﻿W. 
  G. 
  Foye 
  — 
  Geoloyy 
  of 
  the 
  Lau 
  Islands. 
  349 
  

  

  In 
  this 
  connection 
  it 
  is 
  important 
  to 
  note 
  that 
  the 
  Lakemba 
  

   lagoon 
  has 
  a 
  maximum 
  depth 
  of 
  14 
  fathoms, 
  the 
  Aiwa 
  lagoon 
  

   slightly 
  to 
  the 
  southeast, 
  21 
  fathoms, 
  and 
  the 
  lagoons 
  of 
  the 
  

   Argo 
  reefs, 
  15 
  miles 
  to 
  the 
  east, 
  have 
  a 
  depth 
  on 
  the 
  western 
  

   side 
  of 
  20 
  fathoms, 
  on 
  the 
  eastern 
  side 
  of 
  35 
  fathoms. 
  These 
  

   lagoon 
  depths 
  are 
  much 
  greater 
  than 
  the 
  average 
  for 
  the 
  Lau 
  

   Islands 
  and 
  may 
  possibly 
  be 
  attributed 
  to 
  the 
  eastern 
  tilting 
  

   movement 
  described 
  above. 
  

  

  Application 
  of 
  the 
  Results 
  of 
  the 
  Expedition 
  to 
  Coral 
  

  

  Reef 
  Theories. 
  

  

  From 
  the 
  facts 
  just 
  stated 
  it 
  is 
  apparent 
  that 
  the 
  elevated 
  

   limestones 
  of 
  the 
  Lau 
  Islands 
  were 
  deposited 
  on 
  an 
  eroded 
  sur- 
  

   face 
  of 
  volcanic 
  rocks 
  which 
  subsided 
  in 
  accordance 
  with 
  the 
  

   principles 
  of 
  Darwin's 
  theory. 
  It 
  has 
  been 
  questioned 
  whether 
  

   this 
  process 
  explains 
  the 
  development 
  of 
  modern 
  atolls. 
  Alex- 
  

   ander 
  Agassiz 
  inferred 
  that 
  coral 
  banks 
  similar 
  to 
  the 
  Florida 
  

   banks 
  were 
  the 
  result. 
  Likewise 
  Daly 
  considers 
  atolls 
  as 
  

   special, 
  post-Pleistocene, 
  forms 
  of 
  coral 
  reefs. 
  

  

  According 
  to 
  Daly, 
  Kambara 
  is 
  an 
  atoll 
  which 
  developed 
  on 
  

   a 
  platform 
  carved 
  on 
  Tertiary 
  limestones, 
  during 
  the 
  Pleistocene, 
  

   and 
  which 
  has 
  since 
  been 
  elevated. 
  The 
  coraliferous 
  lime- 
  

   stones 
  of 
  the 
  island 
  now 
  stand 
  at 
  an 
  elevation 
  of 
  400 
  feet, 
  or 
  

   more, 
  above 
  the 
  sea. 
  Since 
  the 
  rise 
  of 
  the 
  waters 
  after 
  the 
  

   Glacial 
  period, 
  as 
  stated 
  by 
  this 
  writer, 
  was 
  between 
  250 
  and 
  

   300 
  feet, 
  it 
  would 
  seem 
  that 
  there 
  should 
  be 
  evidence 
  of 
  an 
  

   unconformity 
  between 
  the 
  Tertiary 
  platform 
  and 
  the 
  post- 
  

   Pleistocene 
  reef 
  exposed 
  in 
  the 
  sea-cliffs 
  ; 
  no 
  evidence 
  of 
  such 
  

   an 
  unconformity 
  was 
  seen 
  either 
  in 
  Kambara 
  or 
  any 
  similar 
  

   island, 
  although 
  the 
  cliffs 
  have 
  been 
  cut 
  back 
  sufficiently 
  to 
  

   expose 
  such 
  unconformities 
  if 
  they 
  were 
  present. 
  

  

  That 
  the 
  uplift 
  of 
  the 
  limestone 
  islands 
  is 
  comparatively 
  

   recent 
  in 
  date 
  is 
  apparent 
  from 
  the 
  fact 
  that 
  the 
  included 
  corals 
  

   are 
  Pleistocene 
  or 
  Recent. 
  Their 
  age 
  was 
  kindly 
  determined 
  

   for 
  the 
  writer 
  by 
  Dr. 
  T. 
  W. 
  Vaughan. 
  Assuming 
  that 
  Fulanga 
  

   owes 
  its 
  atoll 
  form 
  to 
  post-Pleistocene 
  growth 
  on 
  a 
  Pleistocene, 
  

   wave- 
  cut 
  platform, 
  this 
  platform 
  should 
  now 
  stand 
  near 
  the 
  

   present 
  sea-level, 
  as 
  the 
  summit 
  of 
  the 
  uplifted 
  atoll-rim 
  is 
  240 
  

   feet 
  above 
  that 
  level. 
  It 
  is 
  apparent, 
  therefore, 
  that 
  the 
  present 
  

   level 
  lagoon, 
  which 
  is 
  from 
  10 
  to 
  12 
  fathoms 
  in 
  depth, 
  cannot 
  

   be 
  ascribed 
  to 
  Pleistocene 
  wave-cutting. 
  Hence 
  it 
  is 
  inferred 
  

   that 
  atolls 
  developed 
  as 
  a 
  result 
  of 
  the 
  subsidence 
  of 
  the 
  

   Tertiarv 
  volcanoes. 
  

  

  t/ 
  

  

  The 
  limestone 
  rim 
  of 
  Lakemba 
  has 
  the 
  appearance 
  of 
  a 
  

   barrier-reef 
  formed 
  during 
  subsidence. 
  The 
  exact 
  location 
  of 
  

   the 
  reef-edge 
  is 
  not 
  known, 
  for 
  it 
  is 
  almost 
  impossible 
  to 
  recog- 
  

   nize 
  ancient 
  reef-edges 
  in 
  masses 
  of 
  elevated 
  limestone. 
  If 
  the 
  

  

  