﻿236 
  OLDHAM: 
  GREAT 
  EARTHQUAKE 
  OF 
  1897. 
  

  

  phase 
  is 
  well 
  marked 
  at 
  nh. 
  25m. 
  44s. 
  on 
  the 
  NE-SW 
  component, 
  

   and 
  at 
  nh.25m. 
  55s. 
  on 
  the 
  NW-SE 
  component, 
  the 
  character 
  

   of 
  the 
  trace 
  becoming 
  more 
  open, 
  and 
  the 
  travel 
  of 
  the 
  pendulum 
  

   bob 
  rises 
  to 
  n 
  mm., 
  the 
  character 
  of 
  the 
  curve 
  indicating 
  oscil- 
  

   lations 
  of 
  the 
  normal 
  period 
  of 
  the 
  pendulum, 
  5'2s., 
  superimposed 
  

   on 
  undulations 
  of 
  longer 
  period. 
  These 
  correspond 
  to 
  the 
  violent 
  

   oscillations 
  of 
  the 
  Padua 
  pendulum 
  between 
  nh. 
  26m. 
  and 
  uh. 
  30m. 
  

   Converted 
  into 
  angular 
  measurement, 
  the 
  excursion 
  of 
  the 
  pendulum 
  

   corresponds 
  to 
  a 
  tilt 
  of 
  10" 
  of 
  arc 
  from 
  the 
  vertical. 
  The 
  larger 
  

   undulations 
  set 
  in 
  about 
  uh. 
  45m.; 
  their 
  maximum 
  is 
  at 
  uh. 
  48m., 
  

   but 
  as 
  the 
  components 
  are 
  NE-SW 
  and 
  NW-SE 
  instead 
  of 
  N-S 
  and 
  

   E-W, 
  the 
  diagram 
  cannot 
  be 
  readily 
  compared 
  with 
  the 
  others, 
  and 
  

   it 
  is 
  possible 
  that 
  the 
  apparently 
  late 
  beginning 
  of 
  these 
  is 
  due 
  

   to 
  the 
  E-W 
  component 
  not 
  showing 
  up 
  as 
  well 
  as 
  it 
  does 
  in 
  the 
  

   other 
  diagrams. 
  The 
  disturbance 
  lasted 
  till 
  about 
  14 
  h. 
  

  

  Siena. 
  — 
  I 
  am 
  indebted 
  to 
  Prof. 
  Silvio 
  Lussana, 
  of 
  the 
  University 
  

   of 
  Siena, 
  for 
  a 
  photograph 
  of 
  the 
  diagram 
  made 
  by 
  his 
  instrument. 
  

   This 
  closely 
  resembles 
  on 
  a 
  small 
  scale 
  that 
  of 
  Prof, 
  Vicentini's 
  

   instrument 
  at 
  Padua. 
  Disturbance 
  commenced 
  at 
  uh. 
  17m. 
  G. 
  M. 
  T„ 
  

   rapidly 
  attained 
  a 
  maximum 
  at 
  ilh. 
  19^ 
  m. 
  and 
  then 
  died 
  down. 
  

   The 
  second 
  phase 
  is 
  marked 
  by 
  an 
  increased 
  displacement 
  from 
  

   26m. 
  to 
  28m., 
  with 
  a 
  maximum 
  at 
  27m., 
  but 
  instead 
  of 
  being 
  

   nearly 
  equal 
  to 
  the 
  original 
  displacement, 
  it 
  does 
  not 
  amount 
  to 
  

   more 
  than 
  one-sixth 
  of 
  it. 
  The 
  trace 
  after 
  this 
  shows 
  a 
  number 
  of 
  

   minute 
  undulations, 
  and 
  at 
  46m. 
  they 
  increase 
  in 
  size, 
  attaining 
  

   their 
  maximum 
  at 
  48 
  m., 
  and 
  then 
  diminishing 
  once 
  more. 
  I 
  have 
  no 
  

   information 
  as 
  to 
  the 
  total 
  duration 
  of 
  the 
  disturbance, 
  

  

  Pavia.— 
  From 
  Dr. 
  Emilio 
  Oddone, 
  of 
  the 
  Royal 
  Meteorological 
  

   and 
  Geodynamical 
  Observatory 
  at 
  Pavia, 
  I 
  have 
  received 
  a 
  tracing 
  

   of 
  the 
  record 
  made 
  by 
  his 
  microseismograph, 
  a 
  simple 
  pendulum 
  

   of 
  4'5m., 
  length, 
  and 
  40kg 
  weight; 
  the 
  movement 
  of 
  the 
  bob 
  

   is 
  magnified 
  ten 
  times, 
  and 
  recorded 
  on 
  a 
  paper 
  moving 
  about 
  10 
  cm. 
  

   per 
  hour. 
  

  

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  236 
  ) 
  

  

  