﻿OF 
  THE 
  EILDON 
  HILLS, 
  IN 
  ROXBURGHSHIRE. 
  215 
  

  

  ably 
  very 
  near 
  the 
  mass 
  of 
  Bowden 
  trap. 
  The 
  purple 
  and 
  yellow 
  trap-dyke 
  may 
  

   probably 
  be 
  identified 
  also 
  with 
  one 
  (No. 
  29) 
  cutting 
  the 
  new 
  red 
  sandstone 
  in 
  

   the 
  " 
  Duke's 
  Glen," 
  behind 
  the 
  Quarry 
  Hill 
  at 
  Melrose, 
  already 
  referred 
  to. 
  

  

  I 
  shall 
  conclude 
  with 
  some 
  observations 
  on 
  the 
  structure 
  of 
  the 
  Eildon 
  Hills 
  

   themselves. 
  We 
  have 
  seen 
  that 
  the 
  grey 
  wacke 
  formation 
  rises 
  to 
  within 
  200 
  feet 
  

   or 
  thereabouts 
  of 
  the 
  level 
  of 
  the 
  col 
  or 
  neck 
  which 
  unites 
  the 
  two 
  principal 
  emi- 
  

   nences. 
  At 
  this 
  very 
  level 
  occurs 
  a 
  tolerably 
  marked 
  shelf 
  of 
  diluvium, 
  which 
  has 
  

   strongly 
  the 
  appearance 
  of 
  having 
  been 
  caused 
  by 
  a 
  temporary 
  sojourn 
  of 
  stag- 
  

   nant 
  water 
  at 
  that 
  height. 
  Mr 
  Milne 
  has 
  very 
  correctly 
  remarked, 
  that 
  the 
  drift 
  

   on 
  the 
  Eildon 
  Hills 
  includes 
  fragments 
  of 
  bright 
  red 
  sandstone. 
  This 
  phenome- 
  

   non 
  is 
  better 
  marked, 
  however, 
  on 
  the 
  south 
  side 
  of 
  the 
  col 
  or 
  neck 
  above 
  referred 
  

   to. 
  It 
  is 
  an 
  inquiry 
  of 
  some 
  interest 
  whence 
  these 
  fragments 
  could 
  possibly 
  have 
  

   been 
  derived 
  so 
  as 
  to 
  have 
  been 
  transported 
  by 
  water 
  or 
  otherwise 
  to 
  so 
  high 
  a 
  

   level. 
  The 
  last 
  visible 
  grey 
  wacke 
  strata 
  (at 
  5 
  or 
  6) 
  are 
  not 
  much 
  altered 
  (whilst 
  

   nearer 
  the 
  farm 
  of 
  Dingleton 
  the 
  alteration 
  is 
  very 
  marked, 
  the 
  strata 
  being 
  iron- 
  

   shot 
  and 
  hardened, 
  and 
  the 
  direction 
  of 
  strike 
  in 
  some 
  places 
  changed). 
  Here 
  the 
  

   rock 
  is 
  sandy 
  and 
  of 
  natural 
  hardness, 
  the 
  strata 
  nearly 
  vertical, 
  and 
  running 
  

   almost 
  due 
  east 
  and 
  west 
  ; 
  in 
  short, 
  in 
  almost 
  exact 
  parallelism 
  to 
  the 
  general 
  

   stratification 
  of 
  the 
  country. 
  Yet 
  this 
  must 
  be 
  very 
  close 
  to 
  the 
  contact 
  with 
  

   the 
  great 
  mass 
  of 
  porphyry 
  of 
  the 
  Eildons, 
  though 
  the 
  junction 
  can 
  no 
  where 
  be 
  

   perceived. 
  In 
  ascending 
  slopingly 
  to 
  the 
  top 
  of 
  the 
  highest 
  Eildon 
  by 
  its 
  north- 
  

   west 
  acclivity, 
  I 
  found 
  many 
  blocks, 
  apparently 
  of 
  altered 
  greywacke, 
  having 
  a 
  

   singular 
  character, 
  some 
  quite 
  injected 
  (as 
  it 
  appeared 
  to 
  me) 
  with 
  felspar, 
  yet 
  

   distinguishable 
  almost 
  by 
  the 
  touch 
  from 
  felspar 
  rock, 
  having 
  a 
  peculiar 
  gritty 
  

   feel. 
  These 
  blocks 
  appeared 
  to 
  have 
  fallen 
  from 
  small 
  cliffs 
  above, 
  which, 
  having 
  

   ascended, 
  I 
  found 
  to 
  display 
  a 
  progressive 
  alteration 
  or 
  metamorphosis 
  from 
  the 
  

   trap 
  rock 
  of 
  the 
  hill 
  into 
  a 
  rock 
  having 
  in 
  one 
  place 
  almost 
  the 
  character 
  of 
  

   gneiss, 
  and 
  which 
  I 
  take 
  to 
  be 
  a 
  portion 
  of 
  indurated 
  greywacke 
  caught 
  up 
  by 
  the 
  

   trap, 
  and 
  forming 
  the 
  greater 
  part 
  of 
  the 
  summit 
  of 
  the 
  Eildon, 
  whose 
  bold 
  form 
  

   arises 
  in 
  part 
  from 
  the 
  excessive 
  resistance 
  of 
  such 
  metamorphic 
  rocks 
  to 
  the 
  

   action 
  of 
  the 
  weather. 
  The 
  real 
  trap 
  which 
  has 
  effected 
  this 
  metamorphosis 
  is 
  a 
  

   porphyritic 
  claystone, 
  and 
  the 
  whole 
  somewhat 
  resembles 
  the 
  well-known 
  features 
  

   of 
  the 
  geology 
  of 
  the 
  Pentland 
  Hills 
  at 
  Habbie's 
  How.* 
  

  

  Repeated 
  visits 
  and 
  a 
  careful 
  selection 
  of 
  specimens 
  confirmed 
  this 
  view. 
  

   Specimens 
  of 
  the 
  brick-red 
  felspar 
  passing 
  into 
  claystone 
  porphyry 
  are 
  found 
  in 
  

   Nos. 
  7, 
  11, 
  15. 
  As 
  we 
  approach 
  the 
  top 
  it 
  becomes 
  slaty, 
  and 
  the 
  direction 
  of 
  

   cleavage 
  shifts 
  round, 
  dipping 
  towards 
  the 
  centre 
  of 
  the 
  cone, 
  the 
  summit 
  being 
  

   , 
  what 
  appeared 
  to 
  me 
  the 
  altered 
  rock. 
  The 
  slaty 
  felspar 
  acquires 
  green 
  dots 
  

   (Nos. 
  8 
  and 
  9.) 
  Then 
  we 
  have 
  the 
  slaty 
  rock 
  shot 
  with 
  red 
  felspar 
  (12), 
  before 
  

  

  * 
  Mr 
  Milne 
  describes 
  the 
  top 
  of 
  Eildon 
  as 
  composed 
  of 
  a 
  very 
  hard 
  clinkstone 
  with 
  a 
  grey 
  

   basis, 
  which 
  strikes 
  fire 
  with 
  steel. 
  But 
  true 
  clinkstone 
  could 
  not 
  do 
  so, 
  being 
  a 
  pure 
  felspar. 
  

  

  VOL. 
  XX. 
  PART 
  II. 
  3 
  M 
  

  

  