﻿V°l* 
  53-] 
  ANNIVERSARY 
  ADDRESS 
  OE 
  THE 
  PRESIDENT. 
  lxxxvii 
  

  

  of 
  several 
  thousand 
  feet 
  in 
  the 
  neighbourhood 
  of 
  Loch 
  Maree 
  and 
  

   Loch 
  Torridon 
  in 
  Koss-shire, 
  was 
  until 
  then 
  generally 
  classed 
  as 
  of 
  

   Cambrian 
  age 
  ; 
  therefore 
  this 
  discovery 
  of 
  the 
  Olenellus-zone 
  in 
  the 
  

   overlying 
  rocks 
  at 
  once 
  made 
  it 
  clear 
  that 
  the 
  Torridon 
  Sandstone 
  

   would 
  in 
  future 
  have 
  to 
  be 
  classed 
  as 
  of 
  pre-Cambrian 
  age. 
  It 
  had 
  

   been 
  known 
  for 
  a 
  long 
  period 
  that 
  the 
  Torridon 
  Sandstone 
  rested 
  on 
  

   a 
  strongly-eroded 
  surface 
  of 
  Archcean 
  gneiss 
  and 
  schists, 
  fragments 
  

   of 
  which 
  occurred 
  in 
  it, 
  and 
  in 
  the 
  year 
  1878 
  (Quart. 
  Journ. 
  Geol. 
  

   Soc. 
  vol. 
  xxxiv. 
  p. 
  813) 
  I 
  particularly 
  called 
  attention 
  to 
  the 
  fact 
  that 
  

   in 
  addition 
  to 
  these 
  local 
  fragments 
  there 
  were 
  others, 
  especially 
  in 
  

   the 
  basal 
  breccias 
  at 
  Gairloch, 
  which 
  did 
  not 
  seem 
  ' 
  to 
  have 
  come 
  

   from 
  the 
  immediate 
  neighbourhood/ 
  but 
  were 
  ' 
  similar 
  in 
  many 
  

   respects 
  to 
  those 
  found 
  in 
  the 
  Cambrian 
  conglomerates 
  in 
  Wales, 
  

   and 
  which 
  were 
  there 
  undoubtedly 
  derived 
  from 
  the 
  underlying 
  

   Pebidian 
  beds.' 
  1 
  In 
  the 
  more 
  recent 
  descriptions 
  given 
  by 
  the 
  

   Geological 
  Surveyors 
  of 
  the 
  Torridon 
  Sandstone 
  in 
  the 
  different 
  

   areas 
  attention 
  is 
  also 
  pointedly 
  called 
  to 
  these 
  facts, 
  and 
  it 
  

   seems 
  highly 
  probable 
  that 
  at 
  one 
  time 
  a 
  volcanic 
  group 
  of 
  rocks 
  

   similar 
  to 
  the 
  Pebidian 
  of 
  Wales 
  must 
  have 
  existed 
  either 
  in 
  the 
  

   area 
  or 
  at 
  no 
  great 
  distance 
  from 
  it. 
  In 
  that 
  case 
  the 
  volcanic 
  

   group 
  would 
  have 
  to 
  be 
  classed 
  as 
  older 
  than 
  the 
  Torridonian 
  and 
  

   newer 
  than 
  the 
  gneiss 
  and 
  crystalline 
  schists, 
  as 
  in 
  Wales. 
  The 
  

   Longmyndian 
  and 
  Torridonian 
  rocks 
  seem 
  therefore 
  to 
  be 
  nearly 
  on 
  

   the 
  same 
  horizon, 
  and 
  intermediate 
  in 
  position 
  between 
  the 
  Pebidian 
  

   and 
  the 
  Cambrian. 
  In 
  referring 
  to 
  the 
  Torridonian 
  rocks 
  in 
  

   the 
  ' 
  Annual 
  Report 
  of 
  the 
  Geological 
  Survey 
  ' 
  for 
  1895, 
  p. 
  20, 
  

   Sir 
  A. 
  Geikie 
  says 
  : 
  — 
  ' 
  During 
  the 
  progress 
  of 
  the 
  mapping 
  of 
  the 
  

   Torridonian 
  rocks 
  in 
  the 
  west 
  of 
  Sutherland 
  and 
  Boss-shire, 
  the 
  

   attention 
  of 
  the 
  surveyors 
  has 
  been 
  continually 
  directed 
  to 
  the 
  

   nature 
  of 
  the 
  sediments 
  composing 
  these 
  rocks, 
  and 
  to 
  the 
  inter- 
  

   esting 
  problems 
  connected 
  with 
  their 
  origin. 
  W 
  r 
  hile 
  the 
  sandstones, 
  

   shales, 
  and 
  conglomerates 
  of 
  this 
  system 
  may 
  be 
  reasonably 
  supposed 
  

   to 
  have 
  been 
  mainly 
  derived 
  from 
  the 
  denudation 
  of 
  the 
  Lewisian 
  

   Gneiss, 
  they 
  yet 
  contain 
  materials 
  which 
  have 
  not 
  been 
  found 
  in 
  

   the 
  gneiss 
  itself, 
  and 
  the 
  source 
  of 
  which 
  it 
  would 
  be 
  important, 
  if 
  

   possible, 
  to 
  discover. 
  The 
  contents 
  of 
  the 
  conglomerates 
  seem 
  to 
  

   prove 
  the 
  existence 
  of 
  some 
  series 
  of 
  sedimentary 
  and 
  volcanic 
  

   rocks 
  older 
  than 
  the 
  Torridonian 
  formations. 
  It 
  seemed 
  desirable 
  

   that 
  a 
  detailed 
  study 
  should 
  be 
  made 
  of 
  the 
  Torridonian 
  petrography. 
  

  

  1 
  In 
  1880, 
  Proc. 
  Geol. 
  Assoc, 
  I 
  mentioned 
  the 
  following 
  as 
  occurrirg 
  as 
  

   fragments, 
  namely, 
  gneiss, 
  granite, 
  quartz-felsite, 
  quartz-quartzite, 
  jasper, 
  taJcose, 
  

   ehloritic 
  and 
  micaceous 
  schistose 
  rocks, 
  etc. 
  See 
  also 
  ' 
  Pre-Cambrian 
  Eocis 
  in 
  

   Cambrian 
  Conglomerates,' 
  Geol. 
  Mag. 
  1890, 
  p. 
  516. 
  

  

  vcl 
  liii. 
  g 
  

  

  