﻿APPENDIX 
  tt. 
  37 
  1 
  

  

  exceeded 
  gft. 
  With 
  about 
  the 
  same 
  length 
  of 
  triangles 
  we 
  have 
  in 
  the 
  case 
  of 
  the 
  

   1897 
  shock 
  a 
  maximum 
  displacement 
  calculated 
  at 
  12ft. 
  As 
  has 
  been 
  explained, 
  

   there 
  is 
  some 
  uncertainty 
  about 
  the 
  basis 
  of 
  this 
  calculation, 
  and 
  if 
  the 
  explanation 
  

   offered 
  above 
  is 
  the 
  true 
  one, 
  this 
  figure 
  requires 
  modification, 
  but 
  whether 
  the 
  

   maximum 
  displacement 
  would 
  be 
  in 
  excess 
  or 
  defect 
  of 
  it, 
  cannot 
  be 
  decided 
  in 
  the 
  

   absence 
  of 
  detailed 
  calculations. 
  In 
  any 
  case 
  it 
  seems 
  certain 
  that 
  the 
  amount 
  

   hiust 
  have 
  been 
  considerably 
  in 
  excess 
  of 
  5ft., 
  and 
  it 
  must 
  be 
  further 
  borne 
  in 
  

   mind 
  that 
  this 
  triangulation 
  lies 
  near 
  the 
  limit 
  of 
  the 
  epifocal 
  area, 
  and 
  far 
  removed 
  

   From 
  the 
  part 
  where 
  displacements 
  were 
  at 
  their 
  maximum. 
  

  

  Appendix 
  H. 
  

  

  A 
  Review 
  of 
  the 
  extent 
  of 
  the 
  Lisbon 
  Earthquake 
  of 
  1st 
  November 
  

   17 
  S5) 
  as 
  compared 
  with 
  that 
  of 
  the 
  Great 
  Earthquake 
  of 
  12th 
  

   June 
  i8gy. 
  

  

  In 
  a 
  preliminary 
  note 
  on 
  the 
  earthquake, 
  written 
  six 
  weeks 
  after 
  the 
  event, 
  I 
  

   referred 
  to 
  it 
  as 
  ' 
  Unsurpassed 
  by 
  any 
  since 
  the 
  great 
  Lisbon 
  earthquake 
  of 
  1st 
  

   November 
  1755, 
  and 
  rivalling 
  this 
  in 
  magnitude 
  of 
  the 
  area 
  over 
  which 
  it 
  was 
  felt; 
  

   surpassing 
  it 
  indeed, 
  if 
  we 
  exclude 
  the 
  doubtful 
  records 
  of 
  the 
  earlier 
  shock.' 
  

  

  This 
  statement 
  excited 
  surprise 
  and 
  was 
  even 
  called 
  to 
  question 
  in 
  the 
  press* 
  

   yet 
  a 
  fuller 
  knowledge 
  of 
  the 
  extent 
  of 
  the 
  earthquake 
  of 
  1897 
  has 
  borne 
  it 
  out. 
  

   The 
  surprise 
  was 
  a 
  natural 
  outcome 
  of 
  the 
  very 
  exaggerated 
  ideas 
  of 
  the 
  extent 
  

   of 
  the 
  Lisbon 
  earthquake 
  which 
  are 
  to 
  be 
  found 
  repeated 
  from 
  one 
  text 
  book 
  to 
  

   another 
  without 
  verification. 
  I 
  have 
  thought 
  it 
  desirable, 
  on 
  this 
  account, 
  to 
  

   append 
  a 
  short 
  review 
  of 
  what 
  is 
  known 
  of 
  the 
  extent 
  over 
  which 
  the 
  Lisbon 
  shock 
  

   was 
  felt. 
  

  

  To 
  begin 
  with, 
  no 
  comparison 
  of 
  violence 
  is 
  possible. 
  The 
  data 
  in 
  the 
  case 
  of 
  

   the'Lisbon 
  shock 
  are 
  altogether 
  too 
  imperfect 
  to 
  permit 
  of 
  this, 
  nor 
  is 
  it 
  of 
  import- 
  

   ance 
  in 
  determining 
  the 
  relative 
  magnitude 
  of 
  the 
  two 
  shocks. 
  Some 
  earth- 
  

   quakes, 
  it 
  is 
  known, 
  may, 
  like 
  those 
  of 
  Ischia, 
  have 
  a 
  great 
  local 
  violence 
  but 
  very 
  

   small 
  extent, 
  yet 
  it 
  would 
  be 
  absurd 
  to 
  speak 
  of 
  these 
  as 
  of 
  greater 
  magnitude 
  

   than 
  others 
  which, 
  though 
  nowhere 
  rising 
  to 
  the 
  same 
  degree 
  of 
  violence, 
  are 
  felt 
  

   over 
  a 
  kingdom 
  or 
  two. 
  

  

  The 
  only 
  strictly 
  scientific 
  comparison 
  of 
  two 
  shocks 
  would 
  be 
  a 
  comparison 
  

   of 
  the 
  energy 
  developed 
  in 
  each. 
  This 
  measurement 
  is 
  unfortunately 
  still 
  im- 
  

   possible, 
  but 
  there 
  is 
  good 
  reason 
  to 
  suppose 
  that 
  is 
  approximately 
  proportional 
  to 
  

   the 
  area 
  over 
  which 
  they 
  are 
  felt. 
  Any 
  way 
  this 
  is 
  the 
  only 
  possible 
  means 
  of 
  

   comparison 
  in 
  the 
  present 
  state 
  of 
  seismology, 
  and 
  as 
  the 
  results 
  it 
  leads 
  to 
  are 
  

   at 
  any 
  rate 
  approximately 
  true, 
  it 
  is 
  the 
  one 
  that 
  I 
  have 
  adopted. 
  

  

  Before 
  instituting 
  a 
  comparison 
  it 
  is' 
  necessary 
  to 
  have 
  a 
  clear 
  conception 
  of 
  

   what 
  is 
  meant 
  by 
  the 
  area 
  over 
  which 
  the 
  shock 
  was 
  felt. 
  The 
  Lisbon 
  earth- 
  

   quake 
  originated 
  under 
  the 
  sea 
  and 
  set 
  up 
  large 
  sea-waves, 
  to 
  which 
  much 
  of 
  the 
  

   loss 
  of 
  life 
  in 
  Lisbon 
  was 
  due, 
  and 
  these 
  waves 
  were 
  observed 
  everywhere 
  along 
  

   the 
  Atlantic 
  coasts, 
  even 
  to 
  the 
  Weat 
  Indies. 
  Yet 
  it 
  would 
  be 
  altogether 
  mislead- 
  

  

  ( 
  37' 
  ) 
  

  

  