﻿194 
  A. 
  Agassis 
  — 
  Explorations 
  of 
  the 
  "Albatross" 
  

  

  Marambo, 
  600 
  fathoms 
  ; 
  between 
  it 
  and 
  Kambara, 
  450 
  fathoms 
  ; 
  

   and 
  finally, 
  about 
  15 
  miles 
  west 
  of 
  Kambara, 
  we 
  sounded 
  in 
  

   990 
  fathoms. 
  These 
  soundings 
  would 
  indicate 
  a 
  continuous 
  

   plateau 
  of 
  moderate 
  depths 
  from 
  Wailangolala 
  south 
  upon 
  

   which 
  the 
  islands 
  of 
  the 
  Lau 
  Group 
  rise. 
  

  

  On 
  our 
  way 
  back 
  to 
  Papeete 
  from 
  the 
  Paumotus 
  we 
  exam- 
  

   ined 
  the 
  eastern 
  coast 
  of 
  Tahiti, 
  and 
  from 
  Papeete 
  examined 
  

   the 
  western 
  coast 
  as 
  far 
  as 
  Port 
  Phaeton, 
  at 
  Tararoa 
  Isthmus. 
  

   We 
  examined, 
  in 
  a 
  general 
  way, 
  the 
  Leeward 
  Society 
  Islands 
  : 
  

   Murea, 
  Huaheine, 
  Paiatea, 
  Tahaa, 
  Bora-Bora, 
  Motu 
  Iti, 
  and 
  

   Maupiti. 
  There 
  .are 
  excellent 
  charts 
  of 
  the 
  Society 
  Islands, 
  so 
  

   that 
  it 
  was 
  comparatively 
  simple 
  to 
  examine 
  the 
  typical 
  points 
  

   of 
  the 
  group 
  and 
  to 
  gain 
  an 
  idea 
  of 
  their 
  structure 
  as 
  far 
  as 
  it 
  

   relates 
  to 
  coral 
  reefs. 
  The 
  Society 
  Islands 
  are 
  all 
  volcanic 
  

   islands 
  edged 
  with 
  shore 
  platforms, 
  some 
  of 
  great 
  width, 
  upon 
  

   which 
  the 
  barrier 
  or 
  the 
  fringing 
  reefs 
  of 
  the 
  islands 
  have 
  

   grown. 
  The 
  structure 
  of 
  the 
  reefs 
  of 
  the 
  Society 
  Islands 
  is 
  

   very 
  similar 
  to 
  that 
  of 
  the 
  Fiji 
  reefs 
  round 
  volcanic 
  islands. 
  

   A 
  comparison, 
  for 
  instance, 
  of 
  the 
  charts 
  of 
  Kandavu, 
  Yiti 
  

   Levu, 
  Mbengha, 
  Nairai, 
  and 
  of 
  other 
  volcanic 
  islands 
  in 
  the 
  

   Fijis, 
  with 
  those 
  of 
  the 
  Society 
  Group, 
  will 
  at 
  once 
  show 
  their 
  

   identity. 
  Huge 
  platforms 
  of 
  submarine 
  denudation 
  and 
  ero- 
  

   sion 
  characterize 
  both, 
  with 
  fringing 
  and 
  barrier 
  reefs 
  deter- 
  

   mined 
  by 
  local 
  conditions. 
  Perhaps 
  it 
  is 
  easier 
  to 
  follow 
  the 
  

   changes 
  which 
  have 
  taken 
  place 
  in 
  the 
  Society 
  Islands 
  ; 
  and 
  

   such 
  islands 
  as 
  Tahaa 
  and 
  Bora-Bora, 
  where 
  we 
  anchored, 
  as 
  

   well 
  as 
  Maupiti, 
  are 
  admirable 
  examples 
  and 
  epitomes 
  of 
  the 
  

   structure 
  and 
  mode 
  of 
  formation 
  of 
  the 
  coral 
  reefs 
  of 
  that 
  

   group. 
  

  

  In 
  Motu 
  Iti 
  and 
  Tetuora 
  the 
  volcanic 
  peaks 
  have 
  disappeared 
  

   leaving 
  nothing 
  but 
  a 
  shallow 
  platform, 
  upon 
  the 
  outer 
  edges 
  

   of 
  which 
  sandy 
  coral 
  islets 
  have 
  been 
  thrown 
  up. 
  There 
  is, 
  

   however, 
  one 
  point 
  in 
  which 
  the 
  barrier 
  reefs 
  of 
  the 
  Society 
  

   Islands 
  differ 
  from 
  those 
  of 
  Fiji. 
  The 
  barrier 
  reefs 
  in 
  Fiji 
  are 
  

   generally 
  indicated 
  merely 
  by 
  reef 
  flats, 
  upon 
  which 
  the 
  sea 
  

   breaks, 
  and 
  an 
  occasional 
  rocky 
  islet 
  or 
  negro-head 
  ; 
  only 
  rarely 
  

   do 
  we 
  find 
  sand 
  keys 
  upon 
  the 
  fringing 
  reefs 
  of 
  the 
  islands 
  of 
  

   Fiji. 
  In 
  the 
  Society 
  Islands, 
  on 
  the 
  contrary, 
  we 
  find 
  the 
  line 
  

   of 
  the 
  barrier 
  reef 
  usually 
  well 
  indicated 
  by 
  long 
  lines 
  of 
  nar- 
  

   row 
  islets 
  thrown 
  upon 
  the 
  reef 
  platforms, 
  exactly 
  as 
  they 
  are 
  

   in 
  the 
  Paumotus. 
  These 
  islands 
  and 
  islets 
  are 
  usually 
  well 
  

   wooded, 
  and 
  thus 
  give 
  a 
  very 
  peculiar 
  aspect 
  to 
  the 
  barrier 
  

   reef. 
  In 
  the 
  case 
  of 
  Bora-Bora, 
  Maupiti, 
  and 
  Aitutaki, 
  for 
  

   instance, 
  we 
  have 
  a 
  central 
  volcanic 
  peak 
  of 
  considerable 
  

   height 
  surrounded 
  by 
  a 
  wide 
  lagoon, 
  the 
  sea 
  edge 
  of 
  which 
  is 
  

   formed 
  by 
  a 
  fringe 
  of 
  wooded 
  islets 
  and 
  islands 
  forming 
  a 
  

   more 
  than 
  half-closed 
  ring 
  around 
  the 
  central 
  island, 
  which, 
  in 
  

  

  