﻿THE 
  LATERITIC 
  FORMATIONS. 
  39 
  

  

  tne 
  larger 
  rivers 
  rising 
  on 
  the 
  metamorphie 
  rocks. 
  This 
  may 
  be 
  seen 
  

   any 
  day 
  on 
  the 
  beach 
  of 
  the 
  Coromandel 
  Coast, 
  where 
  the 
  color 
  of 
  

   the 
  sand 
  is 
  a 
  true 
  index 
  of 
  the 
  quantity 
  of 
  the 
  iron 
  sand 
  contained. 
  

   Very 
  frequently 
  scores 
  and 
  sometimes 
  many 
  hundred 
  square 
  yards 
  of 
  the 
  

   beach 
  may 
  be 
  seen 
  of 
  dark 
  black 
  color, 
  and 
  consisting- 
  mainly 
  of 
  

   magnetic 
  iron 
  sand. 
  This 
  is 
  the 
  case 
  to 
  a 
  very 
  remarkable 
  extent 
  

   near 
  Cape 
  Comorin, 
  and 
  on 
  the 
  south 
  coast 
  of 
  the 
  Tinnivelly 
  District. 
  

   The 
  black 
  iron 
  sand 
  is 
  often 
  replaced 
  by 
  dark 
  crimson 
  garnet 
  sand, 
  

   but 
  they 
  are 
  often 
  also 
  blended 
  together, 
  or 
  arranged 
  in 
  irregular 
  

   bands 
  of 
  patches 
  with 
  the 
  common 
  pale 
  buff 
  or 
  drab 
  quartz 
  sand; 
  

   producing 
  altogether 
  very 
  striking 
  and 
  pleasing 
  effects 
  by 
  the 
  contrasts 
  

   of 
  color. 
  

  

  The 
  Kistna, 
  and 
  such 
  of 
  its 
  tributaries 
  as 
  flow 
  through 
  the 
  great 
  

   Deccan 
  Trap 
  area, 
  also 
  carry 
  down 
  large 
  quantities 
  of 
  magnetic 
  iron 
  sand 
  

   derived 
  from 
  the 
  trappean 
  rocks. 
  It 
  is 
  evident 
  that 
  the 
  same 
  thing, 
  and 
  

   on 
  a 
  much 
  larger 
  scale, 
  must 
  take 
  place 
  over 
  considerable 
  areas 
  under 
  the 
  

   sea, 
  which, 
  if 
  elevated 
  above 
  sea 
  level 
  and 
  exposed 
  to 
  atmospheric 
  in- 
  

   fluences, 
  might, 
  in 
  the 
  course 
  of 
  ages, 
  be 
  oxidized 
  ; 
  and 
  according 
  to 
  the 
  

   poverty 
  or 
  richness 
  of 
  the 
  sands 
  in 
  iron, 
  we 
  might 
  expect 
  they 
  would 
  

   remain 
  either 
  simple 
  sands 
  or 
  become 
  sands 
  with 
  lateritic 
  grains, 
  

   lateritic 
  gravels 
  ( 
  formed 
  by 
  agglomeration 
  of 
  grains 
  together, 
  the 
  

   cement 
  being 
  peroxide 
  of 
  iron), 
  or, 
  when 
  pebbles 
  existed, 
  lateritic 
  con- 
  

   glomerate. 
  There 
  are 
  many 
  reasons 
  for 
  supposing 
  such 
  processes 
  to 
  have 
  

   actually 
  taken 
  place 
  in 
  the 
  formation 
  of 
  the 
  lateritic 
  deposits 
  before 
  des- 
  

   cribed 
  ; 
  and 
  the 
  supposition 
  that 
  the 
  ferruginous 
  materials 
  were 
  origi- 
  

   nally 
  deposited 
  under 
  water 
  in 
  the 
  state 
  of 
  iron 
  sand 
  unequally 
  distri- 
  

   buted 
  over 
  the 
  bed 
  of 
  the 
  sea, 
  greatly 
  simplifies 
  the 
  explanation 
  of 
  the 
  

   phenomena 
  of 
  the 
  passage 
  of 
  sands 
  into 
  the 
  most 
  compact 
  lateritic 
  

   conglomerates, 
  which 
  may 
  be 
  seen 
  in 
  so 
  many 
  places 
  over 
  the 
  area 
  

   described. 
  

  

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  39 
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