﻿A. 
  Agassis 
  — 
  Explorations 
  of 
  the 
  " 
  Albatross.'' 
  195 
  

  

  Bora-Bora 
  arid 
  Maupiti, 
  rise 
  in 
  slopes 
  and 
  nearly 
  vertical 
  walls, 
  

   the 
  former 
  to 
  a 
  height 
  of 
  nearly 
  2100 
  feet, 
  the 
  other 
  to 
  about 
  

   1100 
  feet. 
  

  

  The 
  only 
  island 
  of 
  the 
  Cook 
  Group 
  which 
  we 
  examined 
  was 
  

   Aitutaki, 
  as 
  Atiu 
  is 
  composed 
  of 
  elevated 
  limestone, 
  and 
  Karo- 
  

   tonga 
  is 
  volcanic 
  ; 
  I 
  hoped 
  we 
  might 
  find 
  that 
  atoll 
  to 
  be 
  in 
  

   part 
  volcanic 
  and 
  in 
  part 
  composed 
  of 
  elevated 
  coralliferous 
  

   limestone 
  : 
  we 
  found 
  it 
  to 
  be 
  volcanic, 
  an 
  island 
  with 
  the 
  

   structure 
  of 
  Bora-Bora 
  on 
  a 
  smaller 
  scale. 
  

  

  AVe 
  anchored 
  at 
  .Xiue, 
  an 
  island 
  composed 
  of 
  elevated 
  coral- 
  

   liferous 
  limestone 
  showing 
  three 
  well-marked 
  terraces, 
  the 
  

   lowest 
  of 
  not 
  more 
  than 
  5 
  to 
  10 
  feet 
  and 
  in 
  many 
  places 
  disap- 
  

   pearing 
  completely, 
  the 
  limestone 
  cliffs 
  rising 
  vertically 
  from 
  

   the 
  sea 
  well 
  into 
  the 
  second 
  or 
  even 
  the 
  third 
  terraces. 
  The 
  

   vertical 
  faces 
  of 
  the 
  cliffs 
  are 
  dotted 
  with 
  caverns 
  and 
  deeply 
  

   indented 
  by 
  small 
  calions 
  extending 
  at 
  right 
  angles 
  to 
  the 
  face 
  

   of 
  the 
  shore 
  or 
  forming 
  blunt 
  headlands 
  separating 
  short 
  

   reaches 
  of 
  coral 
  sand 
  beaches. 
  

  

  The 
  second 
  terrace 
  varies 
  in 
  height 
  from 
  50 
  to 
  60 
  feet, 
  the 
  

   third 
  from 
  90 
  to 
  100 
  feet. 
  The 
  second 
  terrace 
  is 
  deeply 
  under- 
  

   cut 
  ; 
  and 
  in 
  the 
  higher 
  vertical 
  cliffs 
  extending 
  into 
  the 
  third 
  

   terrace 
  from 
  the 
  sea, 
  the 
  former 
  positions 
  of 
  the 
  terraces 
  are 
  

   usually 
  indicated 
  by 
  lines 
  of 
  caverns. 
  There 
  are 
  corals 
  on 
  

   the 
  sea 
  slopes 
  of 
  the 
  first 
  terrace, 
  extending 
  to 
  10 
  or 
  12 
  

   fathoms, 
  growing 
  much 
  as 
  they 
  are 
  found 
  at 
  Makatea. 
  

  

  From 
  Xiue 
  we 
  went 
  to 
  the 
  Tongas, 
  which 
  we 
  found 
  a 
  most 
  

   interesting 
  group. 
  The 
  elevated 
  Tertiary 
  coralliferous 
  lime- 
  

   stones 
  take 
  here 
  their 
  greatest 
  development, 
  and 
  are 
  on 
  a 
  scale 
  

   far 
  beyond 
  that 
  of 
  their 
  development 
  in 
  the 
  Lau 
  Group 
  of 
  the 
  

   Fijis, 
  or 
  the 
  Paumotus. 
  The 
  first 
  island 
  of 
  the 
  Tongas 
  we 
  

   visited, 
  Eua, 
  is 
  perhaps 
  the 
  most 
  interesting 
  of 
  the 
  islands, 
  

   composed 
  of 
  Tertiary 
  elevated 
  coralliferous 
  limestone 
  I 
  have 
  

   visited. 
  From 
  Dana 
  ? 
  s 
  account 
  of 
  it, 
  evidently 
  given 
  at 
  second 
  

   hand, 
  1 
  expected 
  to 
  find 
  an 
  island 
  somewhat 
  like 
  Yiti 
  Levu 
  on 
  

   a 
  very 
  much 
  smaller 
  scale. 
  But 
  as 
  we 
  steamed 
  up 
  to 
  it 
  from 
  

   the 
  east 
  there 
  could 
  be 
  no 
  mistaking 
  the 
  magnificent 
  face 
  of 
  

   nearly 
  vertical 
  limestone 
  cliffs 
  forming 
  the 
  whole 
  eastern 
  face 
  

   of 
  the 
  island, 
  and 
  at 
  points 
  rising 
  to 
  over 
  a 
  thousand 
  feet 
  in 
  

   height. 
  At 
  all 
  projecting 
  points 
  lines 
  of 
  terraces 
  were 
  plainly 
  

   marked 
  : 
  at 
  the 
  northern 
  point 
  three 
  con 
  Id 
  be 
  followed, 
  and 
  at 
  

   the 
  southern 
  extremity 
  five, 
  with 
  traces 
  of 
  a 
  sixth 
  perhaps. 
  

  

  Upon 
  rounding 
  the 
  southern 
  extremity 
  of 
  the 
  island 
  we 
  

   could 
  see 
  that 
  the 
  island 
  was 
  composed 
  of 
  two 
  ridges, 
  running- 
  

   north, 
  separated 
  by 
  a 
  deep 
  valley, 
  the 
  western 
  ridge 
  being 
  

   much 
  lower 
  than 
  the 
  eastern, 
  not 
  rising 
  to 
  a 
  greater 
  height 
  

   than 
  a 
  little 
  over 
  500 
  feet. 
  The 
  western 
  ridge 
  is 
  also 
  composed 
  

   of 
  limestone, 
  and 
  at 
  the 
  headlands 
  we 
  could 
  trace 
  three 
  ter- 
  

  

  