﻿UPPER 
  CRETACEOUS 
  SERIES. 
  (iGNEOUS.) 
  55 
  

  

  regarded 
  as 
  a 
  dyke 
  — 
  a 
  conclusion 
  which 
  is 
  confirmed 
  by 
  the 
  blocks 
  (to 
  be 
  

   noticed 
  presently) 
  carried 
  up 
  by 
  it 
  not 
  occurring, 
  as 
  observed 
  by 
  Mr. 
  

   Blanf 
  ord, 
  (< 
  out 
  of 
  one 
  general 
  line."" 
  x 
  These 
  blocks 
  are 
  o£ 
  a 
  greyish- 
  

   looking 
  rock, 
  which, 
  owing 
  probably 
  to 
  the 
  pleasant 
  contrast 
  they 
  present 
  

   to 
  the 
  black 
  rocks 
  of 
  the 
  district, 
  have 
  attracted 
  the 
  attention 
  of 
  several 
  

   observers. 
  2 
  The 
  largest 
  of 
  the 
  most 
  readily 
  accessible 
  is 
  30 
  feet 
  in 
  

   length 
  and 
  14 
  in 
  breadth. 
  It 
  is 
  separated 
  by 
  an 
  oblique 
  crack 
  into 
  two 
  

   unequal 
  and 
  lithologically 
  distinct 
  portions, 
  one 
  being 
  much 
  more 
  coarse- 
  

   grained 
  than 
  the 
  other. 
  3 
  The 
  rock 
  is 
  described 
  as 
  granite 
  by 
  all 
  previous 
  

   writers. 
  The 
  specimen 
  taken, 
  close 
  to 
  the 
  contact 
  with 
  the 
  dyke, 
  is 
  

   rather 
  a 
  felsite, 
  with 
  crystals 
  of 
  quartz, 
  felspar, 
  and 
  mica 
  imbedded 
  in 
  

   a 
  micro-crystalline 
  ground-mass. 
  The 
  quartz 
  contains 
  a 
  large 
  number 
  

   of 
  liquid 
  cavities 
  besides 
  plates 
  of 
  mica. 
  The 
  felspar 
  is 
  considerably 
  

   decomposed, 
  appearing 
  as 
  cloudy 
  patches, 
  and 
  merely 
  changing 
  shades 
  in 
  

   polarised 
  light. 
  The 
  microliths 
  (probably 
  felspar) 
  making 
  up 
  the 
  

   ground-mass 
  appear 
  to 
  assume 
  a 
  sort 
  of 
  wavy 
  or 
  radiating 
  arrangement. 
  

   For 
  about 
  two 
  inches 
  of 
  the 
  contact 
  with 
  the 
  crystalline 
  dyke-rock 
  

   described 
  above, 
  the 
  felsite 
  is 
  irregularly 
  altered, 
  small 
  patches 
  of 
  the 
  

   unaffected 
  rock 
  being 
  traceable 
  nearly 
  down 
  to 
  the 
  very 
  contact. 
  In 
  

   the 
  altered 
  portions 
  (which 
  are 
  coloured 
  more 
  or 
  less 
  dark) 
  the 
  quartz 
  

   appears 
  smaller, 
  dirtier, 
  and 
  less 
  numerous, 
  but 
  is 
  still 
  clearly 
  recognis- 
  

   able 
  ; 
  the 
  other 
  minerals, 
  however, 
  and 
  the 
  characteristic 
  matrix 
  have 
  

   entirely 
  disappeared, 
  and 
  in 
  their 
  place 
  we 
  find 
  a 
  crowd 
  of 
  long, 
  slender, 
  

   and 
  altogether 
  singular-looking 
  crystals 
  which, 
  together 
  with 
  trichites 
  

   and 
  a 
  few 
  grains 
  of 
  what 
  look 
  like 
  magnetite, 
  are 
  interspersed 
  in 
  a 
  matrix 
  

   of 
  crypto-crystalline 
  texture. 
  These 
  crystals 
  are 
  quadrangular 
  in 
  trans- 
  

   verse 
  section. 
  Some 
  show 
  a 
  clear 
  peripheral 
  and 
  a 
  granular 
  dusky 
  central 
  

   portion 
  ; 
  irregular 
  stone 
  enclosures 
  abound 
  in 
  the 
  former, 
  and 
  the 
  cloudy 
  

   central 
  portion 
  appears 
  in 
  several 
  cases 
  to 
  protrude 
  from 
  the 
  matrix. 
  

   Others 
  are 
  dirty 
  throughout 
  with 
  minute 
  granules. 
  Others, 
  again, 
  

   enclose 
  parallel 
  rows 
  of 
  squarish 
  black 
  grains. 
  In 
  polarised 
  light, 
  bright 
  

  

  "Memoirs," 
  Vol. 
  VI, 
  pt. 
  3, 
  p. 
  129. 
  

  

  2 
  See 
  Transactions, 
  Bombay 
  Geog. 
  Soc, 
  Vol. 
  VI, 
  p. 
  7; 
  Journ. 
  A. 
  S. 
  B., 
  Vol. 
  XIV, 
  p. 
  821. 
  

   The 
  crack 
  may 
  be 
  a 
  small 
  fault. 
  

  

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  55 
  ) 
  

  

  