﻿THE 
  UNFELT 
  EARTHQUAKE. 
  

  

  243 
  

  

  

  Interval 
  

   in 
  

  

  minutes. 
  

  

  APPARENT 
  RATE 
  OF 
  TRAVEL 
  ALONG 
  

  

  

  Surface. 
  

  

  Direct 
  Line. 
  

  

  

  Miles 
  p 
  r 
  

   minute. 
  

  

  Kilometres 
  

   per 
  second. 
  

  

  Miles 
  per 
  

   minute. 
  

  

  Kilometres 
  

   per 
  second. 
  

  

  Padua 
  .... 
  

   Siena 
  .... 
  

   Pavia 
  «... 
  

  

  37*5 
  

  

  4075 
  

  

  119 
  

   108 
  

   112 
  

  

  3'»4 
  

   284 
  

   2-97 
  

  

  113 
  

  

  104 
  

  

  106 
  

  

  2*98 
  

   275 
  

  

  2'8l 
  

  

  Arithmetical 
  mean 
  . 
  

  

  38-8 
  

  

  115 
  

  

  3*03 
  109 
  

  

  2-88 
  

  

  The 
  important 
  and 
  striking 
  fact 
  in 
  this 
  table 
  is 
  that 
  we 
  obtain 
  

   a 
  rate 
  of 
  propagation 
  which 
  is 
  almost 
  identical 
  with 
  that 
  deduced 
  in 
  

   Chapter 
  III 
  as 
  the 
  probable 
  rate 
  of 
  travel 
  of 
  the 
  sensible 
  earthquake. 
  

  

  If 
  instead 
  of 
  the 
  time 
  of 
  commencement 
  we 
  take 
  that 
  of 
  maximum 
  

   movement, 
  and 
  take, 
  as 
  we 
  may 
  well 
  do, 
  the 
  origin 
  of 
  these 
  

   cases 
  to 
  be 
  one 
  minute 
  later 
  than 
  the 
  earlier 
  ones, 
  we 
  get 
  very 
  

   slightly 
  a 
  slower 
  rate 
  of 
  propogation 
  as 
  shown 
  in 
  the 
  following 
  

   table 
  :— 
  

  

  

  Interval 
  in 
  

   minutes. 
  

  

  APPARENT 
  RATE 
  OFTRAVEL 
  ALONG 
  

  

  

  Surface. 
  

  

  Direct 
  line. 
  

  

  

  Miles 
  per 
  

   minute. 
  

  

  Kilometres 
  

   per 
  second. 
  

  

  Miles 
  per 
  

   minute. 
  

  

  Kilometres 
  

   per 
  second. 
  

  

  Ischia 
  • 
  

  

  41*0 
  

  

  107 
  

  

  283 
  

  

  IOI 
  

  

  2*69 
  

  

  Catania 
  .... 
  

  

  42 
  'o 
  . 
  

  

  105 
  

  

  278 
  

  

  loo 
  

  

  2*64 
  

  

  Rome, 
  Rocca 
  di 
  Papa 
  

  

  40'75 
  

  

  109 
  

  

  2-88 
  

  

  103 
  

  

  272 
  

  

  ,, 
  Ufficio 
  centrale 
  

  

  41*0 
  

  

  108 
  

  

  2-85 
  

  

  102 
  

  

  271 
  

  

  Padua 
  • 
  . 
  . 
  . 
  

  

  41 
  "25 
  

  

  108 
  

  

  2*86 
  

  

  102 
  

  

  271 
  

  

  Siena 
  .... 
  

  

  42'0 
  

  

  107 
  

  

  2*84 
  

  

  1 
  02 
  

  

  2*69 
  

  

  Pavia 
  .... 
  

  

  42*0 
  

  

  109 
  

  

  2-89 
  

  

  103 
  

  

  273 
  

  

  Arithmetical 
  mean 
  . 
  

  

  4i'5 
  

  

  107 
  

  

  2-84 
  

  

  102 
  

  

  270 
  

  

  Before 
  considering 
  the 
  meaning 
  of 
  these 
  results, 
  a 
  short 
  digression 
  

  

  ( 
  249 
  ) 
  

  

  