﻿150 
  T. 
  F. 
  JAMIESON 
  ON 
  THE 
  CRAG-SHELL 
  

  

  grey 
  sandstone 
  also 
  occur. 
  Taking 
  100 
  stones 
  at 
  random 
  from 
  a 
  pit 
  

   in 
  the 
  Kippet 
  ridge, 
  I 
  found 
  them 
  to 
  consist 
  of 
  

  

  Gneiss 
  and 
  mica-schist 
  68 
  

  

  Grey 
  and 
  yellow 
  limestone 
  20 
  

  

  Granite 
  7 
  

  

  Sandstone 
  3 
  

  

  Felspar 
  porphyry 
  2 
  

  

  100 
  

  

  In 
  addition 
  to 
  these, 
  fragments 
  of 
  greenstone 
  occur, 
  and 
  a 
  flint 
  

   may 
  now 
  and 
  then 
  be 
  found. 
  I 
  have 
  likewise 
  observed 
  a 
  few 
  pieces 
  

   of 
  serpentine. 
  

  

  The 
  Coast 
  Section. 
  (See 
  fig. 
  2.) 
  

  

  The 
  base 
  of 
  the 
  shelly 
  gravel 
  is 
  at 
  present 
  nowhere 
  displayed, 
  

   except 
  along 
  the 
  coast-line, 
  and 
  may 
  be 
  best 
  studied 
  between 
  

   Collieston 
  and 
  the 
  old 
  castle 
  of 
  Slains, 
  a 
  distance 
  of 
  little 
  more 
  than 
  a 
  

   mile. 
  Between 
  these 
  points 
  the 
  nature 
  of 
  the 
  section 
  is 
  as 
  follows 
  : 
  — 
  

   At 
  the 
  bottom 
  we 
  have 
  the 
  gneiss 
  or 
  mica-schist 
  (fig. 
  2, 
  a), 
  usually 
  

   forming 
  a 
  cliff 
  from 
  30 
  to 
  60 
  feet 
  high. 
  The 
  surface 
  of 
  the 
  rock, 
  so 
  

   far 
  as 
  I 
  have 
  seen, 
  is 
  not 
  smooth 
  and 
  glaciated, 
  but 
  is 
  commonly 
  of 
  a 
  

   worn 
  subangular 
  character, 
  occasionally 
  somewhat 
  fissured 
  and 
  dis- 
  

   integrated; 
  and 
  detached 
  pieces 
  of 
  the 
  rock 
  are 
  often 
  plentifully 
  

   mixed 
  with 
  the 
  overlying 
  bed. 
  Eesting 
  immediately 
  on 
  the 
  surface 
  of 
  

   the 
  rock 
  there 
  is 
  generally 
  a 
  stratum 
  of 
  grey 
  rubbish 
  (b), 
  usually 
  from 
  

   5 
  to 
  10 
  feet 
  thick, 
  which 
  sometimes 
  has 
  the 
  appearance 
  of 
  a 
  mass 
  of 
  

   disintegrated 
  gneiss, 
  like 
  that 
  beneath, 
  but 
  more 
  commonly 
  consists 
  

   of 
  small 
  pieces 
  of 
  gneiss 
  and 
  mica-schist, 
  with 
  some 
  pebbles 
  of 
  

   granite 
  and 
  now 
  and 
  then 
  a 
  boulder 
  of 
  greenstone, 
  packed 
  in 
  a 
  

   matrix 
  of 
  fine 
  debris 
  of 
  the 
  same 
  mineral 
  nature. 
  This 
  grey 
  stuff 
  is 
  

   more 
  loose 
  in 
  texture 
  than 
  the 
  Boulder-clay 
  usually 
  is, 
  and 
  not 
  so 
  

   hard, 
  tough, 
  and 
  impenetrable. 
  The 
  reason 
  appears 
  to 
  be 
  that 
  it 
  

   contains 
  less 
  clay 
  or 
  fine 
  muddy 
  sediment; 
  and 
  perhaps 
  also 
  

   it 
  has 
  undergone 
  less 
  compression. 
  In 
  one 
  or 
  two 
  places 
  to 
  the 
  

   north 
  of 
  Collieston, 
  it 
  contains 
  broken 
  pieces 
  of 
  the 
  Crag 
  shells 
  and 
  

   bits 
  of 
  the 
  limestone 
  mixed 
  through 
  it 
  ; 
  but 
  this 
  is 
  so 
  exceptional 
  

   that 
  it 
  may 
  be 
  owing 
  to 
  accident. 
  No 
  glacial 
  markings 
  have 
  been 
  

   observed 
  by 
  me 
  on 
  any 
  of 
  the 
  stones 
  in 
  this 
  grey 
  stuff 
  at 
  the 
  base 
  of 
  

   the 
  section 
  between 
  Collieston 
  and 
  the 
  old 
  castle 
  ; 
  but 
  ice-scratched 
  

   stones 
  do 
  occur, 
  although 
  not 
  very 
  commonly, 
  in 
  what 
  appears 
  to 
  be 
  

   the 
  same 
  bed, 
  to 
  the 
  north 
  and 
  south 
  of 
  these 
  points, 
  while 
  the 
  

   character 
  of 
  the 
  stuff 
  assimilates 
  more 
  to 
  the 
  nature 
  of 
  an 
  ordinary 
  

   Boulder-clay, 
  I 
  therefore 
  think 
  that 
  this 
  stratum 
  of 
  grey 
  rubbish, 
  

   which 
  is 
  very 
  uniformly 
  present 
  along 
  the 
  coast 
  of 
  Slains 
  and 
  

   Cruden, 
  covering 
  the 
  surface 
  of 
  the 
  rock 
  to 
  a 
  depth 
  of 
  from 
  5 
  to 
  

   10 
  feet, 
  must 
  be 
  a 
  deposit 
  of 
  the 
  glacial 
  period, 
  and 
  has 
  probably 
  

   been 
  the 
  result 
  of 
  a 
  sheet 
  of 
  land-ice 
  acting 
  on 
  the 
  surface 
  of 
  the 
  

   country. 
  

  

  