﻿ROTATION 
  OF 
  PILLARS. 
  225 
  

  

  of 
  this 
  : 
  one 
  of 
  the 
  two 
  pillars 
  at 
  Inglis 
  bungalow, 
  Cherrapunji, 
  and 
  a 
  

   more 
  striking 
  one 
  in 
  the 
  old 
  cemetery 
  at 
  Gauhati. 
  In 
  both 
  these 
  

   cases 
  it 
  is 
  to 
  be 
  noticed 
  that 
  the 
  height 
  of 
  the 
  centre 
  of 
  gravity 
  of 
  

   the 
  displaced 
  portion 
  above 
  the 
  plane 
  of 
  fracture 
  is 
  smaller 
  in 
  the 
  

   case 
  of 
  one 
  direction 
  of 
  rotation 
  than 
  of 
  the 
  other. 
  

  

  Now, 
  in 
  the 
  explanation 
  it 
  was 
  assumed 
  that 
  the 
  column 
  once 
  

   tilted 
  on 
  to 
  1 
  would 
  remain 
  so 
  till 
  the 
  motion 
  of 
  the 
  wave 
  particle 
  

   ceased 
  at 
  2, 
  and 
  the 
  return 
  movement 
  from 
  2 
  to 
  3 
  set 
  in. 
  This 
  

   would 
  generally 
  be 
  the 
  case, 
  but 
  the 
  smaller 
  the 
  ^height 
  of 
  the 
  

   displaced 
  portion, 
  the 
  more 
  quickly 
  will 
  it 
  recover 
  its 
  position 
  

   of 
  stability, 
  and 
  the 
  less 
  easily 
  will 
  it 
  be 
  displaced, 
  for 
  the 
  same 
  

   section 
  of 
  base. 
  As 
  a 
  consequence 
  there 
  comes 
  a 
  stage 
  at 
  

   which, 
  as 
  the 
  height 
  of 
  the 
  displaced 
  part 
  diminishes, 
  it 
  will 
  only 
  

   be 
  tilted 
  as 
  the 
  wave 
  particle 
  attains 
  its 
  maximum 
  acceleration, 
  which 
  

   may 
  be 
  put 
  at 
  about 
  one-quarter 
  of 
  its 
  path 
  from 
  1 
  to 
  2. 
  Before 
  

   the 
  wave 
  particle 
  has 
  reached 
  2, 
  the 
  displaced 
  part 
  will 
  have 
  fallen 
  

   down 
  into 
  its 
  base 
  again, 
  retaining 
  what 
  positive 
  rotation 
  it 
  may 
  have 
  

   acquired 
  owing 
  to 
  the 
  gradual 
  change 
  of 
  direction 
  of 
  the 
  path 
  of 
  the 
  

   wave 
  particle, 
  or 
  to 
  the 
  direction 
  of 
  this 
  with 
  regard 
  to 
  the 
  diagonals 
  

   of 
  the 
  rotated 
  portion 
  and 
  by 
  a 
  repetition 
  of 
  this 
  process 
  acquire 
  a 
  

   gradually 
  increasing 
  angular 
  displacement 
  in 
  a 
  positive 
  direction. 
  ■ 
  

  

  But 
  there 
  would 
  almost 
  certainly 
  be 
  more 
  than 
  this. 
  Instead 
  of 
  

   merely 
  falling 
  into 
  its 
  base 
  the 
  displaced 
  part 
  would 
  probably 
  be 
  

   tilted 
  up, 
  by 
  its 
  momentum, 
  in 
  the 
  direction 
  of 
  2, 
  or 
  of 
  somewhat 
  

   towards 
  5 
  from 
  2, 
  before 
  the 
  wave 
  particle 
  reached 
  2. 
  It 
  would 
  then 
  

   be 
  subjected 
  to 
  a 
  displacement 
  due 
  to 
  the 
  movement 
  from 
  2 
  to 
  3, 
  

   that 
  is 
  to 
  say, 
  it 
  would 
  be 
  rotated 
  in 
  a 
  positive 
  direction, 
  or 
  the 
  

   opposite 
  to 
  that 
  which 
  would 
  be 
  impressed 
  on 
  it 
  if 
  it 
  had 
  been 
  tilted 
  

   towards 
  1 
  while 
  being 
  acted 
  on 
  by 
  the 
  movement 
  from 
  2 
  to 
  3. 
  

  

  From 
  this 
  we 
  see 
  that 
  the 
  direction 
  in 
  which 
  the 
  displaced 
  part 
  

   will 
  be 
  rotated 
  depends 
  not 
  only 
  on 
  the 
  relation 
  between 
  the 
  width 
  

   of, 
  and 
  the 
  height 
  of 
  its 
  centre 
  of 
  gravity 
  from, 
  its 
  base, 
  but 
  also 
  

   on 
  its 
  absolute 
  dimensions. 
  In 
  other 
  words, 
  it 
  depends 
  on 
  the 
  quick- 
  

   ness 
  of 
  recovery 
  of 
  the 
  displaced 
  portion 
  when 
  tilted. 
  It 
  has 
  not 
  

   Q 
  ( 
  225 
  ) 
  

  

  