﻿A. 
  Agassis 
  — 
  Explorations 
  of 
  the 
  " 
  AlbatrossP 
  371 
  

  

  due 
  to 
  the 
  difference 
  in 
  the 
  height 
  of 
  the 
  tides, 
  which 
  is 
  very 
  

   small 
  in 
  the 
  Paumotus, 
  while 
  in 
  these 
  groups 
  it 
  may 
  be 
  five 
  

   and 
  even 
  six 
  feet. 
  

  

  From 
  Jaluit 
  we 
  visited 
  among 
  the 
  Carolines, 
  the 
  islands 
  and 
  

   atolls 
  of 
  Kusaie, 
  Pingelap, 
  Ponapi, 
  Andema, 
  Losap, 
  Namu, 
  

   the 
  Royalist 
  Group, 
  Truk 
  and 
  Namonuito, 
  obtaining 
  thus 
  an 
  

   excellent 
  idea 
  of 
  the 
  character 
  of 
  the 
  high 
  volcanic 
  islands 
  of 
  

   the 
  group 
  from 
  our 
  examinations 
  of 
  Kusaie 
  and 
  of 
  Ponapi, 
  

   while 
  the 
  others 
  represent 
  the 
  conditions 
  of 
  the 
  low 
  atolls, 
  

   having 
  probably 
  a 
  volcanic 
  basis, 
  but 
  this 
  was 
  not 
  observed 
  at 
  

   any 
  of 
  those 
  we 
  examined. 
  

  

  The 
  reefs 
  of 
  the 
  volcanic 
  islands 
  of 
  the 
  Carolines 
  are 
  similar 
  

   in 
  character 
  to 
  those 
  of 
  the 
  Society 
  Islands, 
  though 
  there 
  are 
  

   some 
  features, 
  such 
  as 
  the 
  great 
  width 
  of 
  the 
  platforms 
  of 
  sub- 
  

   marine 
  erosion 
  of 
  Ponapi 
  and 
  of 
  Kusaie, 
  and 
  the 
  development 
  

   of 
  a 
  border 
  of 
  mangrove 
  islands 
  at 
  the 
  base 
  of 
  the 
  volcanic 
  

   islands, 
  which 
  are 
  not 
  found 
  in 
  the 
  Society 
  Islands. 
  

  

  The 
  Truk 
  Archipelago 
  was 
  perhaps 
  the 
  most 
  interesting 
  of 
  

   the 
  island 
  groups 
  of 
  the 
  Carolines, 
  and 
  it 
  is 
  the 
  only 
  group 
  of 
  

   volcanic 
  islands 
  surrounded 
  by 
  an 
  encircling 
  reef 
  which 
  I 
  have 
  

   thus 
  far 
  seen 
  in 
  the 
  Pacific 
  which 
  at 
  first 
  glance 
  lends 
  any 
  

   support 
  to 
  the 
  theory 
  of 
  the 
  formation 
  of 
  such 
  island-groups 
  

   as 
  Truk 
  by 
  subsidence. 
  This 
  group 
  was 
  not 
  visited 
  by 
  either 
  

   Darwin 
  or 
  Dana 
  ; 
  and 
  I 
  can 
  well 
  imagine 
  that 
  an 
  investigator 
  

   seeing 
  this 
  group 
  among 
  the 
  first 
  coral 
  reefs 
  would 
  readily 
  

   describe 
  the 
  islands 
  as 
  the 
  summits, 
  nearly 
  denuded, 
  of 
  a 
  

   great 
  island 
  which 
  had 
  gradually 
  sunk, 
  But 
  a 
  closer 
  examina- 
  

   tion 
  will 
  readily 
  show, 
  1 
  think, 
  that 
  this 
  group 
  is 
  not 
  an 
  excep- 
  

   tion 
  to 
  the 
  general 
  rule 
  thus 
  far 
  obtaining 
  in 
  all 
  the 
  island 
  groups 
  

   of 
  the 
  Pacific 
  I 
  have 
  visited 
  during 
  this 
  trip; 
  that 
  we 
  must 
  

   look 
  to 
  submarine 
  erosion 
  and 
  to 
  a 
  multitude 
  of 
  local 
  mechani- 
  

   cal 
  causes 
  for 
  our 
  explanation 
  of 
  the 
  formation 
  of 
  atolls 
  and 
  of 
  

   barrier 
  and 
  encircling 
  reefs, 
  and 
  that, 
  on 
  the 
  contrary, 
  subsi- 
  

   dence 
  has 
  played 
  no 
  part 
  in 
  bringing 
  about 
  existing 
  conditions 
  

   of 
  the 
  atolls 
  of 
  the 
  South 
  and 
  Central 
  Pacific. 
  

  

  Xowhere 
  have 
  we 
  seen 
  better 
  exemplified 
  than 
  at 
  Truk 
  how 
  

   important 
  a 
  part 
  is 
  played 
  by 
  the 
  existence 
  of 
  a 
  submarine 
  

   platform 
  in 
  the 
  growth 
  of 
  coral 
  reefs. 
  The 
  encircling 
  reef 
  

   protects 
  the 
  many 
  islands 
  of 
  the 
  group 
  against 
  a 
  too 
  rapid 
  

   erosion, 
  so 
  that 
  they 
  are 
  edged 
  by 
  narrow 
  fringing 
  reefs, 
  and 
  

   nowhere 
  do 
  we 
  find 
  the 
  wide 
  platforms 
  so 
  essential 
  to 
  the 
  for- 
  

   mation 
  of 
  barrier 
  reefs. 
  The 
  effect 
  of 
  the 
  northeast 
  trades 
  

   blowing 
  so 
  constantly 
  in 
  one 
  direction 
  for 
  the 
  greater 
  part 
  of 
  

   the 
  year 
  is 
  of 
  course 
  very 
  great 
  ; 
  the 
  disintegration 
  and 
  erosion 
  

   of 
  islands 
  within 
  its 
  influence 
  is 
  incessant, 
  and 
  their 
  action 
  

   undoubtedly 
  one 
  of 
  the 
  essential 
  factors 
  in 
  shaping 
  the 
  atolls 
  

   of 
  the 
  different 
  groups, 
  not 
  only 
  according 
  to 
  the 
  local 
  posi- 
  

  

  