﻿OLDER 
  ALLUVIUM. 
  57 
  

  

  it 
  is 
  subjected 
  to 
  atmospheric 
  action, 
  not 
  that 
  all 
  parts 
  of 
  this 
  deposit 
  

   are 
  subject 
  to 
  this 
  conversion, 
  but 
  such 
  only 
  whose 
  composition 
  is 
  favor- 
  

   able 
  to 
  the 
  change. 
  The 
  term 
  ' 
  laterosis' 
  might, 
  in 
  fact, 
  be 
  conveniently 
  

   adopted, 
  to 
  imply 
  the 
  process 
  which 
  in 
  India 
  has 
  from 
  its 
  effects 
  on 
  such 
  

   various 
  rocks, 
  caused 
  such 
  a 
  variety 
  of 
  opinions 
  and 
  speculations 
  regard- 
  

   ing 
  the 
  origin 
  of 
  laterite 
  ; 
  and 
  I 
  would 
  use 
  the 
  term 
  as 
  simply 
  imply- 
  

   ing 
  the 
  conversion 
  of 
  any 
  suitable 
  rock 
  into 
  laterite 
  by 
  the 
  addition 
  

   to 
  it 
  of 
  iron, 
  or 
  the 
  formation 
  or 
  development 
  in 
  it, 
  through 
  atmos- 
  

   pheric 
  action, 
  of 
  the 
  hydrated 
  peroxide 
  of 
  the 
  metal, 
  so 
  familiarly 
  

   seen 
  in 
  the 
  glaze, 
  which 
  covers 
  all 
  lateritic 
  rocks, 
  whether 
  the 
  iron 
  be 
  

   extraneously 
  introduced 
  or 
  originally 
  contained 
  in 
  the 
  rock. 
  In 
  the 
  typi- 
  

   cal 
  laterites 
  of 
  India, 
  this 
  iron 
  cement 
  is 
  a 
  prominent 
  ingredient, 
  often 
  

   sufficient 
  to 
  permit 
  of 
  the 
  rock 
  being 
  smelted 
  as 
  a 
  source 
  of 
  the 
  metal, 
  

   and 
  on 
  its 
  presence 
  largely 
  depends 
  the 
  value 
  of 
  the 
  rock 
  for 
  a 
  building 
  

   or 
  road 
  material 
  ; 
  but 
  in 
  Pegu 
  the 
  type 
  of 
  laterite 
  is 
  much 
  poorer 
  in 
  this 
  

   respect, 
  and 
  good 
  laterite 
  in 
  an 
  economic 
  sense 
  is 
  much 
  scarcer. 
  In 
  

   many 
  places, 
  however, 
  along 
  the 
  Western 
  slopes 
  of 
  the 
  Pegu 
  Yomah 
  

   laterite 
  is 
  found 
  of 
  fair 
  quality 
  underlying 
  the 
  sandy 
  soil 
  of 
  the 
  Engdine 
  

   Forest, 
  where 
  its 
  position 
  is 
  that 
  of 
  a 
  basal 
  member 
  of 
  the 
  older 
  allu- 
  

   vium. 
  On 
  the 
  Eastern 
  side 
  of 
  the 
  Pegu 
  Yomah 
  laterite 
  is 
  generally 
  

   wanting, 
  and 
  its 
  occurrence 
  is 
  exceptional, 
  save 
  close 
  to 
  the 
  frontier, 
  

   where 
  a 
  good 
  deal 
  of 
  laterite 
  occurs, 
  but 
  which, 
  as 
  I 
  shall 
  presently 
  

   show, 
  belongs 
  to 
  another 
  geological 
  group 
  than 
  that 
  of 
  the 
  alluvium 
  I 
  

   am 
  at 
  present 
  concerned 
  with. 
  

  

  Passing, 
  however, 
  beyond 
  the 
  strict 
  limits 
  of 
  Pegu 
  and 
  crossing 
  the 
  

   Sittoung 
  River, 
  good 
  typical 
  laterite, 
  undistinguishable 
  from 
  the 
  Midna- 
  

   pore 
  rock, 
  is 
  found 
  in 
  great 
  force, 
  forming 
  a 
  continuous 
  belt 
  of 
  high 
  

   ground 
  almost 
  scarped 
  as 
  regards 
  the 
  abruptness 
  of 
  its 
  margin 
  towards 
  

   the 
  Sittoung, 
  and 
  forming 
  a 
  plateau 
  of 
  variable 
  breadth 
  thence 
  to 
  the 
  

   foot 
  of 
  the 
  hills, 
  and 
  which 
  covers 
  ground 
  not 
  as 
  yet 
  explored. 
  This 
  

   is 
  the 
  lateritic 
  belt 
  which 
  I 
  have 
  already 
  described 
  as 
  shown 
  in 
  

   h 
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  24,5 
  ) 
  

  

  