﻿TO 
  THE 
  ORDOVJCIAN 
  ROCKS 
  OP 
  THE 
  NORTHERN 
  HIGHLANDS. 
  115 
  

  

  display 
  very 
  distinct 
  current-lamination, 
  and 
  at 
  one 
  spot 
  the 
  

   lamination 
  (dipping 
  easterly 
  at 
  45°) 
  in 
  a 
  bed 
  forming* 
  the 
  base 
  of 
  the 
  

   quartzite 
  is 
  parallel 
  to 
  the 
  lamination 
  in 
  the 
  bed 
  of 
  sandstone 
  which 
  

   immediately 
  underlies 
  ; 
  so 
  that 
  it 
  would 
  appear 
  as 
  if 
  the 
  same 
  cur- 
  

   rent 
  which 
  threw 
  down 
  the 
  stratum 
  of 
  felspatho-quartzose 
  sand, 
  

   after 
  an 
  interval 
  deposited 
  the 
  bed 
  of 
  quartzose 
  sand. 
  

  

  Following 
  the 
  quartzite 
  up 
  the 
  valley, 
  we 
  come 
  to 
  an 
  abrupt 
  hollow 
  

   in 
  the 
  hillside, 
  and 
  on 
  the 
  opposite 
  slope 
  we 
  again 
  reach 
  the 
  Torridon, 
  

   thrown 
  up 
  by 
  a 
  fault, 
  and 
  the 
  conformable 
  upward 
  passage 
  into 
  

   quartzite 
  is 
  repeated. 
  

  

  Between 
  Ullapool 
  and 
  Strath 
  Kennort. 
  

  

  The 
  Torridon 
  Sandstone 
  is 
  well 
  seen 
  for 
  several 
  miles 
  along 
  the 
  

   road 
  from 
  Ullapool 
  to 
  the 
  north. 
  The 
  bedding 
  is 
  quite 
  distinct, 
  the 
  

   dip 
  still 
  being 
  steady 
  at 
  an 
  angle 
  of 
  from 
  10° 
  to 
  15°, 
  at 
  first 
  to 
  east- 
  

   north-east, 
  and 
  then, 
  towards 
  Strath 
  Kennort, 
  to 
  the 
  south-east. 
  

   Nowhere 
  did 
  we 
  observe 
  horizontal 
  stratification. 
  

  

  North 
  side 
  of 
  Loch 
  Assynt. 
  

  

  On 
  the 
  south 
  slope 
  of 
  Qneenaig 
  there 
  is, 
  as 
  at 
  Ullapool, 
  a 
  super- 
  

   ficial 
  appearance 
  of 
  unconformity, 
  which 
  vanishes 
  on 
  examina- 
  

   tion. 
  Towards 
  the 
  base 
  of 
  the 
  quartzite, 
  angular 
  bits 
  of 
  felspar 
  

   begin 
  to 
  come 
  in 
  abundantly, 
  and 
  the 
  rock 
  assumes 
  the 
  form 
  of 
  

   a 
  quartzo-felspathic 
  grit, 
  as 
  on 
  Loch 
  Broom. 
  We 
  first 
  worked 
  

   along 
  the 
  section 
  at 
  an 
  elevation 
  of 
  about 
  a 
  hundred 
  yards 
  

   above 
  the 
  road, 
  and 
  at 
  this 
  level 
  the 
  sandstone 
  for 
  some 
  distance 
  

   seemed 
  to 
  lie 
  horizontal 
  ; 
  but 
  as 
  the 
  rock 
  was 
  full 
  of 
  current 
  lami- 
  

   nation, 
  the 
  true 
  bedding 
  was 
  difficult 
  to 
  determine. 
  At 
  about 
  a 
  

   quarter 
  of 
  a 
  mile 
  to 
  the 
  west 
  of 
  the 
  junction, 
  the 
  obscurity 
  disap- 
  

   peared, 
  and 
  the 
  lower 
  part 
  of 
  the 
  Torridon, 
  consisting 
  of 
  flaggy 
  beds 
  

   and 
  more 
  aluminous 
  in 
  composition, 
  was 
  observed 
  to 
  dip 
  in 
  con- 
  

   formity 
  with 
  the 
  quartzite. 
  This 
  inclination 
  was 
  steadily 
  main- 
  

   tained 
  right 
  down 
  to 
  the 
  Lewisian 
  gneiss. 
  I 
  then 
  worked 
  back 
  

   towards 
  the 
  quartzite 
  at 
  the 
  level 
  of 
  the 
  road, 
  and, 
  when 
  possible, 
  

   on 
  the 
  shore 
  of 
  the 
  loch. 
  Along 
  this 
  line, 
  the 
  conformity 
  of 
  the 
  

   sandstone 
  to 
  the 
  quartzite 
  is 
  quite 
  clear. 
  The 
  appearance 
  of 
  horizon- 
  

   tality 
  at 
  the 
  higher 
  level 
  was 
  puzzling, 
  but 
  it 
  is 
  apparently 
  connected 
  

   with 
  current-lamination. 
  It 
  is 
  at 
  auy 
  rate 
  quite 
  certain 
  that 
  where 
  

   this 
  lamination 
  is 
  absent, 
  the 
  bedding 
  of 
  the 
  Torridon 
  is 
  distinctly 
  

   parallel 
  to 
  that 
  of 
  the 
  quartzite. 
  

  

  It 
  will 
  perhaps 
  help 
  to 
  explain 
  some 
  difficulties 
  to 
  observe 
  that 
  

   the 
  dip 
  of 
  the 
  rocks 
  gradually 
  decreases 
  as 
  we 
  descend 
  in 
  the 
  series. 
  

   The 
  usual 
  dip 
  of 
  the 
  upper 
  part 
  of 
  the 
  quartzite 
  is 
  15°, 
  which 
  

   towards 
  the 
  base 
  diminishes 
  to 
  10°. 
  The 
  underlying 
  Torridon 
  

   Sandstone 
  sometimes 
  reaches 
  10°. 
  It 
  is 
  usually 
  rather 
  lower^ 
  but 
  

   even 
  at 
  its 
  base 
  it 
  is 
  not 
  less 
  than 
  5°, 
  and 
  it 
  dips 
  throughout 
  in 
  the 
  

   same 
  direction 
  (east-north-east) 
  as 
  the 
  quartzite. 
  

  

  