﻿Vol. 
  53.] 
  ANNIVERSARY 
  ADDRESS 
  OF 
  THE 
  PRESIDENT. 
  lxxix 
  

  

  it 
  became 
  cemented 
  in 
  the 
  mass. 
  This 
  appearance 
  as 
  if 
  of 
  a 
  gradual 
  

   passage 
  from 
  conglomerates 
  to 
  rocks 
  below, 
  and 
  from 
  which 
  most 
  of 
  

   their 
  materials 
  must 
  have 
  been 
  derived, 
  has 
  often 
  presented 
  itself 
  to 
  

   my 
  mind 
  in 
  examining 
  these 
  basal 
  lines 
  of 
  the 
  pre-Cambrian 
  rocks.' 
  l 
  

   In 
  Caernarvonshire, 
  Upper, 
  Middle, 
  and 
  traces 
  of 
  Lower 
  Cambrian 
  

   fossils 
  have 
  been 
  discovered, 
  the 
  latter 
  mainly 
  at 
  the 
  Penrhyn 
  slate- 
  

   quarry, 
  near 
  Bethesda. 
  It 
  is 
  unfortunate 
  that 
  these 
  have 
  not 
  as 
  

   yet 
  been 
  fully 
  worked 
  out, 
  but 
  that 
  there 
  are 
  zones 
  of 
  fossils 
  below 
  

   the 
  beds 
  containing 
  Conocoryphe 
  Viola 
  described 
  by 
  Dr. 
  Woodward 
  

   seemed 
  to 
  me, 
  when 
  I 
  last 
  examined 
  the 
  section, 
  quite 
  clear. 
  The 
  

   sections 
  of 
  Cambrian 
  rocks 
  in 
  this 
  area 
  agree 
  remarkably 
  with 
  those 
  

   found 
  in 
  Pembrokeshire, 
  and 
  I 
  have 
  no 
  doubt 
  that 
  the 
  underlying 
  

   Cambrian 
  conglomerates 
  rest 
  here 
  also 
  on 
  an 
  eroded 
  surface 
  of 
  

   pre-Cambrian 
  rocks. 
  

  

  Ant 
  

  

  Until 
  the 
  year 
  1878 
  it 
  was 
  not 
  suspected 
  that 
  the 
  granite 
  and 
  

   gneiss-rocks 
  in 
  Central 
  Anglesey 
  were 
  of 
  pre-Cambrian 
  age, 
  but 
  in 
  

   that 
  year, 
  after 
  visiting 
  the 
  area, 
  I 
  read 
  a 
  paper 
  at 
  the 
  British 
  Associ- 
  

   ation 
  in 
  which 
  I 
  claimed 
  the 
  so-called 
  intrusive 
  granite 
  in 
  Central 
  

   Anglesey 
  and 
  the 
  associated 
  gneiss, 
  as 
  well 
  as 
  the 
  whole 
  of 
  the 
  area 
  

   marked 
  as 
  altered 
  Cambrian 
  in 
  that 
  island, 
  as 
  of 
  pre-Cambrian 
  age. 
  

   I 
  stated 
  that 
  the 
  granitoid 
  and 
  gneissose 
  rocks 
  were 
  at 
  the 
  base, 
  and 
  

   that, 
  as 
  at 
  St. 
  David's, 
  they 
  were 
  succeeded 
  by 
  the 
  agglomerates, 
  

   breccias, 
  greenstone-bands, 
  and 
  schists 
  of 
  the 
  Pebidian 
  group. 
  In 
  

   the 
  Memoirs 
  of 
  the 
  Geological 
  Survey 
  published 
  in 
  1881, 
  the 
  view 
  that 
  

   the 
  granite 
  was 
  intrusive 
  in 
  Cambrian 
  and 
  Silurian 
  rocks, 
  and 
  

   that 
  the 
  latter 
  had 
  been 
  metamorphosed 
  into 
  gneiss, 
  schists, 
  etc., 
  was 
  

   still 
  upheld. 
  The 
  pre-Cambrian 
  rocks 
  of 
  Anglesey 
  have 
  since 
  been 
  

   described 
  by 
  Prof. 
  Hughes, 
  Prof. 
  Bonney, 
  Dr. 
  Callaway, 
  Mr. 
  Blake, 
  

   and 
  others, 
  and 
  it 
  is 
  now 
  fully 
  admitted 
  that 
  the 
  views 
  which 
  

   we 
  advanced 
  in 
  1878 
  are 
  in 
  the 
  main 
  correct. 
  In 
  his 
  Address 
  to 
  

   this 
  Society 
  in 
  1891, 
  Sir 
  A. 
  Geikie 
  says 
  : 
  — 
  ' 
  Let 
  me 
  frankly 
  say 
  

   at 
  once 
  that 
  in 
  denying 
  the 
  existence 
  of 
  pre-Cambrian 
  rocks 
  in 
  

   Anglesey, 
  and 
  in 
  endeavouring 
  to 
  account 
  for 
  all 
  the 
  schists 
  by 
  the 
  

   metamorphism 
  of 
  Cambrian 
  and 
  Silurian 
  strata, 
  my 
  predecessor 
  

   was, 
  in 
  my 
  opinion, 
  mistaken 
  ' 
  2 
  ; 
  and 
  again 
  : 
  ' 
  There 
  is 
  un- 
  

   doubtedly 
  in 
  Central 
  Anglesey 
  a 
  core 
  of 
  gneiss 
  which, 
  if 
  petro- 
  

   graphical 
  characters 
  may 
  be 
  taken 
  as 
  a 
  guide, 
  must 
  certainly 
  be 
  

   looked 
  upon 
  as 
  Archaean.' 
  Here 
  he 
  refers 
  to 
  the 
  so-called 
  axis 
  

  

  1 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxxiv. 
  (1878) 
  p. 
  151. 
  

  

  2 
  Ibid. 
  vol. 
  xlvii. 
  (1891) 
  Proc. 
  pp. 
  82, 
  83. 
  

  

  