﻿230 
  OLDHAM: 
  GREAT 
  EARTHQUAKE 
  OF 
  1897. 
  

  

  The 
  instrument 
  (5) 
  was 
  observed 
  immediately 
  after 
  the 
  sounding 
  

   of 
  the 
  alarm. 
  The 
  E-W 
  level 
  was 
  specially 
  disturbed 
  and 
  was 
  making 
  

   oscillations 
  of 
  not 
  less 
  than 
  1" 
  of 
  arc 
  during 
  the 
  first 
  phase. 
  

   The 
  movement 
  had 
  almost 
  ceased 
  when, 
  at 
  nh. 
  42m. 
  the 
  oscillations 
  

   became 
  considerable, 
  reaching, 
  at 
  nh. 
  47m., 
  an 
  excursion 
  of 
  4'5" 
  of 
  

   arc 
  from 
  E 
  to 
  W, 
  and 
  3*0" 
  from 
  N 
  to 
  S, 
  with 
  a 
  complete 
  period 
  of 
  

   15s. 
  to 
  20s. 
  After 
  I2h. 
  the 
  oscillations 
  diminished 
  and 
  at 
  12 
  h. 
  20 
  m. 
  

   there 
  was 
  only 
  a 
  movement 
  of 
  about 
  0'$" 
  on 
  each 
  level. 
  

  

  The 
  spring 
  (6) 
  showed, 
  after 
  ufh., 
  vertical 
  oscillations 
  of 
  not 
  

   more 
  than 
  2 
  mm. 
  

  

  Fairly 
  satisfactory 
  diagrams 
  were 
  obtained 
  from 
  (7) 
  and 
  (9), 
  

   considering 
  the 
  slowness 
  of 
  travel 
  of 
  the 
  record. 
  

  

  No. 
  (8) 
  gave 
  by 
  far 
  the 
  clearest 
  and 
  most 
  prolonged 
  diagram, 
  for 
  

   as 
  late 
  as 
  22h. 
  there 
  were 
  still 
  oscillations, 
  showing 
  that 
  the 
  earth 
  only 
  

   came 
  to 
  rest 
  after 
  eleven 
  hours 
  ; 
  it 
  is 
  probable 
  that 
  these 
  were 
  the 
  

   effect 
  of 
  later 
  shocks, 
  registered 
  by 
  this, 
  but 
  not 
  by 
  the 
  other 
  

   instruments. 
  

  

  From 
  the 
  combination 
  of 
  these 
  records, 
  and 
  especially 
  those 
  of 
  

   (2) 
  and 
  (8) 
  we 
  may 
  obtain 
  with 
  certainty 
  the 
  following 
  results 
  :— 
  

  

  Commencement 
  of 
  the 
  rapid 
  vibrations 
  

   Maximum 
  of 
  ditto 
  

  

  Commencement 
  of 
  the 
  slower 
  movement 
  ' 
  

   Commencement 
  of 
  large 
  undulations 
  

   Maximum 
  of 
  the 
  same 
  

   Decrease 
  of 
  the 
  same 
  .... 
  

   End 
  of 
  phase 
  of 
  sensible 
  movement 
  

  

  With 
  reference 
  to 
  the 
  above 
  results 
  Prof. 
  Grablowitz 
  points 
  

   out 
  that 
  there 
  are 
  two 
  principal 
  phases 
  deserving 
  special 
  examina- 
  

   tion, 
  the 
  maximumof 
  rapid 
  motion, 
  at 
  uh. 
  19m., 
  and 
  the 
  maximum 
  of 
  

   slow 
  movement, 
  of 
  a 
  complete 
  period 
  of 
  about 
  20 
  seconds 
  > 
  at 
  1 
  111.47m. 
  

   The 
  amplitude 
  of 
  movement 
  in 
  the 
  two 
  phases 
  varies 
  much 
  in 
  the 
  

   different 
  instruments, 
  but 
  if 
  their 
  different 
  conditions 
  are 
  considered, 
  

  

  1 
  Maximum 
  of 
  this 
  phase 
  uh. 
  27111.403.; 
  Boll. 
  Soc. 
  Sismol. 
  Ital, 
  III, 
  pt. 
  ii, 
  p. 
  26. 
  

   The 
  time 
  of 
  commencement 
  is 
  given 
  as 
  uh. 
  25m. 
  488. 
  

  

  ( 
  23° 
  ) 
  

  

  H. 
  

  

  M. 
  

  

  S. 
  

  

  . 
  11 
  

  

  17 
  

  

  13 
  

  

  . 
  11 
  

  

  19 
  

  

  3 
  

  

  . 
  11 
  

  

  26 
  

  

  

  

  . 
  11 
  

  

  42 
  

  

  33 
  

  

  . 
  11 
  

  

  47 
  

  

  

  

  . 
  11 
  

  

  57 
  

  

  

  

  • 
  13 
  

  

  

  

  

  

  