﻿106 
  OLDHMAM 
  : 
  GREAT 
  EARTHQUAKE 
  OF 
  1897. 
  

  

  help 
  to 
  carry 
  off 
  the 
  surplus 
  waters 
  that 
  would 
  otherwise 
  submerge 
  

   the 
  country 
  they 
  drain. 
  Before 
  the 
  earthquake 
  these 
  channels 
  were 
  

   from 
  15 
  to 
  20 
  feet 
  deep, 
  and 
  in 
  the 
  dry 
  weather 
  the 
  country 
  was 
  inter- 
  

   sected 
  by 
  steep-sided 
  depressions 
  of 
  this 
  depth; 
  at 
  the 
  bottom 
  of 
  which 
  

   flowed 
  a 
  shallow 
  stream. 
  During 
  the 
  earthquake 
  the 
  bottoms 
  of 
  all 
  

   these 
  channels 
  were 
  forced 
  up 
  till 
  level 
  with 
  the 
  banks 
  on 
  either 
  

   side, 
  and 
  during 
  the 
  ensuing 
  dry 
  weather 
  the 
  drainage 
  of 
  this 
  tract, 
  

   instead 
  of 
  flowing 
  in 
  deeply 
  sunken 
  channels 
  flowed 
  nearly 
  level 
  with 
  

   the 
  general 
  surface 
  of 
  the 
  land 
  in 
  shallow 
  sandy 
  channels. 
  

  

  This 
  blocking 
  of 
  the 
  drainage 
  channels 
  prevented 
  them 
  from 
  

   serving 
  their 
  natural 
  purpose 
  when 
  the 
  rivers 
  rose 
  in 
  flood, 
  and 
  large 
  

   volumes 
  of 
  water 
  which 
  would 
  otherwise 
  have 
  escaped 
  were 
  forced 
  to 
  

   spread 
  over 
  the 
  surface 
  of 
  the 
  land, 
  thus 
  giving 
  rise 
  to 
  the 
  exceptional 
  

   floods 
  of 
  1897. 
  This 
  matter, 
  being 
  dealt 
  with 
  elsewhere 
  1 
  , 
  will 
  

   not 
  be 
  further 
  referred 
  to, 
  but 
  a 
  direct 
  result 
  of 
  the 
  upheaval 
  of 
  

   the 
  river 
  channels 
  may 
  be 
  noticed. 
  As, 
  this 
  upheaval 
  was 
  not 
  due 
  to 
  

   an 
  eruption 
  of 
  material 
  from 
  a 
  great 
  depth, 
  but 
  to 
  a 
  redistribution 
  

   of 
  comparatively 
  superficial 
  material, 
  the 
  rise 
  of 
  the 
  river 
  beds 
  had 
  to 
  

   be 
  compensated 
  by 
  a 
  corresponding 
  subsidence 
  elsewhere, 
  in 
  general 
  

   immediately 
  contiguous 
  to 
  the 
  river 
  banks. 
  It 
  is 
  obvious, 
  that 
  in 
  a 
  

   material 
  which 
  offers 
  so 
  great 
  internal 
  frictional 
  resistance 
  to 
  deforma- 
  

   tion 
  as 
  the 
  alluvium, 
  the 
  movement 
  by 
  which 
  the 
  deformation 
  took 
  

   place 
  would 
  ordinarily 
  be 
  transmitted 
  to 
  the 
  shortest 
  distance 
  com- 
  

   patible 
  with 
  the 
  effect 
  to 
  be 
  produced; 
  hence 
  for 
  this 
  reason 
  alone 
  

   the 
  subsidence 
  of 
  the 
  banks 
  would 
  probably 
  be 
  greater 
  than 
  that 
  of 
  

   the 
  alluvium 
  further 
  back. 
  

  

  Added 
  to 
  this 
  there 
  are 
  two 
  facts 
  to 
  be 
  considered 
  : 
  firstly 
  that, 
  

   as 
  the 
  alluvium 
  near 
  the 
  river 
  banks 
  was 
  most 
  broken 
  up 
  by 
  fissures, 
  

   the 
  separate 
  blocks 
  would 
  subside 
  more 
  readily 
  than 
  a 
  large 
  continu- 
  

   ous 
  sheet, 
  and 
  secondly 
  that, 
  as 
  is 
  the 
  case 
  with 
  all 
  deltaic 
  rivers, 
  the 
  

   river 
  banks 
  were 
  higher 
  than 
  the 
  land 
  behind 
  them, 
  and 
  the 
  pressure 
  

   on 
  the 
  subjacent 
  yielding 
  layers 
  greater 
  than 
  elsewhere. 
  

  

  1 
  Chap, 
  IX. 
  

  

  ( 
  106 
  ) 
  

  

  