﻿238 
  OLDHAM 
  : 
  GREAT 
  EARTHQUAKE 
  OF 
  1897. 
  

  

  52m. 
  15s. 
  in 
  advance 
  of 
  Greenwich. 
  The 
  G. 
  M. 
  T. 
  of 
  commencement 
  

   is, 
  therefore, 
  1 
  ih. 
  18m. 
  45s. 
  The 
  times 
  can 
  be 
  relied 
  on 
  to 
  half 
  

   a 
  minute. 
  At 
  nh. 
  37m. 
  G. 
  M. 
  T. 
  the 
  horizontal 
  pendulum 
  was 
  

   thrown 
  out 
  of 
  gear 
  and 
  the 
  record 
  ceased. 
  

  

  Newport, 
  I. 
  W. 
  — 
  At 
  Shide, 
  hear 
  Newport, 
  in 
  the 
  Isle 
  of 
  Wight, 
  

   Prof. 
  J. 
  Milne, 
  F.R.S., 
  has 
  established 
  a 
  seismograph 
  of 
  his 
  own 
  

   design. 
  The 
  record 
  is 
  photographic, 
  and 
  unfortunately 
  a 
  change 
  of 
  

   paper 
  was 
  being 
  made 
  when 
  the 
  disturbance 
  commenced 
  ; 
  the 
  record 
  

   of 
  the 
  commencement 
  of 
  this 
  earthquake 
  was 
  consequently 
  lost, 
  

   but 
  the 
  end 
  of 
  the 
  disturbance 
  was 
  determined 
  as 
  14I1. 
  32m. 
  51s. 
  

   The 
  largest 
  angular 
  tilt 
  recorded 
  was 
  5" 
  of 
  arc, 
  but 
  it 
  may 
  have 
  

   been 
  greater 
  in 
  the 
  part 
  of 
  the 
  record 
  which 
  was 
  lost. 
  A 
  horizontal 
  

   pendulum 
  with 
  a 
  boom 
  4 
  ft. 
  long 
  gave 
  the 
  period 
  of 
  the 
  large 
  oscil- 
  

   lation 
  as 
  15s. 
  

  

  Edinburgh. 
  — 
  At 
  the 
  Royal 
  Observatory, 
  Edinburgh, 
  is 
  a 
  bifilar 
  

   pendulum, 
  an 
  instrument 
  consisting, 
  of 
  a 
  mirror 
  hung 
  from 
  two 
  

   threads 
  of 
  unequal 
  length 
  whose 
  upper 
  ends 
  are 
  fastened 
  nearly 
  

   vertically 
  above 
  each 
  other. 
  As 
  long 
  as 
  the 
  two 
  points 
  of 
  suspension 
  

   and 
  the 
  two 
  points 
  of 
  attachment 
  remain 
  in 
  the 
  same 
  vertical 
  

   plane, 
  the 
  mirror 
  remains 
  at 
  rest, 
  but 
  as 
  soon 
  as 
  it 
  is 
  tilted 
  in 
  the 
  

   slightest 
  degree 
  in 
  any 
  direction, 
  except 
  that 
  of 
  this 
  plane, 
  the 
  mirror 
  

   swings 
  round 
  till 
  the 
  four 
  points 
  once 
  more 
  lie 
  in 
  the 
  same 
  vertical 
  

   plane. 
  The 
  mirror 
  is 
  immersed 
  in 
  petroleum 
  to 
  prevent 
  its 
  swinging 
  

   too 
  freely, 
  and 
  the 
  tilting 
  to 
  which 
  the 
  instrument 
  is 
  subjected 
  is 
  

   registered 
  by 
  means 
  of 
  a 
  ray 
  of 
  light 
  reflected 
  off 
  the 
  mirror 
  on 
  to 
  a 
  

   piece 
  of 
  sensitive 
  paper. 
  

  

  . 
  A 
  description 
  of 
  the 
  effect 
  of 
  the 
  earthquake 
  on 
  this 
  instrument 
  

   has 
  been 
  published 
  by 
  Mr. 
  T. 
  Heath 
  1 
  , 
  along 
  with 
  a 
  reproduction 
  of 
  the 
  

   photographic 
  record. 
  The 
  first 
  indication 
  of 
  disturbance 
  is 
  at 
  

   nh. 
  18m., 
  when 
  very 
  slight 
  preliminary 
  tremors 
  are 
  noticable 
  : 
  

   at 
  nh. 
  28m. 
  more 
  violent 
  oscillations 
  set 
  in 
  and 
  lasted 
  till 
  i2h. 
  

   33m. 
  After 
  this, 
  there 
  is 
  a 
  slight 
  but 
  distinct 
  disturbance 
  at 
  

  

  1 
  Proc. 
  Roy. 
  Soc„ 
  Edin., 
  1897, 
  PP. 
  481-488. 
  

  

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  338 
  ) 
  

  

  