﻿74 
  OLDHAM: 
  GREAT 
  EARTHQUAKE 
  OF 
  1897. 
  

  

  surface 
  of 
  the 
  earth, 
  and 
  of 
  the 
  assumed 
  Increase 
  of 
  velocity 
  of 
  pro- 
  

   pagation 
  with 
  the 
  increase 
  of 
  depth 
  of 
  the 
  wave-path. 
  

  

  Rejecting 
  Schmidt's 
  hypotheses 
  as, 
  in 
  this 
  case, 
  requiring 
  a 
  

   greater 
  variation 
  in 
  the 
  curvature 
  of 
  the 
  hodograph 
  than 
  is 
  indicated 
  

   by 
  the 
  recorded 
  observations, 
  we 
  must 
  fall 
  back 
  on 
  Professor 
  Milne's 
  

   suggestion 
  that 
  the 
  shock 
  which 
  was 
  felt 
  was 
  not 
  the 
  direct 
  result 
  

   of 
  waves 
  propagated 
  from 
  the 
  centre 
  through 
  the 
  earth, 
  but 
  of 
  

   waves 
  of 
  an 
  undulatory 
  nature, 
  originated 
  at 
  the 
  surface 
  in 
  the 
  

   epicentral 
  tract, 
  and 
  propagated 
  outwards 
  along 
  the 
  surface, 
  at 
  a 
  

   uniform 
  rate 
  of 
  travel. 
  

  

  If 
  this 
  is 
  so, 
  the 
  apparent 
  variations 
  in 
  the 
  rate 
  of 
  travel 
  do 
  not 
  

   exist, 
  and 
  the 
  hodograph 
  would 
  be 
  a 
  straight 
  line 
  which 
  may 
  be 
  

   drawn 
  through 
  the 
  Bombay 
  and 
  Calcutta 
  times, 
  continued 
  to 
  50 
  miles 
  

   from 
  the 
  assumed 
  centre, 
  and 
  thence 
  carried 
  horizontally 
  to 
  the 
  

   origin. 
  This, 
  which 
  is 
  shown 
  by 
  the 
  broken 
  line 
  on 
  Plate 
  XXXIX, 
  

   would 
  agree 
  with 
  the 
  recorded 
  observations 
  almost, 
  if 
  not 
  quite, 
  as 
  

   well 
  as 
  the 
  cuved 
  line, 
  and 
  would 
  give 
  a 
  uniform 
  rate 
  of 
  propagation 
  

   of 
  about 
  119 
  miles 
  per 
  minute 
  outside 
  the 
  epicentral 
  tract. 
  

  

  So 
  far 
  as 
  the 
  time 
  observations 
  go, 
  there 
  is 
  nothing 
  to 
  enable 
  us 
  

   to 
  decide 
  between 
  the 
  two, 
  for, 
  though 
  the 
  curved 
  line 
  more 
  closely 
  

   represents 
  the 
  mean 
  of 
  the 
  observations 
  plotted, 
  yet 
  the 
  straight 
  line 
  

   does 
  not 
  anywhere 
  depart 
  from 
  it 
  by 
  more 
  than 
  about 
  half 
  a 
  minute 
  of 
  

   time, 
  while, 
  if 
  we 
  exclude 
  the 
  very 
  discordant 
  records 
  such 
  as 
  those 
  

   from 
  Allahabad 
  and 
  Bareilly, 
  and 
  give 
  less 
  weight 
  to 
  those 
  which 
  

   give 
  times 
  of 
  30 
  or 
  35 
  minutes 
  past 
  4 
  o'clock, 
  and 
  are 
  consequently 
  

   merely 
  approximate 
  in 
  their 
  intention, 
  it 
  will 
  be 
  seen 
  that 
  the 
  

   straight 
  line 
  represents 
  the 
  mean 
  as 
  closely 
  as 
  does 
  the 
  curved 
  line, 
  

   when 
  all 
  the 
  observations 
  are 
  taken 
  into 
  consideration 
  and 
  given 
  

   approximately 
  equal 
  values. 
  When, 
  however, 
  the 
  records 
  of 
  the 
  

   unfelt 
  earthquake 
  at 
  distant 
  observatories 
  come 
  to 
  be 
  considered 
  in 
  

   Chapter 
  XV, 
  we 
  will 
  see 
  that 
  the 
  second 
  explanation, 
  that 
  represent- 
  

   ed 
  by 
  the 
  dotted 
  line 
  in 
  Plate 
  XXXIX, 
  is 
  the 
  more 
  probable 
  one 
  of 
  

   the 
  two, 
  and 
  we 
  may 
  take 
  it 
  that 
  the 
  earthquake 
  wave 
  travelled 
  

  

  ( 
  74 
  ) 
  

  

  