﻿THE 
  UNFELT 
  EARTHQUAKE. 
  239 
  

  

  14b. 
  6m. 
  1 
  The 
  amplitude 
  of 
  the 
  recorded 
  oscillations 
  of 
  the 
  mirror 
  

   when 
  at 
  its 
  maximum 
  was 
  equivalent 
  to 
  a 
  tilting 
  of 
  the 
  whole 
  instru- 
  

   ment 
  through 
  20" 
  of 
  arc 
  ; 
  but 
  in 
  the 
  gap, 
  where 
  the 
  oscillations 
  were 
  

   too 
  great 
  to 
  be 
  photographically 
  recorded, 
  it 
  must 
  have 
  been 
  greater. 
  

  

  In 
  discussing 
  these 
  observations 
  the 
  first 
  point 
  to 
  be 
  noticed 
  is 
  

   that 
  there 
  are 
  three 
  distinct 
  phases 
  and 
  seven 
  epochs, 
  which 
  can 
  be 
  

   recognised 
  in 
  the 
  records. 
  The 
  phases 
  are 
  (1) 
  the 
  first 
  phase, 
  con- 
  

   sisting 
  of 
  nearly 
  horizontal 
  rapid 
  displacements 
  of 
  the 
  instruments 
  

   unaccompanied 
  by 
  undulating 
  movement 
  of 
  the 
  ground, 
  (2) 
  the 
  

   second 
  phase, 
  during 
  which 
  there 
  were 
  distinct 
  undulations, 
  appar- 
  

   ently 
  accompanied 
  by 
  angular 
  tilting 
  of 
  the 
  instruments, 
  and 
  (3) 
  the 
  

   great 
  oscillations 
  commencing 
  at 
  about 
  11-45. 
  The 
  epochs 
  which 
  

   can 
  be 
  recognised 
  more 
  or 
  less 
  distinctly 
  on 
  the 
  records 
  are— 
  

  

  (1) 
  The 
  first 
  commencement 
  of 
  disturbances. 
  

  

  (2) 
  The 
  maximum 
  of 
  the 
  movement 
  of 
  the 
  first 
  phase. 
  

  

  (3) 
  The 
  commencement 
  of 
  the 
  undulatory 
  movement 
  of 
  the 
  

  

  second 
  phase, 
  

  

  (4) 
  The 
  maximum 
  of 
  the 
  same. 
  

  

  (5) 
  The 
  commencement 
  of 
  the 
  larger 
  undulations. 
  

  

  (6) 
  The 
  maximum 
  of 
  these 
  larger 
  undulations. 
  

  

  (7) 
  The 
  cessation 
  of 
  the 
  disturbance. 
  

  

  One 
  or 
  all 
  of 
  the 
  epochs 
  can 
  be 
  determined 
  on 
  all 
  the 
  traces, 
  

  

  and 
  the 
  respective 
  times 
  are 
  given 
  in 
  the 
  tabular 
  statement 
  on 
  

  

  the 
  following 
  page, 
  the 
  time 
  being 
  minutes 
  and 
  seconds 
  after 
  

   nh. 
  Greenwich 
  mean 
  time: 
  — 
  

  

  1 
  In 
  the 
  published 
  account 
  i3h. 
  12m. 
  I 
  am 
  indebted 
  to 
  Prof. 
  R. 
  Copeland, 
  Astronomer 
  

   Royal, 
  for 
  the 
  information 
  that 
  a 
  reexamination 
  of 
  the 
  record 
  showed 
  that 
  the 
  disturbance 
  

   could 
  be 
  traced 
  for 
  a 
  longer 
  period 
  than 
  was 
  originally 
  supposed. 
  

  

  ( 
  *39 
  ) 
  

  

  