﻿24 
  FOOTE 
  : 
  GEOLOGY 
  OF 
  MADRA.S. 
  

  

  lateritic 
  formations. 
  Eastward 
  of 
  the 
  Nellore 
  high 
  road 
  where 
  the 
  

   lateritic 
  grits 
  become 
  hut 
  very 
  slightly 
  ferruginous, 
  and 
  the 
  alluvial 
  

   sands 
  so 
  abound 
  in 
  lateritic 
  pellets 
  as 
  often 
  to 
  assume 
  a 
  reddish 
  color, 
  

   the 
  distinction 
  between 
  the 
  two 
  formations 
  becomes 
  anything 
  but 
  easy, 
  

   and 
  in 
  the 
  absence 
  of 
  sections 
  is 
  often 
  quite 
  a 
  matter 
  of 
  guess-work. 
  

  

  The 
  mineral 
  character 
  of 
  the 
  Poonamallee-Madras 
  alluvial 
  bay 
  

  

  „ 
  „ 
  ... 
  , 
  is 
  very 
  simple. 
  Near 
  the 
  sea 
  and 
  inland 
  in 
  a 
  west- 
  

  

  Poonamallee-Madras 
  J 
  L 
  

  

  alluvial 
  bay. 
  er 
  ]j 
  direction, 
  so 
  far 
  as 
  Poonamallee, 
  it 
  consists 
  ge- 
  

  

  nerally 
  of 
  pure 
  fine 
  light 
  drab 
  sand. 
  Westward 
  of 
  Poonamallee, 
  the 
  fine 
  

   sand, 
  mixed, 
  near 
  the 
  banks 
  of 
  the 
  Cuum, 
  with 
  a 
  considerable 
  propor- 
  

   tion 
  of 
  clay, 
  passes 
  near 
  Trimalchy 
  and 
  Chittagauda 
  into 
  the 
  coarse 
  

   gritty 
  dusty 
  sand 
  of 
  the 
  old 
  Palar 
  alluvium, 
  which 
  here 
  contains 
  

   (locally) 
  a 
  considerable 
  proportion 
  of 
  washed-up 
  laterite 
  pellets. 
  

  

  The 
  junction 
  of 
  the 
  two 
  alluvia 
  through 
  the 
  valley 
  south 
  of 
  

   Permalpett 
  has 
  been 
  already 
  pointed 
  out. 
  

  

  The 
  junction 
  line 
  of 
  the 
  coarse 
  fluvial 
  sands 
  and 
  the 
  fine 
  marine 
  

  

  sand, 
  trends 
  north-eastward 
  as 
  far 
  as 
  the 
  great 
  tank 
  at 
  Ayapakkam 
  

  

  (Ayappalicum 
  of 
  the 
  map), 
  which 
  village 
  stands 
  on 
  a 
  bank 
  of 
  the 
  

  

  coarse 
  sand 
  raised 
  10 
  or 
  12 
  feet 
  above 
  the 
  general 
  level 
  of 
  the 
  alluvial 
  

  

  « 
  

   plain, 
  and 
  abutting 
  against 
  the 
  slope 
  of 
  the 
  lateritic 
  formations. 
  

  

  Between 
  the 
  villages 
  of 
  Nuttum 
  and 
  Anakaputur 
  (Anacotove 
  of 
  

   map) 
  to 
  the 
  south 
  of 
  Poonamallee 
  is 
  a 
  considerable 
  spread 
  of 
  black 
  soil 
  

   un 
  distinguishable 
  from 
  cotton 
  soil, 
  but 
  which 
  was 
  formed 
  no 
  doubt 
  at 
  

   the 
  bottom 
  of 
  the 
  great 
  Pammal 
  tank, 
  which 
  formerly 
  occupied 
  several 
  

   square 
  miles 
  of 
  country 
  in 
  the 
  valley 
  of 
  the 
  Adyar. 
  

  

  The 
  only 
  organic 
  remains 
  anywhere 
  observed 
  in 
  the 
  alluvial 
  deposits 
  

   Organic 
  remains 
  in 
  proved 
  to 
  belong 
  to 
  existing 
  animals, 
  and 
  were 
  

   very 
  sparingly 
  met 
  with. 
  They 
  consisted 
  of 
  the 
  

   shells 
  of 
  Helices 
  and 
  of 
  other 
  fresh-water 
  mollusca. 
  

   ( 
  M 
  ) 
  

  

  