﻿APPENDIX 
  C. 
  353 
  

  

  The 
  difficulty 
  is 
  far 
  greater 
  when 
  we 
  consider 
  the 
  case 
  of 
  the 
  projected 
  stones 
  

   near 
  Rambrai. 
  Taking 
  the 
  maximum 
  velocity 
  at 
  16 
  ft. 
  per 
  sec. 
  and 
  the 
  ampli- 
  

   tude 
  as 
  i 
  foot, 
  which 
  may 
  be 
  regarded 
  as 
  certainly 
  in 
  excess 
  of 
  the 
  amplitude 
  of 
  

   the 
  wave 
  motion, 
  we 
  obtain 
  the 
  incredible 
  result 
  that 
  the 
  maximum 
  acceleration 
  

   was 
  256 
  feet 
  per 
  sec. 
  per 
  sec. 
  In 
  other 
  words 
  the 
  violence 
  of 
  the 
  shock 
  was 
  eoui- 
  

   valent 
  to 
  that 
  of 
  sudden 
  arrest 
  after 
  a 
  fall 
  from 
  a 
  height 
  of 
  1024 
  feet. 
  Even 
  ir 
  we 
  

   take 
  the 
  impossible 
  amplitude 
  of 
  2 
  feet, 
  involving 
  a 
  backward 
  and 
  forward 
  move- 
  

   ment 
  of 
  double 
  this, 
  or 
  4 
  feet, 
  the 
  acceleration 
  is 
  only 
  reduced 
  to 
  128 
  feet 
  per 
  sec. 
  

   per 
  sec. 
  or 
  equivalent 
  to 
  sudden 
  arrest 
  after 
  a 
  fall 
  of 
  256 
  feet. 
  

  

  It 
  must 
  be 
  clearly 
  understood 
  that, 
  if 
  the 
  movement 
  was 
  due 
  to 
  elastic 
  vibra- 
  

   tions 
  or 
  to 
  a 
  wave 
  motion 
  even 
  approximately 
  simulating 
  such, 
  there 
  can 
  be 
  no 
  

   mistake 
  in 
  these 
  figures. 
  The 
  stone 
  was 
  projected 
  through 
  the 
  air 
  a 
  distance 
  of 
  

   8$ 
  ft. 
  horizontally 
  and 
  to 
  enable 
  it 
  to 
  traverse 
  this 
  distance 
  the 
  initial 
  velocity 
  must 
  

   have 
  been 
  at 
  least 
  i6| 
  ft. 
  per 
  sec, 
  and 
  if 
  the 
  direction 
  in 
  which 
  it 
  was 
  projected 
  was 
  

   at 
  an 
  angle 
  much 
  greater, 
  or 
  much 
  less, 
  than 
  45 
  to 
  the 
  horizontal 
  the 
  velocity 
  must 
  

   have 
  been 
  even 
  greater. 
  

  

  Knowing 
  the 
  maximum 
  velocity 
  of 
  wave 
  particle, 
  and 
  the 
  amplitude 
  of 
  the 
  

   wave 
  motion, 
  the 
  maximum 
  acceleration 
  can 
  be 
  infallibly 
  calculated 
  ; 
  but 
  we 
  have 
  

   seen 
  that 
  even 
  assuming 
  an 
  impossibly 
  great 
  amplitude 
  we 
  obtain 
  an 
  incredible 
  

   acceleration. 
  Where 
  then 
  is 
  the 
  error 
  ? 
  Evidently 
  in 
  the 
  assumption 
  that 
  the 
  

   high 
  velocities 
  determined 
  were 
  those 
  of 
  wave 
  mction. 
  

  

  The 
  results 
  of 
  the 
  revision 
  of 
  the 
  great 
  triangulation 
  in 
  the 
  Khasi 
  hills 
  show 
  

   that 
  there 
  have 
  been 
  considerable 
  changes, 
  both 
  horizontal 
  and 
  vertical, 
  in 
  

   the 
  positions 
  of 
  the 
  stations 
  ; 
  yet 
  the 
  chain 
  of 
  triangles 
  lay 
  near 
  the 
  outskirts 
  cf 
  

   the 
  epicentral 
  tract, 
  where 
  displacements 
  might 
  be 
  expected 
  to 
  be 
  at 
  their 
  mini- 
  

   mum. 
  The 
  observations 
  recorded 
  in 
  Chapter 
  IX 
  show 
  that 
  there 
  have 
  been 
  

   differential 
  movements 
  approaching 
  40 
  feet 
  in 
  vertical 
  height 
  in 
  parts 
  of 
  the 
  

   epicentral 
  tract, 
  and 
  it 
  is 
  conceivable 
  that 
  in 
  places 
  the 
  actual 
  changes 
  in 
  height 
  

   and 
  position 
  have 
  been 
  far 
  beyond 
  those 
  which 
  have 
  been 
  measured 
  as 
  yet. 
  This 
  

   being 
  so 
  we 
  would 
  have, 
  in 
  the 
  epicentral 
  tract, 
  bodily 
  displacement 
  of 
  the 
  ground, 
  

   apart 
  from 
  true 
  wave 
  motion, 
  which 
  would 
  probably 
  take 
  place 
  by 
  a 
  series 
  of 
  

   jerks, 
  but 
  might 
  have 
  been 
  a 
  simple 
  and{single 
  movement. 
  

  

  To 
  take 
  the 
  case 
  of 
  Rambrai, 
  if 
  we 
  assume 
  that 
  there 
  was 
  a 
  permanent 
  

   displacement 
  of 
  the 
  ground 
  of 
  only 
  16 
  feet, 
  and 
  that 
  the 
  movement 
  was 
  approxi- 
  

   mately 
  harmonic 
  in 
  its 
  character, 
  i.e., 
  beginning 
  slowly, 
  gradually 
  increasing 
  in 
  

   rapidity 
  and 
  then 
  gradually 
  dying 
  out, 
  then 
  the 
  required 
  velocity 
  of 
  16 
  feet 
  per 
  

   sec. 
  would 
  only 
  involve 
  a 
  maximum 
  acceleration 
  of 
  32 
  feet 
  per 
  sec. 
  per 
  sec. 
  That 
  

   the 
  acceleration 
  was 
  at 
  least 
  this 
  much 
  we 
  know 
  from 
  the 
  fact 
  that, 
  in 
  order 
  to 
  

   account 
  for 
  the 
  projection 
  of 
  this 
  block 
  of 
  stone, 
  the 
  vertical 
  acceleration 
  must 
  

   have 
  been 
  at 
  least 
  32 
  feet 
  per 
  sec. 
  per 
  sec. 
  and 
  the 
  maximum 
  acceleration 
  in 
  the 
  

   ground 
  consequently 
  greater 
  than 
  this. 
  

  

  From 
  this 
  it 
  will 
  be 
  seen 
  that 
  the 
  high 
  velocities 
  of 
  movement 
  which 
  were 
  de- 
  

   veloped 
  in 
  the 
  epicentral 
  tract 
  cannot 
  be 
  ascribed 
  to 
  the 
  wave 
  motion 
  proper, 
  set 
  

   up 
  by 
  the 
  earthquake, 
  but 
  must 
  be 
  attributed 
  to 
  those 
  bodily 
  displacements 
  in 
  the 
  

   earth's 
  crust 
  which 
  were 
  the 
  primary 
  cause 
  of 
  the 
  earthquake. 
  In 
  other 
  words, 
  

  

  2 
  A 
  ( 
  353 
  ) 
  

  

  