﻿196 
  A. 
  Agassiz 
  — 
  Explorations 
  of 
  the 
  "Albatross" 
  

  

  races. 
  There 
  is 
  a 
  narrow 
  shore 
  platform 
  along 
  the 
  western 
  

   face, 
  at 
  many 
  points 
  of 
  which 
  there 
  are 
  blow-holes 
  where 
  the 
  

   sea 
  throws 
  up 
  spray 
  to 
  a 
  considerable 
  height, 
  but 
  these 
  blow- 
  

   holes 
  are 
  best 
  seen 
  off 
  Cook 
  Point, 
  the 
  southern 
  extremity 
  of 
  

   Tonga-Tabu. 
  

  

  As 
  we 
  steamed 
  along 
  the 
  western 
  face 
  of 
  Eua 
  Island 
  we 
  

   could 
  see 
  the 
  ridges 
  of 
  the 
  eastern 
  side 
  rising 
  above 
  the 
  crest 
  

   of 
  the 
  lower 
  ridge, 
  its 
  slopes 
  indicating 
  a 
  valley 
  of 
  considerable 
  

   size. 
  We 
  anchored 
  at 
  English 
  Roads, 
  opposite 
  the 
  outlet 
  of 
  

   the 
  drainage 
  of 
  the 
  interior 
  basin, 
  where 
  a 
  small 
  river 
  has 
  cut 
  

   its 
  way 
  through 
  a 
  depression 
  in 
  the 
  shore 
  terrace. 
  On 
  landing 
  

   we 
  followed 
  the 
  crest 
  of 
  the 
  western 
  ridge 
  for 
  a 
  few 
  miles 
  and 
  

   could 
  see 
  the 
  whole 
  valley 
  forming 
  the 
  basin 
  of 
  the 
  island 
  

   lying 
  between 
  the 
  two 
  ridges, 
  at 
  our 
  feet 
  ; 
  the 
  slopes 
  leading 
  

   to 
  the 
  bottom 
  are 
  quite 
  gentle, 
  and 
  the 
  valley 
  dips 
  very 
  gradu- 
  

   ally 
  northward 
  back 
  of 
  the 
  outlet 
  on 
  the 
  western 
  shore. 
  Noth- 
  

   ing 
  could 
  show 
  more 
  clearly 
  that 
  such 
  an 
  island 
  was 
  not 
  

   an 
  elevated 
  atoll, 
  but 
  a 
  plateau 
  which 
  has 
  been 
  eroded 
  and 
  

   denuded 
  for 
  a 
  long 
  period 
  of 
  time 
  by 
  atmospheric 
  and 
  other 
  

   agencies, 
  and 
  in 
  which 
  a 
  deep 
  basin- 
  shaped 
  valley 
  with 
  gentle 
  

   slopes 
  has 
  been 
  gouged 
  out 
  — 
  a 
  plateau 
  similar 
  to 
  that 
  of 
  Tonga- 
  

   Tabu 
  Island 
  and 
  of 
  Yavau, 
  but 
  of 
  greater 
  height 
  and 
  less 
  

   extent. 
  

  

  To 
  the 
  westward 
  of 
  the 
  Tonga 
  Islands 
  is 
  a 
  line 
  of 
  volcanic 
  

   islands 
  extending 
  nearly 
  200 
  miles, 
  from 
  Honga 
  Hapai 
  to 
  

   Fanualai, 
  some 
  of 
  which 
  have 
  been 
  active 
  very 
  recently. 
  

   Falcon 
  Island 
  disappeared 
  in 
  1898, 
  and 
  Lette 
  is 
  still 
  active. 
  

   This 
  line 
  of 
  volcanoes 
  runs 
  at 
  a 
  distance 
  of 
  from 
  15 
  to 
  20 
  

   miles 
  parallel 
  with 
  the 
  trend 
  of 
  the 
  four 
  irregularly-shaped 
  

   plateaux 
  upon 
  which 
  rise 
  the 
  Tonga 
  Islands. 
  They 
  are 
  the 
  

   summits 
  of 
  a 
  great 
  ridge, 
  over 
  200 
  miles 
  in 
  length, 
  sloping 
  

   very 
  gradually 
  to 
  the 
  westward 
  and 
  being 
  somewhat 
  more 
  

   steep 
  to 
  the 
  eastward, 
  into 
  deep 
  water, 
  towards 
  the 
  smaller 
  

   platforms 
  from 
  which 
  rise 
  the 
  volcanic 
  peaks 
  of 
  the 
  group. 
  

   The 
  plateaux 
  of 
  Tonga-Tabu, 
  N 
  mnka, 
  Haapai, 
  and 
  Yavau, 
  

   are 
  separated 
  by 
  deep 
  valleys 
  connecting 
  the 
  eastern 
  and 
  

   western 
  flanks 
  of 
  the 
  ridge. 
  These 
  four 
  plateaux 
  rise 
  abruptly 
  

   from 
  the 
  100-fathom 
  line. 
  The 
  extremity 
  of 
  the 
  southern 
  one 
  

   is 
  occupied 
  by 
  Tonga-Tabu 
  Island. 
  The 
  land 
  behind 
  the 
  cliffs 
  

   of 
  its 
  southern 
  coast 
  rises 
  to 
  a 
  height 
  of 
  over 
  250 
  feet, 
  and 
  

   slopes 
  northward 
  very 
  gradually 
  to 
  form 
  the 
  low 
  land 
  which 
  

   occupies 
  the 
  northern 
  coast 
  of 
  the 
  island, 
  and 
  is, 
  except 
  at 
  

   Mount 
  Zion 
  and 
  Cook 
  Hill, 
  not 
  more 
  than 
  from 
  10 
  to 
  20 
  feet 
  

   above 
  the 
  level 
  of 
  the 
  sea. 
  At 
  Cook 
  Point 
  and 
  along 
  the 
  

   southern 
  coast 
  three 
  terraces 
  are 
  indicated. 
  The 
  northern 
  

   coast 
  is 
  deeply 
  indented 
  by 
  shallow 
  bays, 
  full 
  of 
  islands, 
  reef 
  

   flats, 
  and 
  reef 
  patches, 
  on 
  which 
  corals 
  grow 
  in 
  great 
  profusion. 
  

  

  