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  XL— 
  Notes 
  on 
  the 
  Geology 
  of 
  the 
  Eildon 
  Hills, 
  in 
  Roxburghshire. 
  By 
  James 
  D. 
  

   Forbes, 
  Esq., 
  F.R.S., 
  Sec. 
  R.S. 
  Ed., 
  Professor 
  of 
  Natural 
  Philosophy 
  in 
  the 
  

   University 
  of 
  Edinburgh. 
  

  

  (Read 
  7th 
  April 
  1851.) 
  

  

  The 
  following 
  remarks, 
  being 
  the 
  result 
  of 
  a 
  careful 
  examination 
  of 
  a 
  small 
  

   district 
  of 
  country 
  characteristic 
  of 
  the 
  relations 
  of 
  the 
  trap 
  formations, 
  are 
  per- 
  

   haps 
  worthy 
  of 
  being 
  recorded 
  ; 
  although 
  the 
  general 
  features 
  of 
  the 
  county 
  of 
  

   Roxburgh 
  have 
  been 
  very 
  clearly 
  stated 
  in 
  a 
  paper 
  by 
  Mr 
  Milne, 
  published 
  in 
  

   the 
  15th 
  volume 
  of 
  the 
  Edinburgh 
  Transactions. 
  

  

  The 
  outburst 
  of 
  porphyritic 
  trap 
  forming 
  the 
  conspicuous 
  small 
  group 
  of 
  the 
  

   Eildon 
  Hills, 
  may 
  be 
  stated 
  to 
  be 
  surrounded 
  by 
  the 
  characteristic 
  greywacke 
  of 
  

   the 
  south 
  of 
  Scotland. 
  It 
  forms 
  an 
  elongated 
  patch 
  on 
  the 
  map, 
  extending 
  from 
  

   the 
  west 
  end 
  of 
  Bowden 
  Muir 
  in 
  the 
  direction 
  of 
  the 
  town 
  of 
  Selkirk, 
  and 
  running 
  

   from 
  west-south-west 
  to 
  east-north-east 
  (true) 
  towards 
  Bemerside 
  Hill, 
  on 
  the 
  north 
  

   bank 
  of 
  the 
  Tweed. 
  The 
  breadth 
  is 
  variable, 
  probably 
  less 
  than 
  is 
  generally 
  sup- 
  

   posed 
  ; 
  but 
  it 
  cannot 
  be 
  accurately 
  ascertained, 
  owing 
  to 
  the 
  accumulated 
  diluvium 
  

   which 
  covers 
  the 
  whole 
  south-eastern 
  slope 
  of 
  this 
  elevated 
  ridge. 
  On 
  this 
  ac- 
  

   count, 
  my 
  observations 
  on 
  the 
  contact 
  of 
  rocks 
  have 
  been 
  almost 
  entirely 
  confined 
  

   to 
  the 
  northern 
  and 
  western 
  boundaries 
  of 
  the 
  trap, 
  although 
  the 
  other 
  side 
  was 
  

   examined 
  with 
  equal 
  care. 
  

  

  The 
  character 
  of 
  the 
  greywacke 
  strata 
  near 
  Melrose 
  is 
  in 
  general 
  that 
  of 
  the 
  

   surrounding 
  country. 
  The 
  strike 
  is 
  nearly 
  due 
  east 
  and 
  west, 
  the 
  position 
  nearly 
  

   vertical, 
  rather 
  declining 
  to 
  the 
  north 
  ; 
  and 
  these 
  features 
  are 
  remarkably 
  uniform 
  

   and 
  uninterrupted. 
  In 
  the 
  excellent 
  sections 
  exhibited 
  by 
  the 
  course 
  of 
  the 
  rail- 
  

   way, 
  immediately 
  to 
  the 
  east 
  of 
  Melrose, 
  where 
  the 
  greywacke 
  is 
  not 
  far 
  distant 
  

   from 
  the 
  trap 
  of 
  the 
  Eildon 
  Hills, 
  the 
  strike 
  of 
  the 
  strata 
  inclines 
  more 
  to 
  the 
  

   south-west, 
  the 
  strata 
  are 
  thinner 
  and 
  more 
  undulating, 
  mixed 
  with 
  more 
  numer- 
  

   ous 
  clayey 
  strata, 
  and 
  including 
  many 
  veins 
  of 
  calcareous 
  spar. 
  If 
  we 
  follow 
  the 
  

   greywacke 
  strata 
  to 
  the 
  eastward, 
  we 
  find 
  them 
  exposed 
  near 
  the 
  village 
  of 
  New- 
  

   stead, 
  and 
  along 
  the 
  south 
  bank 
  of 
  the 
  Tweed 
  towards 
  Drygrange 
  Bridge. 
  Be- 
  

   tween 
  these 
  two 
  points 
  they 
  are 
  so 
  much 
  altered 
  as 
  to 
  be 
  scarcely 
  recognisable, 
  

   yet 
  having 
  the 
  usual 
  stratification 
  from 
  east 
  to 
  west. 
  There 
  is 
  every 
  appearance 
  

   of 
  a 
  real 
  barrier 
  having 
  crossed 
  the 
  present 
  course 
  of 
  the 
  river, 
  which 
  still 
  runs 
  

   in 
  a 
  very 
  uneven 
  channel 
  ; 
  and 
  behind 
  this 
  barrier 
  is 
  an 
  enormous 
  accumulation 
  

   of 
  debris 
  of 
  all 
  sorts, 
  forming 
  the 
  eminences 
  through 
  which 
  the 
  railway 
  passes, 
  

   beyond 
  the 
  village 
  of 
  Newstead, 
  which 
  have 
  no 
  nuclei 
  of 
  solid 
  rock, 
  as 
  far 
  as 
  can 
  

   be 
  seen. 
  Among 
  these 
  debris, 
  boulders 
  of 
  the 
  trap 
  tufa 
  of 
  Melrose 
  are 
  conspicu- 
  

  

  VOL. 
  XX. 
  PART 
  II. 
  3 
  L 
  

  

  