﻿APPENDIX 
  D. 
  

  

  357 
  

  

  

  

  

  Overthrow 
  

  

  

  Nature 
  of 
  object 
  and 
  reference 
  

  

  , 
  

  

  or 
  

  

  Azimuth. 
  

  

  

  

  

  projection. 
  

  

  

  Sylhet 
  — 
  

  

  

  

  

  

  Gate 
  pillar 
  near 
  Government 
  School 
  

  

  . 
  

  

  p. 
  274 
  . 
  

  

  O 
  

  

  40 
  

  

  „ 
  „ 
  Deputy 
  Commissioner's 
  bung 
  

  

  alow 
  p. 
  274 
  • 
  

  

  O 
  

  

  

  

  Tomb 
  in 
  cemetery 
  • 
  • 
  

  

  . 
  

  

  p. 
  274 
  . 
  

  

  O 
  

  

  155 
  

  

  „ 
  of 
  Ensign 
  Spooner 
  . 
  . 
  

  

  • 
  

  

  P- 
  275 
  ■ 
  

  

  

  

  90 
  

  

  Brick 
  pillar 
  .... 
  

  

  • 
  

  

  P- 
  275 
  • 
  

  

  

  

  1 
  So 
  

  

  - 
  Square 
  column 
  

  

  . 
  

  

  P- 
  275 
  • 
  

  

  

  

  225 
  

  

  Gate 
  pillar, 
  New 
  Hospital 
  

  

  . 
  

  

  p. 
  276 
  . 
  

  

  

  

  288 
  

  

  „ 
  , 
  Church 
  . 
  

  

  , 
  , 
  

  

  p. 
  276 
  . 
  

  

  

  

  

  

  Do. 
  

  

  , 
  

  

  p. 
  276 
  . 
  

  

  

  

  250 
  

  

  Vertical 
  boiler 
  • 
  

  

  • 
  

  

  p. 
  276 
  . 
  

  

  

  

  240 
  

  

  In 
  the 
  early 
  days 
  of 
  the 
  modern 
  development 
  of 
  seismology, 
  great 
  importance 
  

   was 
  attached 
  to 
  the 
  direction 
  of 
  overthrow 
  of 
  free 
  falling 
  objects, 
  as 
  a 
  means 
  of 
  

   determining 
  the 
  position 
  of 
  the 
  epicentre 
  and 
  hence 
  of 
  the 
  focus. 
  This 
  method 
  was 
  

   employed 
  by 
  Mr. 
  R. 
  Mallet, 
  in 
  the 
  case 
  of 
  the 
  Neapolitan 
  earthquake 
  of 
  1857 
  

   with 
  a 
  concordance 
  in 
  the 
  intersection 
  of 
  the 
  lines 
  of 
  direction 
  obtained, 
  so 
  

   conspicuous 
  as 
  to 
  give 
  great 
  support 
  to 
  the 
  supposition 
  on 
  which 
  the 
  method 
  was 
  

   based. 
  In 
  the 
  case 
  of 
  subsequent 
  earthquakes, 
  however, 
  the 
  method 
  has 
  not 
  been 
  

   found 
  so 
  successful, 
  and 
  with 
  the 
  growth 
  of 
  a 
  more 
  accurate 
  knowledge 
  of 
  the 
  

   true 
  nature 
  of 
  earthquake 
  motion, 
  as 
  derived 
  from 
  the 
  labours 
  of 
  the 
  band 
  of 
  

   workers 
  in 
  Japan 
  who 
  have 
  practically 
  revolutionised 
  seismology, 
  the 
  method 
  has 
  

   become 
  discredited. 
  

  

  It 
  was 
  found 
  that 
  instead 
  of 
  being 
  a 
  simple 
  to 
  and 
  fro 
  motion, 
  the 
  motion 
  of 
  

   the 
  wave 
  particle 
  was 
  extremely 
  complicated, 
  and 
  that, 
  in 
  the 
  case 
  of 
  moderate 
  

   earthquakes, 
  the 
  maximum 
  movement 
  was 
  by 
  no 
  means 
  always 
  or 
  even 
  usually 
  

   in 
  the 
  direction 
  of 
  the 
  propagation 
  of 
  the 
  earthquake 
  wave, 
  but 
  might 
  be 
  at 
  any 
  

   angle 
  with 
  it. 
  Assuming 
  that 
  the 
  same 
  held 
  good 
  of 
  more 
  violent 
  earthquakes 
  

   it 
  was 
  evident 
  that 
  the 
  direction 
  of 
  overthrow 
  would 
  only 
  exceptionally 
  be 
  that 
  

   of 
  the 
  propagation 
  of 
  the 
  earthquake 
  wave, 
  and 
  would 
  consequently 
  generally 
  

   point 
  in 
  any 
  direction 
  except 
  that 
  of 
  the 
  seismic 
  vertical. 
  

  

  Against 
  this 
  there 
  has 
  always 
  stood 
  the 
  case 
  of 
  the 
  Neapolitan 
  earthquake 
  

   where 
  the 
  direction 
  of 
  overthrow 
  in 
  the 
  vast 
  majority 
  of 
  cases 
  pointed 
  to 
  the 
  

   epicentre, 
  and 
  it 
  has 
  long 
  seemed 
  to 
  the 
  writer 
  that 
  the 
  assumption, 
  that 
  the 
  

   nature 
  of 
  the 
  movement 
  in 
  violent 
  and 
  in 
  moderate 
  earthquakes 
  was 
  similar, 
  went 
  

   too 
  far. 
  It 
  is 
  conceivable 
  that, 
  within 
  the 
  limits 
  where 
  the 
  shock 
  has 
  still 
  power 
  to 
  

   cause 
  the 
  overthrow 
  of 
  gate 
  pillars, 
  etc., 
  the 
  one 
  or 
  two 
  vibrations, 
  which 
  alone 
  have 
  

   this 
  power, 
  should 
  be 
  directly 
  or 
  nearly 
  directly 
  outwards 
  from 
  the 
  centre, 
  while 
  

   further 
  away 
  this 
  relationship 
  might 
  c-iase 
  to 
  hold 
  good. 
  

  

  An 
  examination 
  of 
  the 
  tabulated 
  directions 
  of 
  overthrow 
  and 
  projection 
  lends 
  

   some 
  support 
  to 
  this 
  supposition. 
  At 
  places 
  like 
  Shillong, 
  which 
  were 
  within 
  the 
  

   limits 
  of 
  the 
  epicentre, 
  or, 
  like 
  Gauhati, 
  which 
  were 
  close 
  to 
  it, 
  there 
  is 
  no 
  uniformity 
  

  

  C 
  357 
  ) 
  

  

  