﻿162 
  T. 
  P. 
  JAHLESON 
  ON 
  THE 
  RED 
  CLAY 
  

  

  resulted 
  from 
  the 
  triturating 
  action 
  of 
  the 
  glacier-ice 
  passing 
  over 
  

   them. 
  The 
  red 
  clay 
  I 
  speak 
  of 
  looks 
  more 
  like 
  what 
  we 
  should 
  

   expect 
  to 
  find 
  in 
  a 
  district 
  of 
  Old 
  Red 
  Sandstone, 
  being 
  of 
  a 
  decided 
  

   brick-red 
  colour, 
  exactly 
  resembling 
  the 
  clay 
  we 
  find 
  in 
  the 
  Red-Sand- 
  

   stone 
  district 
  of 
  Kincardine 
  and 
  Forfar. 
  How 
  comes 
  it, 
  then, 
  that 
  a 
  

   red 
  clay 
  of 
  this 
  nature 
  should 
  be 
  found 
  stretching 
  so 
  far 
  over 
  a 
  tract 
  

   of 
  gneiss 
  and 
  granite 
  which 
  is 
  covered 
  by 
  grey 
  Boulder-clay 
  of 
  quite 
  

   a 
  different 
  hue 
  and 
  character 
  ? 
  For 
  this 
  red 
  clay 
  lies 
  on 
  the 
  top 
  of 
  the 
  

   grey 
  Boulder-clay, 
  and 
  has 
  therefore 
  been 
  laid 
  down 
  after 
  it. 
  The 
  

   grey 
  Boulder-clay 
  itself 
  seems 
  to 
  have 
  been 
  accumulated 
  beneath 
  a 
  

   sheet 
  of 
  ice 
  travelling 
  from 
  the 
  interior 
  of 
  the 
  country 
  towards 
  the 
  

   sea 
  ; 
  for 
  beneath 
  it 
  we 
  frequently 
  find 
  the 
  surface 
  of 
  the 
  rocks 
  worn 
  

   and 
  scratched 
  as 
  if 
  by 
  the 
  passage 
  of 
  a 
  glacier 
  coming 
  from 
  the 
  west- 
  

   ward, 
  while 
  the 
  boulders 
  and 
  stones 
  imbedded 
  in 
  it 
  are 
  such 
  as 
  

   would 
  be 
  furnished 
  by 
  the 
  rocks 
  that 
  occur 
  in 
  the 
  same 
  direction. 
  

  

  2. 
  Mineral 
  Contents 
  of 
  the 
  Red 
  Clay. 
  

  

  Now 
  the 
  Red 
  Clay 
  is 
  not 
  only 
  decidedly 
  different 
  in 
  colour, 
  but 
  is 
  

   further 
  distinguished 
  by 
  containing 
  stones 
  that 
  have 
  evidently 
  come 
  

   from 
  a 
  different 
  quarter. 
  Very 
  noticeable 
  among 
  these 
  are 
  certain 
  

   large 
  round 
  pebbles 
  of 
  grey 
  quartz 
  with 
  a 
  smooth 
  reddish 
  exterior, 
  

   such 
  as 
  are 
  met 
  with 
  in 
  the 
  Old 
  Red 
  Conglomerate 
  of 
  Kincardine- 
  

   shire. 
  They 
  vary 
  much 
  in 
  size 
  : 
  many 
  of 
  them 
  are 
  as 
  big 
  as 
  a 
  

   man's 
  head, 
  or 
  even 
  bigger 
  ; 
  and 
  they 
  occur 
  of 
  all 
  dimensions 
  below 
  

   that. 
  They 
  are 
  often 
  rubbed 
  and 
  scratched 
  as 
  if 
  by 
  the 
  action 
  of 
  

   ice, 
  and 
  frequently 
  worn 
  to 
  a 
  flat 
  sole 
  on 
  some 
  of 
  the 
  sides, 
  as 
  if 
  they 
  

   had 
  been 
  ground 
  down 
  by 
  long 
  rubbing 
  upon 
  a 
  hard 
  surface. 
  Their 
  

   mineral 
  character, 
  reddish 
  colour, 
  and 
  general 
  appearance 
  seem 
  to 
  

   show 
  that 
  they 
  have 
  come 
  out 
  of 
  the 
  Old 
  Red 
  Conglomerate 
  ; 
  but 
  

   there 
  is 
  another 
  feature 
  of 
  a 
  peculiar 
  kind 
  which 
  serves 
  still 
  more 
  

   certainly 
  to 
  identify 
  them. 
  In 
  the 
  Red 
  Conglomerate 
  rock 
  of 
  

   Kincardine 
  and 
  Forfar 
  many 
  of 
  these 
  pebbles 
  have 
  been 
  split, 
  frac- 
  

   tured, 
  and 
  recemented 
  while 
  imbedded 
  in 
  the 
  rock; 
  and 
  occasionally 
  

   they 
  are 
  indented 
  on 
  the 
  surface 
  by 
  the 
  pressure 
  of 
  an 
  adjoining 
  

   stone, 
  which 
  has 
  left 
  a 
  dint 
  or 
  depression 
  in 
  the 
  exterior 
  of 
  the 
  

   pebble, 
  while 
  here 
  and 
  there 
  one 
  may 
  be 
  seen 
  quite 
  distorted 
  in 
  

   shape, 
  owing 
  to 
  the 
  edges 
  of 
  the 
  split 
  pieces 
  being 
  shifted 
  a 
  little 
  

   past 
  each 
  other 
  as 
  if 
  by 
  a 
  fault 
  or 
  series 
  of 
  faults. 
  These 
  curious 
  

   pebbles 
  are 
  very 
  common 
  in 
  the 
  Conglomerate 
  near 
  Stonehaven 
  and 
  

   in 
  the 
  Garvock 
  hills, 
  and 
  were 
  noticed 
  long 
  ago 
  by 
  Mr. 
  Trevelyan. 
  

   (Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  i. 
  p. 
  147). 
  Now 
  many 
  of 
  the 
  quartz 
  

   pebbles 
  we 
  find 
  in 
  the 
  Red 
  Clay 
  of 
  Aberdeenshire 
  exhibit 
  all 
  these 
  

   features, 
  which 
  is 
  a 
  further 
  proof 
  that 
  they 
  have 
  been 
  derived 
  from 
  

   the 
  Conglomerate. 
  To 
  make 
  the 
  matter 
  still 
  more 
  sure, 
  we 
  find 
  in 
  

   some 
  places 
  fragments 
  of 
  the 
  red 
  sandstone 
  itself, 
  and 
  also, 
  more 
  

   rarely, 
  pieces 
  of 
  the 
  conglomerate. 
  

  

  These 
  reddish 
  quartz 
  pebbles 
  occur 
  all 
  over 
  the 
  area 
  covered 
  by 
  the 
  

   Red 
  Clay, 
  and 
  often 
  in 
  great 
  quantity. 
  They 
  are 
  very 
  common 
  in 
  the 
  

   parishes 
  of 
  Slains 
  and 
  Cruden, 
  especially 
  near 
  the 
  coast, 
  and 
  occur 
  

  

  