﻿38 
  A. 
  Agassiz 
  — 
  Explorations 
  of 
  the 
  "Albatross" 
  

  

  Paumotu 
  group. 
  Skirting 
  the 
  northern 
  shore 
  from 
  a 
  point 
  a 
  

   little 
  west 
  of 
  Tiputa 
  Pass, 
  we 
  entered 
  the 
  lagoon 
  through 
  

   Avatoru 
  Pass, 
  anchoring 
  off 
  the 
  village. 
  This 
  pass 
  is 
  quite 
  

   narrow, 
  with 
  a 
  strong 
  current 
  running 
  out 
  the 
  greater 
  part 
  of 
  

   the 
  time, 
  especially 
  in 
  easterly 
  winds. 
  It 
  varies 
  in 
  depth 
  

   between 
  9 
  and 
  10 
  fathoms, 
  shoaling 
  near 
  the 
  inner 
  entrance 
  to 
  

   about 
  3^- 
  fathoms, 
  and 
  deepening 
  again 
  to 
  6 
  or 
  7 
  fathoms, 
  

   and 
  gradually 
  passing 
  into 
  15 
  to 
  17 
  fathoms, 
  which 
  is 
  the 
  

   average 
  depth 
  of 
  the 
  lagoon 
  from 
  Avatoru 
  Pass 
  to 
  the 
  south 
  

   or 
  weather 
  shore, 
  a 
  distance 
  of 
  about 
  13 
  miles. 
  

  

  We 
  made 
  an 
  examination 
  of 
  the 
  northern 
  side 
  of 
  the 
  lagoon 
  

   between 
  Avatoru 
  and 
  Tiputa 
  Passes. 
  The 
  lagoon 
  beach 
  of 
  the 
  

   northern 
  shore 
  is 
  quite 
  steep, 
  and 
  is 
  composed 
  of 
  moderately 
  

   coarse 
  broken 
  coral 
  sand 
  at 
  the 
  base, 
  and 
  of 
  larger 
  fragments 
  

   of 
  corals 
  along 
  the 
  upper 
  face, 
  which 
  is 
  about 
  5 
  to 
  6 
  feet 
  above 
  

   high- 
  water 
  mark. 
  These 
  coral 
  fragments 
  are 
  derived 
  in 
  part 
  

   from 
  the 
  corals 
  living 
  on 
  the 
  lagoon 
  face 
  of 
  the 
  northern 
  shore, 
  

   and 
  in 
  part 
  of 
  fragments 
  broken 
  by 
  the 
  waves 
  from 
  somewhat 
  

   below 
  the 
  low-water 
  mark. 
  The 
  ledge 
  which 
  underlies 
  the 
  

   beach 
  crops 
  out 
  at 
  many 
  places 
  on 
  the 
  lagoon 
  side 
  of 
  the 
  

   northern 
  shore 
  ; 
  we 
  traced 
  it 
  also 
  along 
  the 
  shores 
  of 
  Avatoru 
  

   Pass, 
  and 
  about 
  half 
  way 
  across 
  the 
  narrow 
  land 
  running 
  

   between 
  Avatoru 
  and 
  Tiputa 
  Passes. 
  It 
  crops 
  out 
  also 
  at 
  

   various 
  points 
  between 
  them 
  in 
  the 
  narrow 
  cuts 
  which 
  divide 
  

   this 
  part 
  of 
  the 
  northern 
  land 
  of 
  the 
  lagoon 
  into 
  a 
  number 
  of 
  

   smaller 
  islands. 
  These 
  secondary 
  passes 
  leave 
  exposed 
  the 
  

   underlying 
  ledge, 
  full 
  of 
  fossil 
  corals. 
  In 
  some 
  cases 
  there 
  is 
  

   left 
  a 
  clear 
  channel 
  extending 
  across 
  from 
  the 
  lagoon 
  to 
  the 
  

   northern 
  side 
  through 
  which 
  water 
  flows 
  at 
  high 
  or 
  half 
  tide. 
  

   In 
  other 
  cases 
  the 
  cuts 
  are 
  silted 
  up 
  with 
  coral 
  sand 
  blown 
  in 
  

   from 
  the 
  lagoon 
  side. 
  In 
  others, 
  the 
  cut 
  is 
  shut 
  off 
  by 
  a 
  high 
  

   sand-bank, 
  or 
  a 
  bank 
  composed 
  of 
  broken 
  fragments 
  of 
  corals, 
  

   leaving 
  access 
  to 
  the 
  water 
  from 
  the 
  northern 
  shore 
  only 
  ; 
  and 
  

   finally 
  the 
  cuts 
  are 
  also 
  shut 
  off 
  on 
  the 
  northern 
  side 
  by 
  sand 
  

   and 
  broken 
  coral 
  banks, 
  the 
  extension 
  of 
  the 
  north-shore 
  beach 
  

   leaving 
  a 
  depression 
  which 
  at 
  first 
  is 
  filled 
  with 
  salt-water 
  and 
  

   gradually 
  silted 
  up 
  both 
  from 
  the 
  lagoon 
  side 
  and 
  the 
  sea 
  side, 
  

   and 
  forms 
  the 
  typical 
  north-shore 
  land 
  of 
  the 
  lagoon. 
  This 
  

   building 
  up 
  of 
  the 
  land 
  of 
  the 
  Paumotu 
  atolls 
  simultaneously 
  

   both 
  by 
  the 
  accumulation 
  of 
  sand 
  from 
  the 
  lagoon 
  side 
  and 
  the 
  

   sea 
  face, 
  is 
  very 
  characteristic 
  of 
  the 
  atolls 
  of 
  that 
  group. 
  It 
  is 
  

   a 
  feature 
  which 
  I 
  have 
  not 
  seen 
  so 
  marked 
  in 
  any 
  other 
  coral 
  

   reef 
  district. 
  

  

  On 
  the 
  lagoon 
  side 
  the 
  slope 
  from 
  the 
  beach 
  is 
  very 
  gradual 
  

   into 
  16 
  and 
  17 
  fathoms, 
  and 
  corals 
  appear 
  to 
  flourish 
  on 
  the 
  

   lagoon 
  slope 
  to 
  6 
  or 
  8 
  fathoms 
  only, 
  in 
  some 
  cases 
  consisting 
  of 
  

   Madrepores, 
  Porites, 
  Astrseans. 
  and 
  Pocillopores. 
  The 
  corals 
  

  

  