﻿A.Agassis 
  — 
  Explorations 
  of 
  the 
  "Albatross." 
  197 
  

  

  In 
  a 
  distance 
  of 
  nearly 
  10 
  miles 
  northward 
  of 
  £uiku-Alofa 
  the 
  

   plateau 
  is 
  nowhere 
  more 
  than 
  15 
  fathoms 
  deep 
  ; 
  and 
  a 
  long 
  

   tongue 
  runs 
  northward, 
  gradually 
  deepening 
  into 
  20 
  to 
  50 
  

   fathoms 
  to 
  the 
  100 
  fathom 
  line. 
  

  

  The 
  Tonga-Tabu 
  plateau 
  is 
  separated 
  from 
  the 
  Namuka 
  

   Group 
  plateau 
  by 
  a 
  funnel-shaped 
  channel 
  with 
  a 
  depth 
  pass- 
  

   ing 
  rapidly 
  into 
  300 
  fathoms 
  from 
  the 
  100-fathom 
  line. 
  The 
  

   ]S~amuka 
  plateau 
  is 
  rectangular. 
  The 
  principal 
  island 
  is 
  JSTa- 
  

   muka, 
  where 
  we 
  anchored. 
  We 
  found 
  the 
  island 
  to 
  be 
  com- 
  

   posed 
  of 
  Tertiary 
  elevated 
  coralliferous 
  limestone, 
  with 
  a 
  

   shallow 
  sink, 
  filled 
  with 
  brackish 
  water, 
  occupying 
  the 
  south- 
  

   eastern 
  part 
  of 
  the 
  island. 
  The 
  sink 
  is 
  separated 
  by 
  a 
  high 
  

   sand 
  beach, 
  about 
  200 
  yards 
  wide, 
  from 
  the 
  sea. 
  

  

  Namuka 
  Iki, 
  the 
  island 
  next 
  to 
  Namuka, 
  we 
  found 
  to 
  con- 
  

   sist, 
  at 
  its 
  southern 
  extremity, 
  of 
  stratified 
  volcanic 
  material, 
  

   resembling 
  somewhat 
  the 
  so-called 
  soapstone 
  of 
  Fiji. 
  I 
  was 
  

   told 
  that 
  other 
  islands 
  in 
  this 
  group, 
  near 
  Tonumeia, 
  in 
  the 
  

   center 
  of 
  the 
  Namuka 
  plateau, 
  were 
  volcanic. 
  Mango, 
  as 
  we 
  

   could 
  see 
  it 
  from 
  our 
  anchorage, 
  appeared 
  to 
  be 
  volcanic. 
  So 
  

   that 
  this 
  part 
  of 
  the 
  Tongas 
  is, 
  like 
  the 
  Lau 
  Group 
  in 
  Fiji, 
  

   made 
  up 
  of 
  islands 
  in 
  part 
  volcanic 
  and 
  in 
  part 
  composed 
  of 
  

   elevated 
  coralliferous 
  limestone. 
  The 
  eastern 
  edge 
  of 
  the 
  

   Xamuka 
  plateau 
  (which 
  we 
  did 
  not 
  visit) 
  is 
  edged 
  with 
  small 
  

   low 
  islands. 
  We 
  merely 
  steamed 
  by 
  the 
  western 
  islands 
  of 
  the 
  

   Haapai 
  Group, 
  but 
  close 
  enough 
  to 
  see 
  that 
  Tongua, 
  Kotu, 
  and 
  

   Fotuhaa, 
  which 
  are 
  respectively 
  120, 
  120, 
  and 
  200 
  feet 
  high, 
  

   are 
  composed 
  of 
  elevated 
  limestone. 
  The 
  eastern 
  flank 
  of 
  the 
  

   Haapai 
  plateau 
  is 
  edged 
  with 
  long, 
  low 
  islands, 
  with 
  extensive 
  

   coral 
  reefs 
  along 
  the 
  reef 
  flats 
  of 
  these 
  islands. 
  

  

  The 
  Haapai 
  plateau 
  is 
  triangular, 
  with 
  isolated 
  islands 
  rising 
  

   on 
  the 
  northwestern 
  side 
  from 
  the 
  deep 
  water 
  separating 
  it 
  

   from 
  the 
  Yavau 
  plateau. 
  It 
  is 
  separated 
  from 
  the 
  Xamuka 
  

   plateau 
  by 
  a 
  narrow 
  channel 
  with 
  over 
  300 
  fathoms 
  of 
  water. 
  

  

  The 
  northernmost 
  plateau 
  of 
  the 
  broad 
  ridge 
  of 
  the 
  Tonga 
  

   Islands 
  is 
  the 
  Yavau 
  plateau. 
  This 
  is 
  elliptical, 
  with 
  a 
  long 
  

   tongue 
  extending 
  on 
  the 
  eastern 
  face 
  of 
  the 
  ridge 
  toward 
  the 
  

   northern 
  point 
  of 
  the 
  Haapai 
  plateau, 
  ending 
  in 
  isolated 
  banks 
  

   (the 
  Disney 
  and 
  Falcon 
  banks), 
  lying 
  to 
  the 
  northward 
  of 
  the 
  

   broad 
  channel, 
  with 
  over 
  100 
  fathoms 
  separating 
  it 
  from 
  the 
  

   Haapai 
  Group. 
  The 
  Yavau 
  Group 
  is 
  by 
  far 
  the 
  most 
  pictur- 
  

   esque 
  of 
  the 
  Tonga 
  Islands. 
  It 
  consists 
  of 
  the 
  principal 
  island 
  

   of 
  Yavau, 
  extending 
  across 
  the 
  northern 
  part 
  of 
  the 
  Yavau 
  

   plateau. 
  Several 
  parts 
  of 
  the 
  island 
  of 
  Yavau, 
  as 
  at 
  the 
  

   entrance 
  to 
  the 
  harbor 
  of 
  ^seiafu, 
  and 
  at 
  Xeiafu, 
  are 
  finely 
  

   terraced 
  ; 
  four 
  terraces 
  are 
  indicated 
  there, 
  and 
  other 
  flat-topped 
  

   smaller 
  islands 
  show 
  traces 
  of 
  two 
  or 
  three 
  terraces. 
  The 
  

   northern 
  edo-e 
  of 
  Yavau 
  Island 
  rises 
  to 
  a 
  height 
  of 
  more 
  than 
  

  

  