﻿ROTATION 
  OF 
  PILLARS, 
  2oj 
  

  

  hardly 
  be 
  other 
  than 
  seismic, 
  using 
  the 
  word 
  in 
  its 
  widest 
  sense 
  ; 
  that 
  

   is 
  to 
  say, 
  the 
  sounds 
  are 
  due 
  to 
  disturbances 
  in 
  the 
  interior 
  of 
  the 
  

   earth, 
  caused 
  by 
  readjustments 
  of 
  the 
  distribution 
  of 
  the 
  material 
  

   of 
  its 
  crust, 
  and 
  taking 
  the 
  form 
  of 
  elastic 
  vibrations, 
  which 
  are 
  trans- 
  

   mitted 
  to 
  the 
  surface 
  and 
  there 
  become 
  sensible 
  as 
  sounds. 
  

  

  Chapter 
  XIV.— 
  THE 
  ROTATION 
  OF 
  PILLARS 
  AND 
  

   MONUMENTS. 
  

  

  That 
  pillars 
  and 
  other 
  similar 
  objects 
  may 
  be 
  left 
  standing, 
  but 
  

   with 
  one 
  part 
  twisted 
  round 
  upon 
  another, 
  has 
  long 
  been 
  known 
  

   as 
  a 
  fantastic 
  effect 
  of 
  severe 
  earthquakes, 
  and 
  even 
  in 
  some 
  cases 
  

   of 
  earthquakes 
  which 
  can 
  hardly 
  be 
  called 
  severe. 
  There 
  has, 
  

   however, 
  been 
  no 
  instance 
  where 
  cases 
  of 
  this 
  kind 
  have 
  been 
  so 
  

   numerous, 
  and 
  so 
  various 
  in 
  the 
  nature 
  of 
  the 
  objects 
  rotated, 
  as 
  

   the 
  earthquake 
  now 
  under 
  consideration, 
  and 
  advantage 
  has 
  been 
  

   taken 
  of 
  this 
  to 
  collect 
  all 
  the 
  information 
  possible, 
  and 
  to 
  apply 
  

   the 
  data 
  so 
  obtained 
  in 
  testing 
  the 
  sufficiency 
  of 
  the 
  various 
  theories 
  

   which 
  have 
  been 
  advanced 
  by 
  different 
  authors 
  to 
  account 
  for 
  the 
  

   phenomenon. 
  

  

  In 
  treating 
  this 
  branch 
  of 
  the 
  investigation 
  of 
  the 
  earthquake, 
  

   I 
  shall 
  first 
  of 
  all 
  describe 
  those 
  instances 
  of 
  rotation 
  which 
  have 
  

   come 
  under 
  my 
  observation, 
  and 
  then 
  proceed 
  to 
  an 
  examination 
  of 
  

   the 
  theories 
  which 
  have 
  been 
  advanced. 
  

  

  The 
  description, 
  however, 
  requires 
  a 
  few 
  words 
  of 
  introduction. 
  

   In 
  order 
  to 
  determine 
  exactly 
  what 
  has 
  happened 
  we 
  require 
  to 
  

   know 
  (i) 
  the 
  amount 
  of 
  the 
  twisting, 
  (2) 
  its 
  direction, 
  and 
  (3) 
  the 
  

   amount 
  and 
  direction 
  of 
  the 
  lateral 
  displacement 
  of 
  the 
  upper 
  por- 
  

   tion 
  as 
  a 
  whole, 
  that 
  is 
  to 
  say 
  the 
  distance 
  and 
  direction 
  that 
  its 
  

   centre 
  of 
  gravity 
  now 
  lies 
  with 
  regard 
  to 
  its 
  position 
  before 
  the 
  earth- 
  

   quake. 
  The 
  first 
  and 
  third 
  of 
  these 
  require 
  no 
  explanation, 
  but 
  the 
  

   second 
  is 
  one 
  in 
  which 
  confusion 
  is 
  possible 
  ; 
  in 
  the 
  case 
  for 
  instance 
  

   of 
  a 
  square 
  pillar 
  whose 
  sides 
  now 
  stand 
  at 
  an 
  angle 
  of 
  40 
  with 
  their 
  

   original 
  direction 
  it 
  is 
  obviously 
  important 
  to 
  know 
  whether 
  it 
  has 
  

  

  ( 
  207 
  ) 
  

  

  