﻿8 
  ' 
  EOOTE 
  : 
  GEOLOGY 
  OF 
  MADRAS. 
  

  

  reference 
  to 
  the 
  geology 
  of 
  the 
  Madras 
  district 
  or 
  of 
  any 
  part 
  included 
  

   within 
  the 
  range 
  of 
  this 
  report. 
  

  

  Captain 
  Newbold's 
  writings 
  which 
  come 
  next 
  in 
  point 
  of 
  time 
  

  

  contain 
  but 
  little 
  information 
  about 
  the 
  Madras 
  

  

  district 
  beyond 
  his 
  describing 
  two 
  sections 
  through 
  

  

  the 
  marine 
  alluvium 
  at 
  Madras 
  ; 
  these 
  descriptions 
  will 
  be 
  found 
  quoted 
  

  

  at 
  p. 
  16 
  of 
  this 
  report. 
  

  

  The 
  ' 
  Red 
  Hills'' 
  near 
  Madras 
  were 
  regarded 
  by 
  Captain 
  Newbold 
  

   as 
  of 
  the 
  same 
  geological 
  age 
  as 
  the 
  Pondicherry 
  ' 
  Red 
  Hills/ 
  He 
  

   also 
  considered 
  the 
  sandstones 
  occurring 
  westward 
  of 
  Poonamallee 
  on 
  

   the 
  road 
  to 
  Sripermatoor, 
  and 
  certain 
  other 
  beds 
  occurring 
  at 
  Permal- 
  

   naigpett, 
  as 
  contemporaneous 
  with 
  the 
  beds 
  at 
  Trivicary 
  (Tiruvakkarei) 
  

   near 
  Pondicherry, 
  which 
  latter 
  belong 
  to 
  the 
  probably 
  tertiary 
  Cuddalore 
  

   sandstone 
  series 
  of 
  Mr. 
  H. 
  F. 
  Blanford. 
  But 
  fossils 
  discovered 
  during 
  

   the 
  progress 
  of 
  the 
  survey 
  in 
  shales 
  conformable 
  to 
  the 
  sandstones 
  near 
  

   Poonamallee 
  show 
  these 
  beds 
  to 
  belong 
  to 
  the 
  much 
  older 
  Rajmahal 
  

   series. 
  Captain 
  Newbold 
  was 
  quite 
  correct 
  in 
  supposing 
  that 
  these 
  beds 
  

   extended 
  to 
  the 
  vicinity 
  of 
  Conjeveram. 
  

  

  In 
  1847 
  a 
  memorandum 
  was 
  . 
  given 
  in 
  the 
  Madras 
  Journal 
  by 
  

   Mr. 
  T. 
  G. 
  Taylor, 
  then 
  Government 
  Astronomer 
  

   at 
  Madras, 
  of 
  the 
  results 
  of 
  a 
  boring 
  executed 
  on 
  

   the 
  beach 
  near 
  the 
  Custom 
  House 
  in 
  1845. 
  The 
  value 
  of 
  this 
  section 
  

   is 
  much 
  diminished, 
  because 
  the 
  thickness 
  of 
  the 
  different 
  strata 
  is 
  not 
  

   oiven, 
  but 
  merely 
  the 
  depths 
  reached 
  on 
  successive 
  days 
  by 
  the 
  boring 
  

   instrument. 
  The 
  boring 
  was 
  only 
  continued 
  to 
  a 
  depth 
  of 
  48 
  feet 
  3 
  

   inches, 
  and 
  did 
  not 
  penetrate 
  the 
  alluvium 
  down 
  to 
  the 
  gneiss, 
  and 
  gives, 
  

   therefore, 
  no 
  information 
  as 
  to 
  the 
  total 
  thickness 
  of 
  the 
  alluvium 
  under 
  

   that 
  part 
  of 
  Madras 
  which 
  is 
  a 
  point 
  of 
  importance 
  and 
  interest. 
  

  

  In 
  1 
  854 
  appeared 
  the 
  first 
  Geological 
  Map 
  of 
  India 
  constructed 
  

  

  by 
  Mr. 
  G. 
  B. 
  Greenough, 
  P. 
  R. 
  S. 
  Unfortunately 
  

   (iiocnougb, 
  1854. 
  . 
  . 
  

  

  this 
  map, 
  though 
  in 
  many 
  respects 
  a 
  highly 
  rnerito- 
  

  

  ( 
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  ) 
  

  

  