﻿Vol. 
  S3] 
  

  

  THE 
  PORTRAJNE 
  INLIER 
  (C). 
  DUBLIN). 
  

  

  533 
  

  

  and 
  as 
  Priest's 
  Chamber 
  is 
  reiohed 
  the 
  rock 
  becomes 
  a 
  thrust- 
  

   conglomerate 
  formed 
  of 
  well-rounded 
  blocks 
  of 
  limestone 
  and 
  cal- 
  

   careous 
  ash 
  varying 
  greatly 
  in 
  size, 
  embedded 
  in 
  a 
  matrix 
  formed 
  of 
  

   fragments 
  of 
  the 
  same 
  material 
  and 
  of 
  crushed 
  shale 
  (see 
  fig. 
  3). 
  

   Some 
  of 
  the 
  blocks 
  of 
  ashy 
  limestone 
  contain 
  uncrushed 
  corals 
  and 
  

   brachiopoda, 
  and 
  sections 
  from 
  these 
  blocks 
  show 
  under 
  the 
  micro- 
  

   scope 
  no 
  straining 
  or 
  evidence 
  of 
  crushing. 
  

  

  Over 
  this 
  conglomerate 
  lie 
  the 
  grits 
  with 
  much-crushed 
  black 
  

   slates 
  at 
  their 
  base 
  (see 
  fig. 
  4). 
  

  

  Yig. 
  4. 
  — 
  Diagram 
  of 
  the 
  cliff 
  at 
  Priest's 
  Chamber, 
  looking 
  

   north-west. 
  

  

  Thrust 
  

   conglomerate 
  

  

  

  j9 
  

  

  It 
  is 
  an 
  interesting 
  fact 
  that, 
  both 
  at 
  this 
  point 
  and 
  at 
  others 
  where 
  

   the 
  disturbance 
  has 
  obviously 
  been 
  very 
  great, 
  sections 
  of 
  the 
  matrix, 
  

   as 
  well 
  as 
  sections 
  from 
  the 
  included 
  blocks, 
  show 
  very 
  little 
  sign 
  of 
  

   it. 
  At 
  Priest's 
  Chamber 
  the 
  matrix 
  is 
  seen 
  under 
  the 
  microscope 
  

   to 
  resemble, 
  on 
  the 
  whole, 
  the 
  ashy 
  limestone 
  exposed 
  inland 
  in 
  the 
  

   neighbourhood 
  of 
  the 
  Pigeon 
  House, 
  though 
  traces 
  of 
  crushing 
  are 
  

   to 
  be 
  seen, 
  and 
  sericite 
  is 
  occasionally 
  developed. 
  

  

  On 
  the 
  shore 
  south 
  of 
  St. 
  Kenny's 
  Well 
  there 
  is 
  a 
  larger 
  exposure 
  

   of 
  thrust-conglomerate, 
  but 
  no 
  cliff-section. 
  The 
  uppermost 
  beds 
  of 
  

   the 
  limestone 
  series 
  consist 
  here 
  of 
  calcareous 
  shales 
  passing 
  up 
  

   into 
  a 
  black 
  limestone 
  with 
  shaly 
  partings. 
  The 
  upper 
  bands 
  

   become 
  nodular, 
  and 
  the 
  series 
  dips 
  S.E. 
  at 
  about 
  30°. 
  Above 
  

   comes 
  a 
  bed 
  chiefly 
  composed 
  of 
  limestone-blocks 
  sometimes 
  a 
  foot 
  

   or 
  more 
  in 
  length, 
  and 
  usually 
  rounded 
  and 
  arranged 
  in 
  layers, 
  the 
  

   limestone 
  of 
  the 
  blocks 
  being 
  similar 
  to 
  that 
  of 
  the 
  underlying 
  

   beds. 
  

  

  The 
  matrix 
  in 
  which 
  these 
  blocks 
  are 
  embedded 
  is 
  sometimes 
  an 
  

   ordinary 
  black 
  shale, 
  showing 
  evidence 
  of 
  having 
  been 
  much 
  crushed, 
  

   and 
  forming 
  patches 
  quite 
  discontinuous 
  one 
  from 
  another 
  ; 
  but 
  

   more 
  often 
  it 
  is 
  a 
  crushed 
  limestone 
  or 
  a 
  crushed 
  calcareous 
  ash, 
  

   sometimes 
  containing 
  much 
  pyrites. 
  We 
  estimated 
  the 
  thickness 
  

  

  