﻿Miscellaneous 
  Intelligence. 
  309 
  

  

  sound 
  should 
  be 
  the 
  most 
  prominent 
  feature 
  ; 
  with 
  very 
  strong 
  

   ones 
  the 
  sound, 
  though 
  actually 
  louder, 
  should 
  be 
  relatively 
  insig- 
  

   nificant 
  ; 
  and 
  when, 
  as 
  in 
  the 
  Hereford 
  earthquake, 
  the 
  earthquake 
  

   consists 
  of 
  two 
  distinct 
  parts, 
  the 
  two 
  shocks 
  may 
  differ 
  widely 
  

   in 
  intensity, 
  while 
  the 
  accompanying 
  sounds 
  may 
  be 
  almost 
  equally 
  

   loud. 
  

  

  With 
  observers 
  of 
  given 
  average 
  auditory 
  powers, 
  the 
  magni- 
  

   tude 
  of 
  the 
  sound-area 
  depends 
  on 
  the 
  limited 
  strength 
  of 
  the 
  

   marginal 
  vibrations, 
  and 
  on 
  the 
  dimensions 
  of 
  the 
  seismic 
  focus, 
  

   and 
  therefore 
  of 
  its 
  marginal 
  regions. 
  The 
  magnitude 
  of 
  the 
  

   disturbed 
  area 
  depends 
  partly 
  on 
  the 
  size 
  of 
  the 
  focus, 
  chiefly 
  

   perhaps 
  on 
  the 
  initial 
  intensity 
  of 
  the 
  vibrations 
  from 
  its 
  central 
  

   portion. 
  While 
  the 
  dimensions 
  of 
  the 
  sound-area 
  should 
  gener- 
  

   ally 
  increase 
  with 
  those 
  of 
  the 
  disturbed 
  area, 
  it 
  is 
  evident 
  that 
  they 
  

   should 
  not 
  increase 
  in 
  the 
  same 
  ratio. 
  With 
  very 
  strong 
  shocks, 
  

   the 
  sound-area 
  should 
  be 
  a 
  comparatively 
  small 
  district 
  surround- 
  

   ing 
  the 
  epicentre. 
  With 
  very 
  slight 
  ones, 
  the 
  marginal 
  regions 
  

   would 
  be 
  so 
  great 
  compared 
  with 
  the 
  central 
  portion 
  of 
  the 
  focus, 
  

   that 
  the 
  sound-area 
  might 
  overlap 
  the 
  disturbed 
  area. 
  In 
  the 
  

   limit, 
  the 
  central 
  portion 
  of 
  the 
  focus 
  would 
  vanish, 
  and 
  an 
  earth- 
  

   sound 
  would 
  be 
  the 
  only 
  result 
  sensible 
  to 
  human 
  beings.* 
  

  

  Several 
  of 
  the 
  phenomena 
  of 
  earthquake-sounds 
  depend 
  on 
  the 
  

   superficial 
  form 
  and 
  inclined 
  position 
  of 
  the 
  focus, 
  and 
  on 
  the 
  

   fact 
  that 
  the 
  most 
  sensible 
  sound-vibrations 
  come 
  from 
  the 
  upper 
  

   and 
  lateral 
  margins. 
  The 
  isacoustic 
  lines 
  and 
  the 
  boundary 
  

   of 
  the 
  sound-area 
  should 
  not 
  be 
  concentric 
  with 
  the 
  isoseismal 
  

   lines. 
  Relatively 
  to 
  the 
  latter 
  the 
  sound-area 
  will 
  be 
  shifted 
  

   towards 
  the 
  fault-line, 
  and 
  also 
  in 
  a 
  direction 
  parallel 
  to 
  it, 
  if 
  one 
  

   lateral 
  margin 
  should 
  predominate 
  over 
  the 
  other. 
  

  

  The 
  time-relations 
  of 
  the 
  sound 
  and 
  shock 
  remain 
  to 
  be 
  con- 
  

   sidered. 
  The 
  sound-vibrations 
  from 
  the 
  margin 
  nearest 
  to 
  the 
  

   observer 
  should 
  be 
  heard 
  before 
  the 
  shock 
  begins, 
  those 
  from 
  the 
  

   upper 
  margin, 
  and 
  possibly 
  from 
  parts 
  of 
  the 
  central 
  portion, 
  dur- 
  

   ing 
  the 
  progress 
  of 
  the 
  shock, 
  and 
  those 
  from 
  the 
  furthest 
  margin 
  

   after 
  the 
  shock 
  ends. 
  Moreover, 
  the 
  sound-vibrations 
  from 
  the 
  

   nearer 
  lateral 
  margin 
  will 
  be 
  of 
  greater 
  intensity 
  than 
  those 
  from 
  

   the 
  further 
  one 
  ; 
  and 
  thus 
  the 
  fore-sound 
  should 
  be 
  more 
  generally 
  

   heard 
  than 
  the 
  after-sound, 
  and 
  with 
  Japanese 
  and 
  some 
  other 
  

   observers 
  should 
  be 
  the 
  only 
  one 
  perceptible. 
  The 
  percentage 
  

   of 
  observations 
  of 
  the 
  after-sound 
  should 
  also 
  diminish 
  with 
  the 
  

   increasing 
  distance 
  from 
  the 
  origin 
  ; 
  and 
  the 
  duration 
  of 
  the 
  

   sound, 
  especially 
  near 
  the 
  epicentre, 
  should 
  be 
  greater 
  than 
  that 
  

   of 
  the 
  shock. 
  

  

  At 
  places 
  near 
  the 
  epicentre, 
  and 
  also 
  at 
  the 
  places 
  whose 
  dis- 
  

   tances 
  are 
  great 
  compared 
  with 
  the 
  dimensions 
  of 
  the 
  focus, 
  the 
  

   sound-vibrations 
  which 
  appear 
  loudest 
  will 
  be 
  those 
  which 
  origi- 
  

  

  * 
  It 
  has 
  been 
  suggested 
  that 
  the 
  comparative 
  smallness 
  of 
  the 
  sound-area 
  may- 
  

   be 
  due 
  to 
  the 
  more 
  rapid 
  extinction 
  of 
  the 
  sound-vibrations 
  ; 
  but 
  the 
  explanation 
  

   is 
  clearly 
  incomplete, 
  for 
  it 
  fails 
  in 
  the 
  cases 
  in 
  which 
  the 
  sound-area 
  overlaps 
  the 
  

   disturbed 
  area. 
  

  

  