﻿54 
  THEOBALD 
  \ 
  GEOLOGY 
  OF 
  PEGU. 
  

  

  being 
  from 
  6 
  to 
  9 
  inches 
  across, 
  mixed 
  of 
  course 
  with 
  smaller 
  sized 
  ones 
  

   and 
  pebbles, 
  in 
  a 
  somewhat 
  irregular 
  fashion. 
  

  

  These 
  coarser 
  beds 
  at 
  once 
  suggest 
  two 
  questions, 
  viz., 
  whence 
  

   has 
  this 
  coarse 
  shingle 
  been 
  derived 
  and 
  how 
  transported. 
  The 
  hard 
  

   masses 
  of 
  silicified 
  wood 
  are 
  of 
  course 
  of 
  local 
  origin, 
  as 
  I 
  shall 
  presently 
  

   show, 
  but 
  whence 
  came 
  the 
  other 
  ingredients 
  ? 
  It 
  is 
  not 
  only 
  along 
  the 
  

   course 
  of 
  the 
  river 
  that 
  these 
  large 
  boulders 
  are 
  seen. 
  They 
  are 
  sparingly, 
  

   and 
  in 
  some 
  spots 
  I 
  may 
  say 
  profusely, 
  scattered 
  over 
  the 
  low 
  outer 
  hills 
  

   in 
  Western 
  Prome, 
  especially 
  along 
  the 
  course 
  of 
  the 
  Maday 
  and 
  Than-ni 
  

   streams, 
  ranging 
  to 
  a 
  height 
  (by 
  a 
  rude 
  guess) 
  of 
  some 
  150 
  or 
  200 
  feet 
  

   above 
  the 
  present 
  stream 
  level. 
  They 
  occur 
  scattered 
  over 
  the 
  hill 
  sides, 
  

   and 
  are 
  clearly 
  beyond 
  the 
  power 
  of 
  the 
  present 
  surface 
  drainage 
  to 
  move 
  

   save 
  by 
  the 
  force 
  of 
  gravity, 
  as 
  the 
  gravel 
  whereon 
  they 
  lie 
  is 
  acted 
  on 
  

   and 
  removed 
  by 
  degrees 
  in 
  the 
  ordinary 
  process 
  of 
  denudation. 
  The 
  

   existence 
  of 
  these 
  boulders 
  and 
  shingle 
  scattered 
  over 
  the 
  lower 
  hills 
  of 
  

   Western 
  Prome, 
  clearly 
  points 
  to 
  their 
  having 
  been 
  there 
  outspread 
  at 
  a 
  

   period 
  anterior 
  to 
  the 
  formation 
  of 
  the 
  present 
  surface 
  features 
  of 
  the 
  

   district 
  ; 
  and 
  the 
  difficulty 
  of 
  supposing 
  their 
  being 
  scattered 
  over 
  the 
  

   hill 
  sides 
  by 
  any 
  fluviatile 
  action, 
  is 
  an 
  additional 
  argument 
  for 
  the 
  

   marine 
  origin 
  of 
  the 
  group 
  to 
  which 
  they 
  belong. 
  I 
  doubt 
  the 
  capacity 
  

   of 
  any 
  of 
  the 
  existing 
  streams, 
  to 
  transport 
  rolled 
  pebbles 
  3, 
  4 
  or 
  6 
  

   inches 
  in 
  diameter 
  ; 
  still 
  more 
  do 
  I 
  doubt 
  the 
  ability 
  of 
  such 
  rivers, 
  to 
  wear 
  

   down 
  into 
  rounded 
  boulders, 
  the 
  hard 
  silicious 
  schists 
  of 
  which 
  this 
  gravel 
  

   is 
  so 
  largely 
  made 
  up. 
  Of 
  course, 
  as 
  the 
  existing 
  streams 
  and 
  rivers 
  

   traverse 
  a 
  country, 
  which, 
  to 
  judge 
  by 
  the 
  remnants 
  still 
  lying 
  on 
  the 
  hill 
  

   sides, 
  was 
  once 
  covered 
  with 
  these 
  well-worn 
  boulders 
  and 
  gravel, 
  their 
  

   beds 
  are 
  full 
  of 
  such 
  materials 
  ; 
  but 
  I 
  greatly 
  distrust 
  the 
  power 
  of 
  any 
  

   such 
  streams 
  to 
  have 
  ever 
  produced 
  or 
  transported 
  such 
  shingle. 
  

  

  The 
  source 
  whence 
  these 
  hard 
  silicious 
  rocks 
  were 
  derived, 
  was 
  for 
  a 
  

   long 
  time 
  a 
  mystery. 
  I 
  felt 
  it 
  probable 
  that 
  they 
  were 
  derived 
  from 
  the 
  

   hardest 
  beds 
  among 
  the 
  altered 
  rocks 
  of 
  the 
  Arakan 
  Yomah, 
  (the 
  Eastern 
  

   Yomah 
  containing 
  no 
  rocks 
  whatever 
  of 
  this 
  character) 
  ; 
  but 
  it 
  was 
  only 
  

  

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