﻿520 
  MESSES. 
  C. 
  I. 
  GARDINER 
  AND 
  S. 
  H. 
  REYNOLDS 
  ON 
  [Dec. 
  1 
  89 
  7, 
  

  

  35. 
  An 
  Account 
  of 
  the 
  Portraine 
  Inlier 
  (Co. 
  Dublin). 
  By 
  C. 
  I. 
  

   Gardiner, 
  Esq., 
  M.A., 
  F.G.S., 
  & 
  S. 
  H. 
  Reynolds, 
  Esq., 
  

   M.A., 
  F.G.S. 
  With 
  an 
  Appendix 
  on 
  the 
  Fossils 
  by 
  F. 
  E. 
  

   Cowper 
  Reed, 
  Esq., 
  M.A., 
  F.G.S. 
  (Read 
  June 
  9th, 
  1897.) 
  

  

  [Plates 
  XLII 
  & 
  XLIIL] 
  

  

  Contents. 
  

  

  Page 
  

  

  I. 
  Introduction 
  520 
  

  

  II. 
  Description 
  of 
  the 
  Area 
  and 
  its 
  Geological 
  Structure 
  521 
  

  

  III. 
  The 
  Igneous 
  and 
  Associated 
  Eocks 
  at 
  the 
  Northern 
  End 
  of 
  

  

  the 
  Inlier 
  521 
  

  

  IV. 
  The 
  Igneous 
  Rocks 
  at 
  the 
  Southern 
  End 
  of 
  the 
  Inlier 
  525 
  

  

  (a) 
  Those 
  exposed 
  along 
  the 
  Shore. 
  

  

  (b) 
  Those 
  exposed 
  Inland. 
  

  

  V. 
  The 
  Limestone 
  Series 
  527 
  

  

  (a) 
  The 
  Coast-section 
  North 
  of 
  the 
  Grrits. 
  

  

  (b) 
  The 
  Coast-section 
  South 
  of 
  the 
  Grits. 
  

  

  (c) 
  Exposures 
  Inland. 
  

  

  VI. 
  The 
  Grit 
  Series 
  531 
  

  

  VII. 
  The 
  Conglomerates 
  due 
  to 
  Earth-movements 
  531 
  

  

  VIII. 
  Summary 
  and 
  Conclusions 
  534 
  

  

  Appendix 
  on 
  the 
  Fossils 
  535 
  

  

  I. 
  Introduction. 
  

  

  The 
  coast 
  of 
  County 
  Dublin 
  is 
  well 
  known 
  for 
  the 
  variety 
  and 
  

   interest 
  of 
  the 
  rocks 
  exposed 
  along 
  it, 
  but 
  there 
  is 
  probably 
  no 
  part 
  

   of 
  it 
  more 
  interesting 
  than 
  that 
  in 
  the 
  neighbourhood 
  of 
  the 
  village 
  

   of 
  Portraine, 
  some 
  14 
  miles 
  north 
  of 
  Dublin 
  itself. 
  Here 
  occurs 
  

   an 
  inlier 
  of 
  pre-Devonian 
  rocks 
  which 
  prove 
  the 
  occurrence 
  in 
  

   the 
  district, 
  during 
  Bala 
  times, 
  of 
  much 
  volcanic 
  action 
  and 
  of 
  

   reef-building 
  corals. 
  The 
  interest 
  attaching 
  to 
  the 
  rocks 
  and 
  the 
  

   difficulty 
  of 
  interpreting 
  their 
  meaning 
  are 
  increased 
  by 
  the 
  great 
  

   amount 
  of 
  disturbance 
  which 
  has 
  gone 
  on 
  and 
  has 
  given 
  rise 
  to 
  

   extensive 
  developments 
  of 
  conglomerate-like 
  beds. 
  

  

  Volcanic 
  rocks, 
  which 
  are 
  certainly 
  of 
  the 
  same 
  age 
  as 
  those 
  at 
  

   Portraine, 
  and 
  coarse 
  conglomerates, 
  occur 
  on 
  Lambay 
  Island, 
  some 
  

   3 
  miles 
  out 
  to 
  sea, 
  and 
  we 
  hope 
  to 
  give 
  some 
  account 
  of 
  these 
  at 
  

   no 
  distant 
  date. 
  

  

  We 
  were 
  led 
  to 
  examine 
  the 
  beds 
  at 
  Portraine 
  from 
  a 
  wish 
  to 
  

   compare 
  them 
  with 
  the 
  Bala 
  Beds 
  occurring 
  in 
  the 
  neighbourhood 
  

   of 
  Kildare, 
  which 
  we 
  described 
  last 
  year. 
  1 
  

  

  The 
  Portraine 
  area 
  has, 
  perhaps, 
  hardly 
  received 
  so 
  much 
  attention 
  

   from 
  geologists 
  as 
  it 
  deserves. 
  The 
  first 
  description 
  is 
  that 
  given 
  by 
  

   H. 
  B. 
  Medlicott 
  2 
  ; 
  a 
  brief 
  account 
  is 
  given 
  by 
  G. 
  Y. 
  Du 
  JNoyer, 
  in 
  

   the 
  Memoirs 
  of 
  the 
  Irish 
  Geological 
  Survey, 
  the 
  memoir 
  including 
  

  

  1 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  Hi. 
  (1896) 
  p. 
  587. 
  

  

  2 
  Journ. 
  Geol. 
  Soc. 
  Dublin, 
  vol. 
  v. 
  (1853) 
  p. 
  265. 
  

  

  