﻿GENERAL 
  SKETCH 
  OP 
  AREA. 
  6 
  

  

  Of 
  lagoons 
  and 
  backwaters 
  there 
  are 
  several 
  good 
  examples, 
  as 
  

  

  the 
  Pulicat 
  lake, 
  the 
  Ennore 
  and 
  Covelong 
  back- 
  

  

  -Lagoons. 
  

  

  waters, 
  all 
  of 
  which 
  are 
  salt-water 
  lagoons, 
  but 
  

  

  much 
  influenced 
  by 
  heavy 
  rains, 
  which 
  fall 
  generally 
  during 
  the 
  

  

  north-east 
  monsoon. 
  Unless 
  the 
  flood- 
  water 
  breaches 
  the 
  sandbars 
  

  

  thrown 
  up 
  by 
  the 
  surf 
  across 
  their 
  openings 
  into 
  the 
  sea, 
  the 
  water 
  in 
  

  

  the 
  lagoons 
  loses 
  its 
  salt 
  character, 
  so 
  much 
  as 
  to 
  cause 
  a 
  nearly 
  total 
  

  

  destruction 
  of 
  the 
  estuarine 
  fauna 
  generally 
  found 
  in 
  them."* 
  

  

  No 
  forests 
  occur 
  anywhere 
  within 
  the 
  limits 
  above 
  specified, 
  but 
  

  

  some 
  large 
  patches 
  and 
  many 
  strips 
  of 
  scrub- 
  

   Absence 
  of 
  forests. 
  

  

  jungle 
  occur 
  on 
  and 
  among 
  the 
  Sadras 
  hills, 
  which 
  

  

  furnish 
  a 
  great 
  part 
  of 
  the 
  firewood 
  used 
  in 
  Madras. 
  The 
  Alicoor 
  and 
  

  

  Sattavedu 
  hills 
  are 
  also 
  covered 
  in 
  great 
  measure 
  by 
  low 
  brushwood 
  

  

  jungle. 
  The 
  accompanying 
  long 
  section 
  from 
  Naggery 
  Nose 
  to 
  the 
  sea 
  

  

  near 
  Palaveram, 
  (Plate 
  A,) 
  gives 
  a 
  good 
  idea 
  of 
  the 
  gradual 
  rise 
  of 
  the 
  

  

  ground 
  and 
  of 
  the 
  manner 
  in 
  which 
  the 
  several 
  great 
  alluvial 
  valleys 
  

  

  divide 
  the 
  area 
  occupied 
  by 
  the 
  older 
  rocks 
  into 
  bands 
  and 
  patches 
  by 
  

  

  masking 
  great 
  part 
  of 
  their 
  surfaces. 
  

  

  The 
  various 
  geological 
  formations 
  met 
  with 
  in 
  the 
  area 
  under 
  

  

  consideration, 
  may 
  be 
  conveniently 
  classed, 
  according 
  to 
  their 
  relative 
  

  

  geological 
  ages, 
  in 
  a 
  tabular 
  arrangement 
  as 
  below 
  : 
  — 
  

  

  /■Blown 
  sands. 
  

   1. 
  Recent 
  or 
  quaternary 
  deposits. 
  -< 
  Alluvia, 
  marine 
  and 
  fluviatile. 
  

  

  (Laterite 
  and 
  Conjeveram 
  gravels. 
  

  

  Gritty 
  sandstones- 
  (? 
  Cuddalore 
  sandstones). 
  

   ( 
  (Cretaceous 
  ?). 
  

   | 
  Jurassic, 
  Rajmahal 
  plant 
  beds. 
  

  

  Kadapa 
  group. 
  

   f 
  Gneissic 
  series, 
  (including 
  intrusive 
  

   1 
  trappean 
  rocks). 
  

  

  2. 
  Tertiary? 
  

  

  3. 
  Secondary 
  

  

  4. 
  Sub-rnetamorphic 
  ? 
  

  

  5. 
  Metamorpbic 
  

  

  * 
  This 
  has 
  happened 
  from 
  time 
  to 
  time 
  in 
  the 
  case 
  of 
  the 
  Covelong 
  backwater, 
  

   according 
  to 
  the 
  statements 
  of 
  the 
  natives 
  living 
  on 
  its 
  banks, 
  owiug 
  to 
  the 
  insufficiency 
  

   of 
  the 
  flood 
  waters 
  to 
  breach 
  the 
  bars. 
  This 
  cannot 
  again 
  happen, 
  now 
  that 
  it 
  is 
  connected 
  

   by 
  the 
  coast 
  canal 
  with 
  the 
  estuary 
  of 
  the 
  Adyar, 
  the 
  bar 
  of 
  which 
  is 
  opened 
  every 
  year. 
  

  

  ( 
  o 
  ) 
  

  

  