﻿lxxxviii 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [May 
  1 
  897, 
  

  

  Accordingly 
  I 
  requested 
  Mr. 
  Teall 
  to 
  undertake 
  this 
  task. 
  He 
  

   has 
  already 
  made 
  considerable 
  progress 
  in 
  the 
  investigation, 
  

   directing 
  special 
  attention 
  to 
  those 
  pebbles 
  in 
  the 
  conglomerates 
  

   which 
  were 
  evidently 
  not 
  derived 
  from 
  the 
  immediately 
  underlying 
  

   gneiss. 
  The 
  specimens 
  collected 
  in 
  the 
  field 
  and 
  submitted 
  to 
  him 
  

   comprise 
  vein-quartz, 
  quartzites, 
  cherts, 
  jasper, 
  felsites, 
  quartz- 
  

   schists, 
  and 
  mica-schist, 
  including 
  green 
  avanturine.' 
  And 
  at 
  

   page 
  21 
  (Notes 
  by 
  Mr. 
  Teall) 
  : 
  — 
  ' 
  The 
  felsites 
  are 
  exceptionally 
  

   interesting, 
  and 
  have 
  been 
  described 
  in 
  detail. 
  They 
  are 
  dark- 
  

   purplish 
  compact 
  rocks, 
  usually 
  less 
  red 
  in 
  colour 
  than 
  the 
  jaspers, 
  

   but 
  not 
  always 
  easily 
  distinguishable 
  from 
  them. 
  They 
  consist 
  of 
  

   porphyritic 
  crystals, 
  and 
  crystal-groups 
  of 
  felspar, 
  often 
  oligoclase, 
  

   in 
  a 
  spherulitic, 
  micropegrnatitic, 
  micropoikilitic, 
  or 
  microcrystal- 
  

   line 
  groundmass. 
  The 
  spherulitic 
  felsites 
  occasionally 
  show 
  traces 
  

   of 
  perlitic 
  structure 
  in 
  the 
  matter 
  which 
  fills 
  up 
  the 
  spaces 
  between 
  

   the 
  spherulites. 
  These 
  felsites 
  bear 
  the 
  most 
  striking 
  resemblance 
  

   to 
  those 
  of 
  Uriconian 
  age 
  which 
  occur 
  in 
  Shropshire, 
  and 
  which 
  

   have 
  furnished 
  pebbles 
  to 
  some 
  portions 
  of 
  the 
  Longmyndian 
  rocks/ 
  

   It 
  is 
  also 
  stated 
  that 
  ' 
  the 
  tracts 
  of 
  Torridonian 
  rocks 
  mapped 
  last 
  

   year 
  have 
  lain 
  entirely 
  to 
  the 
  east 
  of 
  the 
  line 
  of 
  great 
  complication, 
  

   and 
  are 
  all 
  moved 
  masses.' 
  In 
  my 
  paper, 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  

   vol. 
  xxxix. 
  (1883), 
  I 
  called 
  attention 
  to 
  the 
  fact 
  that 
  we 
  had 
  found 
  

   these 
  rocks 
  in 
  several 
  localities 
  east 
  of 
  the 
  limit 
  usually 
  assigned 
  to 
  

   them, 
  including 
  most 
  of 
  the 
  areas 
  referred 
  to 
  in 
  the 
  report, 
  and 
  

   said, 
  p. 
  148 
  : 
  — 
  ' 
  That 
  these 
  are 
  true 
  Torridon 
  Sandstones, 
  and 
  not 
  

   subordinate 
  bands 
  in 
  the 
  quartzite 
  series, 
  is 
  perfectly 
  clear 
  to 
  any- 
  

   one 
  who 
  has 
  seen 
  the 
  succession 
  on 
  the 
  Torridon 
  shores.' 
  

  

  Recent 
  researches 
  by 
  the 
  Geological 
  Surveyors 
  and 
  others 
  have 
  

   tended 
  strongly 
  to 
  confirm 
  the 
  view 
  that 
  the 
  gneisses 
  and 
  crystal- 
  

   line 
  schists 
  in 
  the 
  central 
  areas 
  in 
  Ross 
  and 
  Sutherland, 
  as 
  also 
  in 
  

   the 
  Central 
  Highlands, 
  are 
  of 
  pre-Cambrian 
  age, 
  but 
  the 
  exact 
  age 
  

   of 
  some 
  newer 
  rocks 
  which 
  overlie 
  or 
  are 
  entangled 
  amongst 
  them 
  

   has 
  not 
  as 
  yet 
  been 
  made 
  out. 
  It 
  is 
  probable 
  that 
  in 
  time 
  some 
  of 
  

   these 
  will 
  be 
  shown 
  to 
  be 
  of 
  Cambrian 
  age. 
  

  

  South 
  of 
  England 
  and 
  Channel 
  Islands. 
  

  

  Having 
  thus 
  referred 
  to 
  the 
  areas 
  in 
  Wales, 
  the 
  centre 
  of 
  

   England, 
  and 
  North 
  Britain, 
  where 
  the 
  facts 
  are 
  clear, 
  it 
  may 
  now 
  

   be 
  well 
  to 
  enquire 
  into 
  the 
  evidence 
  which 
  has 
  been 
  brought 
  

   forward 
  to 
  show 
  the 
  presence 
  of 
  pre-Cambrian 
  rocks 
  in 
  more 
  

   southerly 
  districts. 
  In 
  my 
  paper 
  ' 
  On 
  some 
  Recent 
  Researches 
  

   among 
  Pre-Cambrian 
  Rocks 
  in 
  the 
  British 
  Isles' 
  (Proc. 
  Geol. 
  

  

  