﻿OLDHAM: 
  GREAT 
  EARTHQUAKE 
  OF 
  1897. 
  

  

  in 
  all 
  the 
  following 
  calculations 
  ; 
  this 
  being 
  more 
  or 
  less 
  of 
  a 
  com* 
  

   promise 
  1 
  . 
  

  

  Taking 
  this 
  as 
  the 
  starting 
  point, 
  we 
  find 
  the 
  distances, 
  mea- 
  

   sured 
  along 
  the 
  surface 
  2 
  , 
  to 
  Bombay 
  and 
  Calcutta 
  are 
  1208*3 
  anc 
  * 
  255*5 
  

   statute 
  miles, 
  respectively, 
  while^the 
  time 
  interval 
  was 
  8 
  minutes. 
  

   From 
  this 
  we 
  find 
  the 
  average 
  rate 
  of 
  travel 
  of 
  the 
  earthquake 
  wave, 
  

   as 
  between 
  these 
  distances, 
  was 
  probably 
  119.1 
  miles 
  per 
  minute, 
  or 
  

   3 
  kilometres 
  per 
  second. 
  The 
  time 
  interval 
  cannot 
  be 
  depended 
  on 
  

   for 
  absolute 
  accuracy; 
  it 
  might 
  possibly 
  be 
  as 
  much 
  as 
  one 
  minute 
  in 
  

   error, 
  but, 
  seeing 
  the 
  nature 
  of 
  the 
  records 
  by 
  which 
  it 
  was 
  obtained^ 
  

   it 
  is 
  probably 
  not 
  more 
  than 
  half 
  a 
  minute 
  out 
  in 
  excess 
  or 
  defect. 
  

   Assuming 
  this 
  as 
  a 
  probable 
  error, 
  we 
  get 
  the 
  values 
  of 
  the 
  rate 
  of 
  

   propagation 
  as 
  — 
  

  

  

  Per 
  Minute. 
  

   Miles. 
  

  

  126*5 
  

   111-7 
  

   119/1 
  

  

  

  Per 
  Second. 
  

  

  

  Maximum 
  

   Minimum 
  

   Probable 
  mean 
  

  

  Miles. 
  

  

  2'IO 
  

  

  1-86 
  

   1*98 
  

  

  Feet. 
  

  

  n,i35 
  

  

  9,725 
  

  

  io,4fo 
  

  

  Kilometres. 
  

  

  3*2 
  

   2-8 
  

   3'o 
  

  

  Making 
  all 
  allowances 
  for 
  possible 
  inaccuracies, 
  there 
  remains 
  

   the 
  fact 
  that 
  the 
  mean 
  rate 
  of 
  travel 
  of 
  the 
  earthquake 
  wave 
  at 
  the 
  

   surface 
  of 
  the 
  earth 
  was 
  about 
  120 
  miles 
  a 
  minute, 
  or 
  3 
  kilometres 
  

   a 
  second, 
  as 
  between 
  Calcutta 
  and 
  Bombay. 
  

  

  The 
  remaining 
  observations 
  are 
  not 
  sufficiently 
  accurate, 
  or 
  

   sufficiently 
  concordant 
  to 
  permit 
  of 
  their 
  being 
  advantageously 
  

   treated 
  by 
  direct 
  calculation, 
  and 
  a 
  more 
  satisfactory 
  result 
  is 
  

   to 
  be 
  obtained 
  by 
  the 
  graphic 
  treatment 
  adopted 
  in 
  the 
  hodo- 
  

   graph 
  on 
  Plate 
  XXXIX. 
  Here 
  the 
  two 
  lines 
  at 
  right 
  angles 
  to 
  

   each 
  other 
  represent, 
  respectively, 
  a 
  scale 
  of 
  distances 
  and 
  time, 
  

  

  1 
  It 
  may 
  be 
  pointed 
  out 
  that, 
  as 
  the 
  stations 
  from 
  which 
  we 
  have 
  time 
  observations 
  are 
  

   in 
  an 
  approximately 
  east 
  and 
  west 
  line, 
  an 
  easteily 
  or 
  westerly 
  shifting 
  of 
  the 
  assumed 
  focus 
  

   would 
  make 
  little 
  or 
  no 
  alteration 
  in 
  the 
  difference 
  of 
  distance 
  of 
  any 
  two 
  stations 
  from 
  it. 
  

   The 
  only 
  exception 
  to 
  this 
  is 
  in 
  the 
  case 
  of 
  stations 
  like 
  Calcutta, 
  which 
  lie 
  far 
  scuth 
  of 
  the 
  

   general 
  E. 
  VV. 
  line; 
  and 
  even 
  here, 
  when 
  compared 
  with 
  distant 
  stations, 
  such 
  as 
  Bombay, 
  

   the 
  difference 
  is 
  not 
  such 
  as 
  to 
  appreciaoly 
  vitiate 
  the 
  results 
  obtained. 
  

  

  2 
  These 
  distances, 
  and 
  all 
  others 
  in 
  this 
  memoir, 
  are 
  calculated 
  to 
  a 
  mean 
  radius 
  of 
  3,956 
  

   miles 
  and 
  a 
  spherical 
  globe. 
  The 
  errors 
  so 
  introduced 
  are 
  trivial 
  in 
  comparison 
  with 
  tfee 
  

   inevitable 
  errors 
  of 
  the 
  time 
  observations. 
  

  

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  7« 
  ) 
  

  

  