﻿116 
  C. 
  CALLAWAY 
  ON 
  THE 
  TORRIDON 
  SANDSTONE 
  IN 
  RELATION 
  

  

  In 
  this 
  district, 
  as 
  at 
  Ullapool, 
  the 
  quartzite 
  is 
  frequently 
  full 
  of 
  

   current-lamination. 
  The 
  persistence 
  through 
  the 
  two 
  series 
  of 
  the 
  

   same 
  conditions 
  of 
  deposit 
  adds 
  something 
  to 
  the 
  evidence 
  in 
  favour 
  

   of 
  their 
  conformity. 
  

  

  South 
  of 
  Unajpool. 
  

  

  A 
  few 
  miles 
  to 
  the 
  north 
  of 
  the 
  last 
  locality, 
  on 
  the 
  slope 
  above 
  

   TJnapool, 
  the 
  Torridon 
  Sandstone, 
  which 
  has 
  rapidly 
  thinned 
  out 
  to 
  

   a 
  few 
  score 
  feet, 
  dips 
  to 
  the 
  south-south-east 
  at 
  10°, 
  the 
  quartzite 
  

   overlying 
  it 
  with 
  perfect 
  conformity 
  and 
  containing 
  grains 
  of 
  the 
  

   usual 
  red 
  felspar 
  at 
  the 
  base. 
  

  

  Summctry 
  of 
  Evidence 
  for 
  the 
  Conformity. 
  

  

  In 
  every 
  section 
  examined 
  the 
  following 
  facts 
  were 
  observed 
  : 
  — 
  

  

  1. 
  Perfect 
  agreement 
  of 
  dip 
  between 
  the 
  sandstone 
  and 
  the 
  quart- 
  

   zite. 
  

  

  2. 
  A 
  gradual 
  lithological 
  passage 
  from 
  pure 
  quartzite 
  through 
  

   quartzo-felspathic 
  grit 
  into 
  ordinary 
  Torridon 
  Sandstone. 
  

  

  In 
  most 
  localities 
  it 
  was 
  also 
  noticed 
  that, 
  

  

  3. 
  Similar 
  conditions 
  of 
  deposit 
  prevailed 
  through 
  both 
  formations, 
  

   as 
  seen 
  in 
  the 
  frequent 
  presence 
  of 
  cross 
  lamination. 
  

  

  It 
  is 
  also 
  important 
  to 
  point 
  out 
  that, 
  

  

  4. 
  Change 
  of 
  dip 
  in 
  one 
  group 
  is, 
  so 
  far 
  as 
  these 
  observations 
  

   extended, 
  uniformly 
  accompanied 
  by 
  the 
  like 
  change 
  in 
  the 
  other. 
  

   Thus, 
  while 
  both 
  series 
  dip 
  to 
  the 
  east-north-east 
  in 
  the 
  Ullapool 
  and 
  

   Assynt 
  districts, 
  the 
  inclination 
  of 
  both 
  is 
  to 
  the 
  south-south-east 
  

   above 
  Unapool. 
  

  

  Age 
  of 
  the 
  Torridon 
  Sandstone. 
  

  

  If 
  I 
  am 
  justified 
  in 
  the 
  above 
  conclusion, 
  it 
  is 
  obvious 
  that 
  the 
  

   Lower 
  Cambrian 
  age 
  of 
  the 
  Torridon 
  can 
  no 
  longer 
  be 
  maintained. 
  

   It 
  is 
  generally 
  admitted 
  that 
  the 
  fossils 
  of 
  the 
  Durness 
  Limestone* 
  

   determine 
  the 
  Arenig 
  age 
  of 
  the 
  quartzo-calcareous 
  series. 
  The 
  

   Torridon 
  must 
  then 
  be 
  either 
  Upper 
  Cambrian 
  or 
  basement 
  Ordovi- 
  

   cian. 
  In 
  the 
  absence 
  of 
  fossils, 
  it 
  will 
  be 
  difficult 
  to 
  settle 
  the 
  

   question 
  ; 
  but 
  the 
  physical 
  evidence 
  seems 
  to 
  me 
  to 
  be 
  against 
  the 
  

   Cambrian 
  age. 
  For, 
  in 
  the 
  first 
  place, 
  both 
  the 
  Torridon 
  and 
  the 
  

   quartzite, 
  being 
  full 
  of 
  oblique 
  lamination, 
  must 
  have 
  been 
  quickly 
  

   accumulated. 
  The 
  rapid 
  thinning 
  out 
  of 
  the 
  former 
  and 
  the 
  fre- 
  

   quency 
  of 
  conglomerates 
  point 
  to 
  the 
  same 
  conclusion. 
  Besides 
  

   this, 
  it 
  will, 
  I 
  think, 
  be 
  found 
  necessary 
  to 
  reduce 
  the 
  usual 
  estimates 
  

   of 
  the 
  thickness 
  of 
  the 
  deposits. 
  On 
  Loch 
  Assynt, 
  the 
  Torridon 
  

   Sandstone 
  does 
  not 
  exceed 
  1000 
  feet, 
  most 
  of 
  which 
  must 
  have 
  been 
  

   rapidly 
  thrown 
  down. 
  Should 
  the 
  thickness 
  elsewhere 
  be 
  doubled 
  

  

  * 
  This 
  argument 
  takes 
  for 
  granted 
  the 
  generally 
  received 
  view 
  that 
  the 
  Dur 
  

   ness 
  and 
  Assynt 
  limestones 
  are 
  of 
  the 
  same 
  age. 
  This 
  is 
  denied 
  by 
  Prof. 
  Heddle 
  

   (Mineralogical 
  Magazine, 
  Aug. 
  1881).— 
  C. 
  C.> 
  Match 
  28, 
  1882, 
  

  

  