﻿130 
  EOOTE 
  : 
  GEOLOGY 
  OE 
  MADRAS. 
  

  

  Palamanair 
  plateau 
  and 
  in 
  its 
  off-shoots, 
  that 
  the 
  great 
  quantities 
  of 
  

   clay 
  occurring" 
  among 
  the 
  Rajmahal 
  formations 
  of 
  the 
  Madras 
  district 
  

   appear 
  to 
  have 
  been 
  derived. 
  

  

  Granitic 
  rocks. 
  

  

  Of 
  these 
  very 
  few 
  examples 
  were 
  met 
  with, 
  none 
  of 
  any 
  importance 
  

   or 
  magnitude, 
  unless 
  the 
  doubtful 
  quartzose 
  ridge 
  of 
  the 
  Apoor 
  hill 
  before 
  

   mentioned 
  be 
  regarded 
  as 
  a 
  vein 
  rock 
  and 
  not 
  as 
  a 
  highly 
  altered 
  bed 
  of 
  

   quartzite. 
  

  

  The 
  only 
  large 
  vein 
  of 
  unquestionable 
  granite 
  was 
  observed 
  at 
  Turroor, 
  

   about 
  eight 
  miles 
  east 
  of 
  the 
  Covrepauk 
  tank, 
  where 
  it 
  forms 
  a 
  bare 
  and 
  

   o-enerally 
  smooth 
  ridge, 
  a 
  mile 
  and 
  quarter 
  long 
  and 
  about 
  40 
  feet 
  in 
  

   height 
  at 
  the 
  highest 
  point. 
  It 
  consists 
  of 
  quartzo-felspathic 
  granite, 
  and 
  

   is 
  apparently 
  a 
  binary 
  rock, 
  for 
  no 
  traces 
  of 
  mica 
  or 
  hornblende 
  could 
  be 
  

   detected. 
  The 
  rock 
  is 
  coarse 
  in 
  grain 
  and 
  full 
  of 
  minute 
  cracks 
  and 
  of 
  

   no 
  value 
  as 
  a 
  building 
  stone. 
  

  

  Whether 
  the 
  handsome 
  red 
  and 
  green 
  syenite 
  rocks 
  occurring 
  in 
  

   the 
  lower 
  parts 
  of 
  the 
  Naggery 
  Nose 
  mountain 
  occur 
  as 
  veins, 
  or 
  are 
  

   only 
  highly 
  altered 
  portions 
  of 
  the 
  gneissic 
  series, 
  is 
  a 
  point 
  that 
  has 
  

   yet 
  to 
  be 
  decided, 
  but 
  they 
  are 
  undoubtedly 
  one 
  source 
  whence 
  came 
  

   the 
  numerous 
  red 
  and 
  green 
  syenite 
  boulders 
  occurring 
  in 
  the 
  boulder 
  

   beds 
  of 
  the 
  Rajmahal 
  system 
  in 
  the 
  Alicoor 
  hills 
  and 
  elsewhere. 
  

  

  Trappean 
  rocks. 
  

   These, 
  though 
  not 
  of 
  rare 
  occurrence 
  within 
  the 
  metamorphic 
  region 
  

   described 
  in 
  this 
  report, 
  are 
  of 
  no 
  great 
  importance, 
  nor 
  of 
  any 
  special 
  

   interest. 
  They 
  belong 
  chiefly 
  to 
  one 
  system, 
  and 
  run 
  generally 
  from 
  

   west 
  by 
  south 
  to 
  east 
  by 
  north, 
  varying 
  a 
  few 
  points 
  north 
  and 
  south, 
  

   in 
  some 
  cases, 
  and 
  occasionally 
  changing 
  the 
  direction 
  of 
  their 
  course. 
  

  

  All 
  the 
  dykes 
  observed 
  within 
  the 
  Chingleput 
  gneiss 
  area 
  consist 
  

   of 
  black 
  hornblendic 
  trap, 
  generally 
  rather 
  coarse 
  in 
  grain, 
  but 
  very 
  

   compact 
  and 
  tough. 
  

  

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