﻿FISSURES 
  AND 
  VENTS. 
  85 
  

  

  seen, 
  we 
  may 
  conclude 
  that 
  the 
  house 
  moved 
  10 
  inches 
  relatively 
  to 
  

   the 
  ground. 
  In 
  either 
  case 
  the 
  relative 
  movement 
  was 
  probably 
  less 
  

   than 
  the 
  actual, 
  for 
  the 
  houses 
  would, 
  to 
  some 
  extent, 
  be 
  dragged 
  

   along 
  by 
  their 
  attachment, 
  and 
  it 
  may 
  be 
  taken 
  that 
  the 
  amplitude 
  of 
  

   the 
  wave 
  at 
  Tura 
  was 
  not 
  less 
  than 
  6 
  inches, 
  or 
  the 
  total 
  backward 
  

   and 
  forward 
  travel 
  of 
  the 
  wave 
  particle 
  12 
  inches. 
  

  

  I 
  was 
  also 
  informed 
  by 
  Mr. 
  Dring 
  that 
  after 
  the 
  great 
  shock 
  was 
  

   over, 
  he 
  went 
  across 
  to 
  a 
  neighbouring 
  house, 
  which 
  had 
  been 
  wrecked, 
  

   and 
  on 
  the 
  road 
  he 
  saw 
  a 
  fissure, 
  the 
  opposite 
  sides 
  of 
  which 
  were 
  

   moving 
  up 
  and 
  down 
  to 
  the 
  extent 
  of 
  a 
  couple 
  of 
  inches. 
  Besides 
  

   these 
  measurements 
  of 
  the 
  range 
  of 
  motion 
  I 
  noticed 
  throughout 
  

   the 
  Khasi 
  hills, 
  that 
  vacant 
  spaces 
  by 
  the 
  side 
  of 
  large 
  boulders 
  

   were 
  common 
  and 
  frequently 
  four 
  or 
  five 
  inches 
  across, 
  even 
  when 
  

   I 
  saw 
  them, 
  about 
  six 
  months 
  after 
  the 
  shock; 
  originally 
  they 
  must 
  

   have 
  been 
  larger, 
  and 
  it 
  may, 
  I 
  think, 
  be 
  taken 
  that 
  throughout 
  

   the 
  whole 
  tract 
  lying 
  west 
  of 
  Shillong 
  and 
  Gauhati, 
  as 
  far 
  as 
  the 
  hills 
  

   extend, 
  and 
  probably 
  over 
  a 
  large 
  area 
  of 
  the 
  plains 
  besides, 
  the 
  

   amplitude 
  of 
  the 
  wave 
  motion 
  was 
  nowhere 
  less 
  than 
  3 
  inches, 
  

   while 
  in 
  many 
  places 
  it 
  was 
  over 
  6 
  inches, 
  the 
  extreme 
  range 
  of 
  

   motion 
  of 
  the 
  wave 
  particle 
  being 
  twice 
  these 
  amounts. 
  

  

  Chapter 
  VJ.-EARTH 
  FISSURES, 
  SAND 
  VENTS, 
  AND 
  ALLIED 
  

  

  PHENOMENA. 
  

  

  Fissures 
  in 
  the 
  ground, 
  and 
  the 
  formation 
  of 
  vents 
  from 
  which 
  

   sand, 
  water 
  and 
  mud 
  have 
  been 
  poured 
  out, 
  are 
  phenomena 
  which 
  have 
  

   been 
  known 
  to 
  accompany 
  almost 
  every 
  really 
  great 
  earthquake, 
  

   and 
  even 
  moderate 
  ones, 
  where 
  favourable 
  conditions 
  have 
  existed, 
  

   but 
  in 
  no 
  case, 
  of 
  which 
  there 
  is 
  historic 
  record, 
  have 
  they 
  been 
  so 
  

   widespread 
  or 
  so 
  numerous 
  as 
  in 
  the 
  great 
  earthquake 
  of 
  1897. 
  

  

  The 
  theory 
  of 
  their 
  formation 
  was 
  first 
  clearly 
  understood 
  in 
  the 
  

   case 
  of 
  the 
  Cachar 
  earthquake 
  of 
  1869, 
  1 
  and 
  the 
  explanation 
  has 
  been 
  

  

  ' 
  R. 
  Mallet 
  and 
  T. 
  Oldham 
  : 
  Notice 
  of 
  Some 
  Secondary 
  Effects 
  of 
  the 
  Earthquake 
  of 
  10th 
  

   January, 
  1S69, 
  in 
  Cachar 
  : 
  Quart. 
  Jour. 
  Geol. 
  Sec, 
  XXVIII, 
  255-270 
  (1872). 
  See 
  also 
  Mem- 
  

   Geol. 
  Surv. 
  Ind., 
  XIX, 
  46-60. 
  (1882). 
  

  

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