﻿THE 
  SEISMIC 
  FOCUS. 
  167 
  

  

  being 
  scattered 
  over 
  a 
  large 
  area 
  ; 
  it 
  accounts 
  for 
  the 
  faults, 
  the 
  

   fractures 
  and 
  the 
  local 
  changes 
  of 
  levels 
  ; 
  it 
  accounts, 
  at 
  the 
  same 
  

   time, 
  for 
  the 
  horizontal 
  shiftings 
  which 
  have 
  been 
  observed 
  ; 
  and 
  it 
  

   accounts 
  for 
  the 
  absence 
  of 
  any 
  definite 
  centre 
  of 
  maximum 
  violence 
  

   as 
  well 
  as 
  the 
  existence 
  of 
  several 
  local 
  centres 
  of 
  maximum 
  violence 
  

   within 
  a 
  general 
  central 
  pleistoseismic 
  area. 
  

  

  At 
  the 
  same 
  time, 
  it 
  introduces 
  no 
  condition 
  which 
  is 
  at 
  variance 
  

   with 
  or 
  unsupported 
  by 
  observed 
  facts, 
  and 
  we 
  may 
  safely 
  accept 
  it 
  

   as 
  the 
  true 
  theory 
  of 
  the 
  origin 
  of 
  this 
  earthquake. 
  

  

  Though 
  apparently 
  the 
  most 
  probable, 
  this 
  is 
  not 
  the 
  only 
  possible, 
  

   hypothesis. 
  The 
  surface 
  features 
  of 
  the 
  Assam 
  range, 
  described 
  in 
  

   the 
  last 
  chapter, 
  are 
  compatible 
  with, 
  in 
  some 
  respects 
  they 
  suggest, 
  

   the 
  idea 
  that 
  these 
  hills 
  are 
  what 
  the 
  German 
  geologists 
  catl 
  

   schollengebirge, 
  1 
  that 
  is 
  mountains 
  which 
  have 
  originated 
  from 
  

   straight 
  up 
  and 
  down 
  thrusts, 
  instead 
  of 
  from 
  lateral 
  compression, 
  like 
  

   the 
  Alps 
  and 
  Himalayas. 
  If 
  this 
  is 
  so, 
  the 
  faults 
  by 
  which 
  the 
  fault 
  

   scarps 
  are 
  formed 
  would 
  be 
  normal 
  faults, 
  and 
  so 
  far 
  from 
  there 
  

   having 
  been 
  any 
  compression, 
  the 
  elevation 
  of 
  these 
  hills 
  would 
  have 
  

   been 
  accompanied 
  by 
  an 
  extension 
  of 
  the 
  surface. 
  The 
  state 
  of 
  

   strain 
  too, 
  which 
  preceded 
  the 
  earthquake 
  would 
  have 
  been 
  one 
  of 
  

   tension 
  and 
  not 
  compression. 
  

  

  The 
  mechanism 
  of 
  the 
  production 
  of 
  this 
  form 
  of 
  mountain 
  is 
  not 
  

   properly 
  understood, 
  and 
  a 
  condition 
  of 
  tensile 
  strain 
  in 
  the 
  crust 
  of 
  

   the 
  earth 
  would 
  be 
  still 
  more 
  difficult 
  to 
  explain, 
  but 
  the 
  fact 
  of 
  the 
  

   existence 
  of 
  such 
  mountains 
  and 
  structure 
  cannot 
  be 
  gainsaid, 
  so 
  the 
  

   possibility 
  of 
  the 
  state 
  of 
  tensile 
  strain 
  they 
  imply 
  must 
  be 
  allowed. 
  

  

  If 
  such 
  is 
  the 
  nature 
  of 
  the 
  Assam 
  range, 
  and 
  of 
  the 
  cause 
  of 
  this 
  

  

  ' 
  There 
  is 
  no 
  English 
  equivalent 
  of 
  the 
  word 
  'scholle' 
  as 
  used 
  by 
  German 
  geologists. 
  The 
  

   German 
  precedent 
  has 
  been 
  followed 
  by 
  some 
  authors 
  in 
  America 
  and 
  England, 
  and 
  the 
  

   German 
  words 
  rendered 
  as 
  * 
  block 
  ' 
  and 
  ' 
  block 
  mountains.' 
  The 
  practice 
  seems 
  inconvenient 
  

   as 
  it 
  might 
  easily 
  happen 
  that 
  the 
  same 
  word, 
  block, 
  was 
  required 
  in 
  its 
  ordinary 
  and 
  its 
  special 
  

   sense 
  in 
  the 
  course 
  ot 
  the 
  same 
  sentence. 
  This 
  would 
  lead 
  to 
  confusion, 
  and 
  I 
  suggest 
  the 
  

   word 
  plax, 
  from 
  the 
  Greek 
  word 
  for 
  a 
  block 
  of 
  stone, 
  as 
  a 
  satisfactory 
  equivalent 
  for 
  the 
  word 
  

   * 
  Scholle 
  ' 
  or 
  ' 
  block,' 
  in 
  its 
  special 
  sense. 
  

  

  ( 
  167 
  ) 
  

  

  