﻿60 
  BOSE 
  : 
  GEOLOGY 
  OF 
  THE 
  LOWER 
  XARBA.DA 
  VALLEY. 
  

  

  up 
  with 
  that 
  sediment. 
  But 
  I 
  had 
  soon 
  to 
  change 
  my 
  mind. 
  The 
  rock 
  

   is 
  unlike 
  any 
  known 
  inter-trappean, 
  and 
  has 
  nowhere 
  yielded 
  a 
  trace 
  of 
  a 
  

   fossil. 
  Had 
  it 
  originated 
  in 
  inter-trappean 
  lakes 
  or 
  lagoon 
  s, 
  the 
  outcrops 
  

   could 
  not 
  have 
  been 
  so 
  uniformly 
  linear 
  and 
  straight 
  and 
  of 
  such 
  frag- 
  

   mentary 
  character. 
  

  

  From 
  a 
  consideration 
  of 
  the 
  vicinity 
  of 
  pre-trappean 
  beds 
  (the 
  Nimar 
  

   sandstone 
  with 
  the 
  overlying 
  upper 
  cretaceous 
  limestones), 
  and 
  the 
  

   occasional 
  association 
  of 
  altered 
  shales 
  and 
  sandstones, 
  there 
  can 
  be 
  very 
  

   little 
  doubt 
  that, 
  in 
  common 
  with 
  these, 
  the 
  rocks 
  under 
  notice 
  have 
  

   been 
  severed 
  and 
  forced 
  up 
  from 
  the 
  infra-trappean 
  beds 
  by 
  intrusive 
  

   rocks. 
  They 
  have 
  been 
  most 
  effectually 
  baked, 
  being 
  rendered 
  quite 
  

   crystalline, 
  the 
  colour 
  changed 
  with 
  remarkable 
  uniformity 
  into 
  yellowish 
  

   or 
  reddish 
  brown 
  ; 
  and, 
  what 
  is 
  most 
  remarkable 
  of 
  all, 
  portions 
  of 
  them 
  

   would 
  appear 
  to 
  have 
  been 
  converted 
  into 
  a 
  trappean 
  substance. 
  A 
  

   somewhat 
  analogous 
  transformation 
  has 
  been 
  noted 
  in 
  connection 
  with 
  

   the 
  Mandlesar 
  dyke. 
  But 
  in 
  the 
  present 
  instance 
  the 
  change 
  is 
  on 
  a 
  

   much 
  larger 
  scale. 
  

  

  To 
  the 
  explanation 
  just 
  offered 
  of 
  the 
  origin 
  of 
  the 
  strange 
  calcareous 
  

   rock, 
  there 
  is 
  one 
  serious 
  objection. 
  We 
  have 
  seen 
  in 
  several 
  cases 
  that 
  

   the 
  heat 
  from 
  dykes 
  has 
  affected 
  the 
  strata 
  in 
  contact 
  only 
  to 
  a 
  small 
  

   extent. 
  In 
  the 
  case 
  at 
  hand, 
  however, 
  several 
  feet 
  of 
  the 
  rock 
  have 
  

   been 
  supposed 
  to 
  be 
  fused, 
  and 
  to 
  such 
  a 
  degree 
  as 
  to 
  be 
  partially 
  con- 
  

   verted 
  into 
  patches 
  of 
  a 
  lava-like 
  substance. 
  The 
  greater 
  intensity 
  of 
  the 
  

   igneous 
  force 
  in 
  this 
  case, 
  as 
  is 
  indicated 
  by 
  the 
  up-lifting 
  of 
  rock-masses 
  

   through 
  several 
  score 
  feet, 
  perhaps 
  explains 
  the 
  difference 
  in 
  part. 
  But 
  

   the 
  fact 
  that 
  these 
  masses, 
  however 
  huge, 
  exert 
  considerably 
  less 
  pressure 
  

   when 
  torn 
  off 
  from 
  their 
  parent 
  beds 
  than 
  when 
  in 
  situ, 
  and 
  thus 
  

   become 
  more 
  liable 
  to 
  fusion, 
  probably 
  accounts 
  for 
  a 
  great 
  deal 
  more. 
  

  

  Several 
  cases 
  of 
  columnar 
  structure 
  have 
  been 
  already 
  noticed 
  ; 
  an 
  

   approach 
  to 
  it 
  is 
  observable 
  everywhere 
  throughout 
  the 
  area. 
  Perfect 
  

   basaltic 
  colonnades 
  were 
  met 
  with 
  by 
  the 
  Uri 
  at 
  Mangdi, 
  about 
  a 
  mile 
  and 
  

   a 
  half 
  south-east 
  of 
  Tanda; 
  by 
  a 
  streamlet 
  which, 
  originating 
  from 
  close 
  

   to 
  the 
  Tanda-Dehri 
  road, 
  joins 
  another 
  at 
  Jamla 
  (three 
  miles 
  and 
  a 
  half 
  

   north-west 
  of 
  Bag) 
  ; 
  at 
  Aolia 
  (7 
  miles 
  south-west 
  of 
  Bag), 
  &c. 
  

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  ) 
  

  

  