﻿FISSURFS 
  AND 
  VENTS 
  93 
  

  

  peiulkular 
  drop, 
  as 
  at 
  bc> 
  fig. 
  n. 
  From 
  b 
  outwards 
  from 
  the 
  hill 
  was 
  

  

  mm/, 
  

  

  Fig. 
  ii. 
  Diagram 
  to 
  illustrate 
  the 
  displacement 
  of 
  alluvium 
  along 
  the 
  foot 
  o( 
  a 
  hill. 
  

  

  a 
  depressed 
  area 
  of 
  from 
  10 
  to 
  20 
  feet 
  broad 
  in 
  which 
  the 
  water 
  had 
  

   accumulated 
  and 
  completely 
  flooded 
  the 
  fields 
  ; 
  immediately 
  outside 
  

   this 
  was 
  a 
  strip, 
  d 
  ) 
  which 
  had 
  evidently 
  been 
  raised 
  above 
  its 
  original 
  

   level, 
  for 
  the 
  water 
  could 
  no 
  longer 
  be 
  led 
  onto 
  it, 
  and 
  beyond 
  this 
  

   came 
  the 
  alluvium, 
  'preserving 
  its 
  original 
  level 
  and 
  apparently 
  

   undisturbed, 
  except 
  where 
  it 
  has 
  been 
  cut 
  by 
  fissures. 
  

  

  These 
  features 
  clearly 
  reveal 
  what 
  has 
  taken 
  place. 
  The 
  thrust 
  

   of 
  the 
  hill 
  and 
  plain 
  against 
  one 
  another 
  has 
  caused 
  the 
  alluvium 
  to 
  

   be 
  thrust 
  forward 
  and 
  raised 
  into 
  the 
  low 
  ridge 
  or 
  roll 
  at 
  d 
  ) 
  while 
  on 
  

   the 
  return 
  a 
  space 
  was 
  left 
  which 
  could 
  not 
  be 
  filled 
  up 
  by 
  the 
  

   alluvial 
  soil 
  without 
  its 
  surface 
  being 
  lowered. 
  As 
  in 
  the 
  case 
  of 
  the 
  

   depression 
  of 
  a 
  wedge 
  of 
  alluvium 
  referred 
  to 
  above, 
  the 
  action 
  was 
  

   doubtless 
  not 
  completed 
  by 
  a 
  single 
  movement, 
  but 
  was 
  the 
  cumula- 
  

   tive 
  result 
  of 
  a 
  succession 
  of 
  waves 
  of 
  compression. 
  

  

  On 
  the 
  borders 
  of 
  the 
  alluvial 
  plain 
  of 
  the 
  Brahmaputra 
  cul- 
  

   tivation 
  does 
  not 
  extend 
  right 
  up 
  to 
  the 
  edge 
  of 
  the 
  hills, 
  and 
  we 
  

   lose 
  the 
  datum 
  level 
  afforded 
  by 
  the 
  ricefields, 
  but 
  the 
  same 
  action 
  

   took 
  place 
  there 
  also, 
  and 
  produced 
  the 
  same 
  result. 
  In 
  no 
  case 
  was 
  

   the 
  subsidence 
  other 
  than 
  local 
  and 
  confined 
  to 
  a 
  very 
  narrow 
  strip 
  

   of 
  land 
  immediately 
  bordering 
  the 
  plane 
  of 
  separation; 
  in 
  some 
  

   places, 
  as 
  on 
  the 
  road 
  from 
  Tura, 
  the 
  amount 
  of 
  subsidence 
  is 
  in- 
  

   creased 
  by 
  the 
  large 
  quantities 
  of 
  sand 
  extravasated, 
  and 
  the 
  impres- 
  

   sion 
  of 
  a 
  general 
  subsidence 
  was 
  favoured 
  by 
  the 
  exceptionally 
  high 
  

  

  ( 
  93 
  ) 
  

  

  