﻿A. 
  Agassis 
  — 
  Explorations 
  of 
  the 
  u 
  Albatross 
  ." 
  41 
  

  

  The 
  slope 
  of 
  the 
  sea 
  face 
  of 
  the 
  elevated 
  ledge 
  was 
  quite 
  

   steep 
  and 
  similar 
  to 
  the 
  lagoon 
  slope, 
  and 
  its 
  upper 
  surface 
  

   weathered 
  by 
  atmospheric 
  and 
  aqueous 
  agencies 
  into 
  all 
  possi- 
  

   ble 
  shapes 
  such 
  as 
  I 
  have 
  mentioned. 
  The 
  slope 
  passed 
  into 
  

   the 
  shore 
  platform, 
  which 
  was 
  shaved 
  down 
  as 
  it 
  were 
  to 
  a 
  gen- 
  

   eral 
  level 
  surface. 
  On 
  the 
  outer 
  edge, 
  within 
  the 
  line 
  of 
  the 
  

   breakers, 
  were 
  growing 
  Pocillopores 
  in 
  great 
  abundance. 
  This 
  

   reef 
  flat 
  or 
  shore 
  platform, 
  as 
  well 
  as 
  the 
  reef 
  platform 
  of 
  the 
  

   north 
  shore, 
  was 
  strewn 
  here 
  and 
  there 
  with 
  huge 
  masses 
  of 
  

   the 
  ledge 
  of 
  elevated 
  reef 
  rock 
  torn 
  from 
  its 
  outer 
  shore. 
  

   Similar 
  rocks 
  and 
  bowlders 
  occur 
  on 
  the 
  lagoon 
  side 
  of 
  the 
  

   islands 
  forming 
  the 
  outer 
  lands 
  of 
  Eairoa; 
  they 
  are 
  either 
  torn 
  

   off 
  from 
  the 
  lagoon 
  face 
  of 
  the 
  outcropping 
  ledge, 
  or 
  are 
  parts 
  

   of 
  the 
  ledge 
  which 
  have 
  remained 
  in 
  place 
  and 
  have 
  not 
  been 
  

   planed 
  down 
  to 
  the 
  base 
  level 
  of 
  the 
  reef. 
  

  

  The 
  amount 
  of 
  water 
  which 
  is 
  forced 
  into 
  such 
  a 
  lagoon 
  as 
  

   Rairoa 
  is 
  something 
  colossal, 
  and 
  when 
  we 
  observe 
  that 
  there 
  

   are 
  but 
  a 
  small 
  number 
  of 
  passages 
  through 
  which 
  it 
  can 
  find 
  

   its 
  way 
  out 
  again 
  on 
  the 
  leeward 
  side, 
  it 
  is 
  not 
  surprising 
  

   that 
  we 
  should 
  meet 
  with 
  such 
  powerful 
  currents 
  (7 
  to 
  8 
  

   knots 
  in 
  several 
  cases) 
  sweeping 
  out 
  of 
  the 
  passages 
  on 
  the 
  lee 
  

   sides. 
  

  

  The 
  islands 
  and 
  islets 
  of 
  Rairoa 
  are 
  fairly 
  well 
  covered 
  with 
  

   low 
  trees 
  and 
  shrubs 
  and 
  large 
  groves 
  of 
  palm 
  trees. 
  

  

  The 
  atolls 
  of 
  Tikehau 
  and 
  Mataiwa, 
  which 
  we 
  also 
  examined, 
  

   present 
  no 
  features 
  which 
  we 
  did 
  not 
  meet 
  in 
  Rairoa. 
  The 
  

   iirst-named 
  atoll 
  shows 
  the 
  same 
  method 
  of 
  formation 
  of 
  the 
  

   land 
  by 
  material 
  piled 
  up 
  both 
  from 
  the 
  lagoon 
  side 
  and 
  the 
  

   sea 
  face 
  ; 
  material 
  derived 
  from 
  the 
  disintegration 
  of 
  the 
  under- 
  

   lying 
  Tertiary 
  limestone 
  which 
  crops 
  out 
  here 
  and 
  there 
  along 
  

   the 
  sea 
  face 
  and 
  the 
  inner 
  shores 
  of 
  the 
  lagoon, 
  or 
  forms 
  across 
  

   the 
  S.W. 
  face 
  of 
  the 
  lagoon 
  an 
  irregular 
  disconnected 
  part 
  of 
  

   the 
  ring 
  of 
  islands 
  and 
  islets 
  encircling 
  that 
  end 
  of 
  the 
  lagoon. 
  

   These 
  islets 
  and 
  islands 
  are 
  more 
  or 
  less 
  connected 
  by 
  fragments 
  

   of 
  the 
  elevated 
  limestone 
  ledge, 
  attesting 
  its 
  greater 
  extension 
  

   in 
  past 
  times. 
  The 
  outer 
  rings 
  of 
  both 
  these 
  atolls 
  are 
  covered 
  

   with 
  vegetation. 
  We 
  could 
  see 
  in 
  the 
  lagoons 
  several 
  rocky 
  

   islets, 
  the 
  fragments 
  of 
  the 
  elevated 
  limestone 
  ledge. 
  

  

  Mataiwa 
  is 
  interesting, 
  as 
  its 
  lagoon 
  is 
  quite 
  shallow; 
  it 
  is 
  

   full 
  of 
  rocky 
  islets, 
  remnants 
  of 
  the 
  underlying 
  limestone 
  ledge 
  

   which 
  crops 
  out 
  above 
  the 
  general 
  level, 
  and 
  has 
  a 
  very 
  narrow 
  

   and 
  shallow 
  entrance, 
  passable 
  for 
  boats 
  only. 
  Some 
  of 
  its 
  

   islands 
  are 
  wooded 
  and 
  appear 
  to 
  have 
  been 
  formed 
  by 
  accre- 
  

   tion 
  of 
  sand 
  from 
  the 
  decomposing 
  ledges 
  of 
  the 
  lagoon. 
  

   The 
  outer 
  ring 
  of 
  land 
  appears 
  formed 
  by 
  sand 
  banks 
  driven 
  

   in 
  from 
  the 
  sea 
  face 
  and 
  driven 
  out 
  from 
  the 
  lagoon 
  side 
  by 
  

   the 
  action 
  of 
  the 
  waves. 
  It 
  is 
  evident 
  that 
  such 
  a 
  lagoon 
  as 
  

  

  