makes 
  it 
  practically 
  

   certain 
  that 
  the 
  conglomerate 
  is 
  not 
  faulted 
  against 
  the 
  andesite. 
  

  

  The 
  conglomerate 
  has 
  a 
  matrix 
  which 
  is 
  at 
  first 
  a 
  dark 
  ashy 
  

   shale, 
  including 
  many 
  angular 
  fragments, 
  of 
  various 
  sizes, 
  of 
  ash, 
  

   andesite, 
  and 
  shale; 
  and 
  here 
  and 
  there 
  small 
  veins 
  of 
  calcite 
  traverse 
  

   the 
  rock. 
  The 
  large 
  included 
  blocks 
  consist 
  mainly 
  of 
  limestone 
  or 
  

   ash, 
  very 
  few 
  pieces 
  of 
  grit 
  or 
  of 
  lava 
  being 
  seen 
  in 
  the 
  lower 
  

   portions 
  of 
  the 
  rock. 
  Several 
  varieties 
  of 
  limestone 
  occur 
  — 
  a 
  red, 
  

   somewhat 
  horny 
  type, 
  an 
  earthy 
  type, 
  crowded 
  with 
  fossils, 
  and 
  an 
  

   ashy 
  type. 
  The 
  ashes 
  are 
  mostly 
  of 
  a 
  calcareous 
  nature, 
  several 
  

   degrees 
  of 
  coarseness 
  being 
  represented. 
  These 
  larger 
  blocks 
  are 
  

   always 
  well 
  rounded, 
  and 
  are 
  most 
  of 
  them 
  from 
  6 
  to 
  9 
  inches 
  long. 
  

  

  Interbedded 
  with 
  the 
  conglomerate 
  there 
  occurs 
  at 
  one 
  point 
  a 
  

   thin 
  band 
  of 
  limestone, 
  and 
  a 
  few 
  feet 
  below 
  it 
  there 
  is 
  a 
  lenticular 
  

   mass 
  of 
  black 
  shale. 
  

  

  On 
  going 
  southward, 
  and 
  therefore 
  on 
  ascending 
  the 
  series, 
  

   the 
  matrix 
  of 
  the 
  conglomerate 
  is 
  seen 
  to 
  become 
  more 
  distinctly 
  

   ashy 
  and 
  yellowish 
  green 
  in 
  colour, 
  while 
  the 
  blocks 
  of 
  limestone 
  

   and 
  ash 
  first 
  decrease 
  in 
  number, 
  and 
  then 
  blocks 
  of 
  a 
  coarse 
  

   porphyrite 
  and 
  fine 
  andesites 
  become 
  numerous. 
  Occasionally 
  blocks 
  

   of 
  very 
  large 
  size 
  are 
  met 
  with 
  towards 
  the 
  centre 
  of 
  the 
  bed, 
  one 
  

   (of 
  ash) 
  measuring 
  5 
  feet 
  in 
  length. 
  

  

  About 
  150 
  yards 
  before 
  the 
  martello 
  tower 
  is 
  reached 
  there 
  

   occurs 
  on 
  the 
  foreshore 
  a 
  narrow 
  band 
  of 
  limestone 
  dipping 
  beneath 
  

   a 
  few 
  feet 
  of 
  black 
  shale, 
  the 
  latter 
  bed 
  containing 
  very 
  poorly- 
  

   preserved 
  graptolites, 
  identified 
  by 
  the 
  officers 
  of 
  the 
  Geological 
  

   Survey 
  as 
  Diplograptus 
  pristis. 
  Among 
  the 
  specimens 
  that 
  we 
  

   collected 
  Climacograptus 
  Scharenbergi 
  (Lapw.), 
  Diplograptus, 
  and 
  

   Dicellograptus 
  have 
  been 
  identified 
  for 
  us 
  by 
  Miss 
  E. 
  M. 
  R. 
  Wood. 
  

  

  The 
  strike 
  of 
  these 
  bands 
  appears 
  to 
  be 
  more 
  nearly 
  east 
  and 
  

   west 
  than 
  that 
  of 
  the 
  beds 
  to 
  the 
  north 
  ; 
  but 
  farther 
  out 
  to 
  sea 
  the 
  

   previous 
  north-easterly 
  and 
  south-westerly 
  strike 
  is 
  maintained, 
  and 
  

   certain 
  well-marked 
  bands 
  of 
  ash 
  are 
  clearly 
  traceable. 
  The 
  ashes 
  

   found 
  here 
  were 
  of 
  very 
  varied 
  types. 
  Some 
  were 
  fine, 
  some 
  coarse, 
  

   some 
  calcareous, 
  some 
  non- 
  calcareous. 
  Immediately 
  north 
  of 
  these 
  

   graptolitic 
  shales 
  the 
  officers 
  of 
  the 
  Geological 
  Survey 
  draw 
  a 
  fault 
  

   and 
  state 
  that 
  the 
  beds 
  are 
  there 
  reversed 
  in 
  their 
  dip, 
  but 
  we 
  

  

  