﻿114 
  C. 
  CALLAWAY 
  ON 
  THE 
  TORRIDON 
  SANDSTONE 
  IN 
  RELATION 
  

  

  11. 
  The 
  Toeeidon 
  Sandstone 
  in 
  relation 
  to 
  the 
  Ordovician 
  Rocks 
  

   of 
  the 
  Northern 
  Highlands. 
  By 
  C. 
  Callaway, 
  Esq., 
  M.A., 
  

   D.Sc. 
  Lond., 
  F.G.S. 
  (Read 
  December 
  21, 
  1881.) 
  

  

  The 
  late 
  Sir 
  R. 
  I, 
  Murchison 
  and 
  his 
  co-worker, 
  Prof. 
  A. 
  Geikie, 
  

   came 
  to 
  the 
  conclusion 
  that 
  the 
  Sutherland 
  quartzites 
  rested 
  uncon- 
  

   formably 
  upon 
  the 
  Torridon 
  Sandstone, 
  and 
  from 
  this 
  break 
  in 
  the 
  

   succession 
  they 
  inferred 
  that 
  the 
  latter 
  was 
  the 
  equivalent 
  of 
  the 
  

   Longmynd 
  or 
  Harlech 
  series, 
  the 
  Upper 
  Cambrian 
  being 
  wanting. 
  

   In 
  some 
  localities 
  the 
  sections, 
  seen 
  from 
  a 
  distance, 
  seem 
  to 
  con- 
  

   firm 
  their 
  opinion 
  ; 
  but 
  a 
  careful 
  and 
  detailed 
  examination 
  made 
  

   last 
  summer 
  convinced 
  me 
  that, 
  in 
  some 
  localities 
  at 
  least, 
  this 
  

   appearance 
  is 
  deceptive, 
  and 
  that 
  the 
  sandstone 
  passes 
  up 
  with 
  

   perfect 
  conformity 
  into 
  the 
  quartzite. 
  I 
  was 
  accompanied 
  during 
  

   my 
  work 
  by 
  Mr. 
  G. 
  H. 
  Bailey, 
  B.Sc, 
  of 
  Tettenhall 
  College, 
  to 
  

   whom 
  I 
  am 
  indebted 
  for 
  much 
  intelligent 
  and 
  active 
  assistance. 
  

  

  Loch 
  Broom. 
  

  

  Looking 
  up 
  at 
  the 
  section 
  from 
  the 
  road, 
  near 
  the 
  Ullapool 
  Hotel, 
  

   the 
  quartzite 
  is 
  seen 
  to 
  dip 
  east-north-east 
  at 
  15°, 
  while 
  the 
  Torridon 
  

   seems 
  to 
  lie 
  in 
  horizontal 
  beds. 
  This 
  appearance 
  of 
  the 
  latter 
  is 
  

   due 
  to 
  a 
  number 
  of 
  grooves, 
  many 
  of 
  them 
  horizontal, 
  which 
  cross 
  

   the 
  face 
  of 
  the 
  sandstone 
  cliff 
  and 
  suggest 
  bedding. 
  On 
  a 
  closer 
  

   investigation 
  the 
  true 
  stratification, 
  as 
  indicated 
  by 
  the 
  principal 
  

   pebble 
  bands, 
  is 
  found 
  to 
  be 
  conformable 
  to 
  the 
  overlying 
  quartzite. 
  

   Besides 
  this, 
  we 
  have 
  the 
  clearest 
  evidence 
  of 
  a 
  gradual 
  passage 
  

   between 
  the 
  two 
  groups. 
  The 
  Torridon, 
  which 
  is 
  mainly 
  made 
  up 
  

   of 
  quartz 
  and 
  felspar, 
  grows 
  more 
  quartzose 
  towards 
  the 
  top, 
  

   and 
  passes 
  into 
  the 
  basement 
  beds 
  of 
  the 
  quartzite, 
  which 
  contain 
  

   scattered 
  grains 
  of 
  felspar 
  and 
  graduate 
  upwards 
  into 
  pure 
  quart- 
  

   zite. 
  Some 
  of 
  the 
  passage 
  beds 
  are 
  of 
  so 
  intermediate 
  a 
  character 
  

   that 
  it 
  would 
  be 
  impossible 
  to 
  refer 
  hand 
  specimens 
  with 
  certainty 
  

   to 
  either 
  series. 
  

  

  Further 
  to 
  the 
  west, 
  in 
  the 
  quarries 
  above 
  the 
  village, 
  the 
  sand- 
  

   stone 
  is 
  well 
  exposed, 
  and, 
  though 
  the 
  stratification 
  is 
  much 
  obscured 
  

   by 
  current 
  lamination, 
  it 
  is 
  seen 
  to 
  be 
  in 
  conformity 
  with 
  the 
  

   quartzite. 
  

  

  Strath 
  Auchall. 
  

  

  The 
  junction 
  of 
  the 
  two 
  series 
  may 
  be 
  well 
  studied 
  on 
  the 
  north 
  

   side 
  of 
  the 
  valley 
  which 
  runs 
  up 
  from 
  Ullapool 
  to 
  Loch 
  Auchall. 
  

   The 
  sandstone 
  passes 
  under 
  the 
  quartzite 
  with 
  perfect 
  conformity, 
  

   the 
  dips 
  of 
  both 
  being 
  unmistakably 
  clear; 
  and 
  here 
  also 
  we 
  have 
  

   the 
  gradual 
  lithological 
  passage 
  seen 
  on 
  Loch 
  Broom. 
  But 
  this 
  

   section 
  furnishes 
  an 
  additional 
  proof 
  of 
  continuity. 
  Both 
  groups 
  

  

  