﻿132 
  OLDHAM: 
  GREAT 
  EARTHQUAKE 
  OF 
  1897. 
  

  

  projected 
  by 
  earthquakes 
  is 
  a 
  commonly 
  observed 
  phenomenon, 
  and 
  

   may 
  in 
  part 
  be 
  attributed 
  to 
  the 
  nature 
  of 
  the 
  impulse 
  imparted 
  by 
  

   the 
  earthquake 
  wave. 
  In 
  the 
  case 
  of 
  these 
  projected 
  stones, 
  how- 
  

   ever, 
  the 
  explanation 
  is 
  probably 
  more 
  simple. 
  In 
  every 
  case 
  

   where 
  a 
  stone, 
  partially 
  imbedded 
  in 
  the 
  earth, 
  was 
  shot 
  out 
  in 
  a 
  

   slanting 
  direction, 
  it 
  had 
  to 
  break 
  down 
  one 
  edge 
  of 
  the 
  cup 
  in 
  which 
  

   it 
  lay, 
  and 
  even 
  where, 
  owing 
  to 
  the 
  form 
  of 
  its 
  under 
  surface 
  no 
  

   actual 
  breaking 
  away 
  of 
  the 
  earth 
  was 
  necessary, 
  there 
  was 
  a 
  

   greater 
  frictional 
  resistance 
  than 
  on 
  the 
  opposite 
  side. 
  Consequently 
  

   that 
  side 
  of 
  the 
  stone, 
  which 
  lay 
  towards 
  the 
  direction 
  in 
  which 
  it 
  was 
  

   thrown, 
  had 
  a 
  slight 
  drag 
  put 
  on 
  it, 
  and 
  so 
  a 
  spin 
  was 
  imparted 
  to 
  the 
  

   stone, 
  which 
  made 
  it 
  turn 
  over 
  in 
  its 
  course. 
  

  

  Another 
  point 
  to 
  be 
  noticed 
  is 
  that 
  the 
  stones 
  which 
  were 
  

   projected 
  were 
  all 
  much 
  of 
  a 
  size 
  and, 
  with 
  very 
  few 
  exceptions, 
  from 
  

   about 
  1 
  ft. 
  to 
  3 
  ft. 
  in 
  diameter. 
  The 
  reason 
  of 
  this 
  is 
  not 
  far 
  to 
  seek 
  ; 
  

   each 
  stone, 
  partially 
  imbedded 
  in 
  the 
  ground, 
  was 
  restrained 
  by 
  the 
  

   adhesion 
  of 
  the 
  soil 
  to 
  the 
  stone, 
  a 
  restraint 
  which 
  had 
  to 
  be 
  overcome 
  

   by 
  the 
  momentum 
  imparted 
  to 
  the 
  stone 
  by 
  the 
  earthquake 
  wave. 
  

  

  The 
  adhesion 
  is 
  proportional 
  to 
  the 
  surface 
  in 
  contact 
  with 
  

   the 
  earth, 
  and 
  increases 
  with 
  the 
  square 
  of 
  the 
  dimensions 
  of 
  the 
  

   stone 
  ; 
  the 
  force 
  which 
  tends 
  to 
  overcome 
  this 
  adhesion 
  varies 
  with 
  

   the 
  mass 
  of 
  the 
  stone, 
  that 
  is 
  to 
  say, 
  with 
  the 
  cube 
  of 
  the 
  dimensions. 
  

   In 
  the 
  case 
  of 
  very 
  small 
  stones, 
  then, 
  the 
  momentum 
  imparted 
  to 
  the 
  

   stone 
  is 
  not 
  sufficient 
  to 
  overcome 
  the 
  attachment, 
  but 
  as 
  the 
  

   dimensions 
  increase 
  a 
  limit 
  is 
  reached, 
  when 
  the 
  pull 
  of 
  the 
  stone 
  is 
  

   sufficient 
  to 
  allow 
  it 
  to 
  become 
  detached 
  from 
  the 
  soil. 
  The 
  exact 
  

   size 
  of 
  stone 
  at 
  which 
  this 
  becomes 
  possible 
  depends 
  on 
  several 
  

   factors, 
  the 
  maximum 
  velocity 
  imparted 
  to 
  the 
  stone, 
  its 
  specific 
  

   gravity, 
  the 
  nature 
  and 
  degree 
  of 
  moisture 
  of 
  the 
  soil, 
  and 
  the 
  form 
  of 
  

   the 
  cavity 
  left 
  by 
  the 
  stone. 
  With 
  the 
  conditions 
  prevailing 
  in 
  the 
  

   Khasi 
  Hills, 
  at 
  the 
  time 
  of 
  this 
  earthquake, 
  the 
  limit 
  was, 
  as 
  has 
  been 
  

   stated, 
  about 
  1 
  ft. 
  in 
  diameter. 
  Smaller 
  pieces 
  were 
  occasionally 
  

   projected, 
  but 
  this 
  was 
  comparatively 
  rare, 
  except 
  in 
  the 
  case 
  of 
  

   pieces 
  lying 
  absolutely 
  loose 
  on 
  the 
  surface. 
  

   ( 
  132 
  ) 
  

  

  