﻿1874.] 
  f 
  Challenger 
  9 
  Soundings 
  in 
  the 
  Southern 
  Sea. 
  45 
  

  

  under 
  a 
  high 
  power, 
  as 
  minute 
  cylinders 
  scattered 
  over 
  the 
  field. 
  The 
  

   larger 
  Foraminifera 
  are 
  attacked, 
  and 
  instead 
  of 
  being 
  vividly 
  white 
  

   and 
  delicately 
  sculptured, 
  they 
  become 
  brown 
  and 
  worn, 
  and 
  finally 
  they 
  

   break 
  up, 
  each 
  according 
  to 
  its 
  fashion 
  ; 
  the 
  chamber-walls 
  of 
  Globigerina 
  

   fall 
  into 
  wedge-shaped 
  pieces 
  which 
  quickly 
  disappear, 
  and 
  a 
  thick 
  rough 
  

   crust 
  breaks 
  away 
  from 
  the 
  surface 
  of 
  Orbulina, 
  leaving 
  a 
  thin 
  inner 
  

   sphere, 
  at 
  first 
  beautifully 
  transparent, 
  but 
  soon 
  becoming 
  opaque 
  and 
  

   crumbling 
  away. 
  

  

  In 
  the 
  mean 
  time, 
  the 
  proportion 
  of 
  the 
  amorphous 
  " 
  red 
  clay" 
  to 
  the 
  

   calcareous 
  elements 
  of 
  all 
  kinds, 
  increases, 
  until 
  the 
  latter 
  disappear, 
  with 
  

   the 
  exception 
  of 
  a 
  few 
  scattered 
  shells 
  of 
  the 
  larger 
  Foraminifera, 
  which 
  

   are 
  still 
  found, 
  even 
  in 
  the 
  most 
  characteristic 
  samples 
  of 
  the 
  " 
  red 
  clay." 
  

  

  There 
  seems 
  to 
  be 
  no 
  room 
  left 
  for 
  doubt 
  that 
  the 
  red 
  clay 
  is 
  essenti- 
  

   ally 
  the 
  insoluble 
  residue, 
  the 
  ash, 
  as 
  it 
  were, 
  of 
  the 
  calcareous 
  organisms 
  

   which 
  form 
  the 
  Globigerina-ooze, 
  after 
  the 
  calcareous 
  matter 
  has 
  been 
  by 
  

   some 
  means 
  removed. 
  An 
  ordinary 
  mixture 
  of 
  calcareous 
  Foraminifera 
  

   with 
  the 
  shells 
  of 
  Pteropods, 
  forming 
  a 
  fair 
  sample 
  of 
  " 
  Globigerina-ooze 
  " 
  

   from 
  near 
  St. 
  Thomas, 
  was 
  carefully 
  washed 
  and 
  subjected 
  by 
  Mr. 
  

   Buchanan 
  to 
  the 
  action 
  of 
  weak 
  acid 
  ; 
  and 
  he 
  found 
  that 
  there 
  remained, 
  

   after 
  the 
  carbonate 
  of 
  lime 
  had 
  been 
  removed, 
  about 
  one 
  per 
  cent, 
  of 
  a 
  

   reddish 
  mud, 
  consisting 
  of 
  silica, 
  alumina, 
  and 
  the 
  red 
  oxide 
  of 
  iron. 
  

   This 
  experiment 
  has 
  been 
  frequently 
  repeated 
  with 
  different 
  samples 
  

   of 
  " 
  Globigerina-ooze," 
  and 
  always 
  with 
  the 
  result 
  that 
  a^mall 
  proportion 
  

   of 
  a 
  red 
  sediment 
  remains, 
  which 
  possesses 
  all 
  the 
  characters 
  of 
  the 
  " 
  red 
  

   clay." 
  

  

  In 
  the 
  Globigerina-ooze, 
  siliceous 
  bodies, 
  including 
  the 
  spicules 
  of 
  

   Sponges, 
  the 
  spicules 
  and 
  tests 
  of 
  Radiolarians,and 
  the 
  frustulesof 
  Diatoms 
  

   occur 
  in 
  appreciable 
  proportion 
  ; 
  and 
  these 
  also 
  diminish 
  in 
  number, 
  and 
  

   the 
  more 
  delicate 
  of 
  them 
  disappear 
  in 
  the 
  transition 
  from 
  the 
  calcareous 
  

   ooze 
  to 
  the 
  " 
  red 
  clay." 
  

  

  I 
  have 
  already 
  alluded 
  to 
  the 
  large 
  quantity 
  of 
  nodules 
  of 
  the 
  peroxide 
  

   of 
  manganese 
  which 
  were 
  brought 
  up 
  by 
  the 
  trawl 
  from 
  the 
  red-clay 
  area 
  

   on 
  the 
  13th 
  of 
  March. 
  Such 
  nodules 
  seem 
  to 
  occur 
  universally 
  in 
  this 
  

   formation. 
  No 
  manganese 
  can 
  be 
  detected 
  in 
  the 
  Globigerina-ooze 
  ; 
  but 
  no 
  

   sooner 
  has 
  the 
  removal 
  of 
  the 
  carbonate 
  of 
  lime 
  commenced 
  than 
  small 
  

   black 
  grains 
  make 
  their 
  appearance, 
  usually 
  rounded 
  and 
  mammillated 
  on 
  

   the 
  surface, 
  miniatures, 
  in 
  fact, 
  of 
  the 
  larger 
  nodules 
  which 
  abound 
  in 
  the 
  

   clay 
  ; 
  and, 
  at 
  the 
  same 
  time, 
  any 
  large 
  organic 
  body, 
  such 
  as 
  a 
  shark's 
  tooth, 
  

   that 
  may 
  happen 
  to 
  be 
  in 
  the 
  ooze 
  is 
  more 
  or 
  less 
  completely 
  replaced 
  by 
  

   manganese 
  ; 
  and 
  any 
  inorganic 
  body, 
  such 
  as 
  a 
  pebble 
  or 
  a 
  piece 
  of 
  pumice, 
  

   is 
  coated 
  with 
  it, 
  as 
  a 
  fine 
  black 
  mammillated 
  layer. 
  It 
  is 
  not 
  easy 
  to 
  tell 
  

   what 
  the 
  proportion 
  of 
  manganese 
  in 
  the 
  red 
  clay 
  may 
  be, 
  but 
  it 
  is 
  very 
  

   considerable. 
  At 
  station 
  160, 
  on 
  the 
  13th 
  of 
  March, 
  the 
  trawl 
  brought 
  up 
  

   nearly 
  a 
  bushel 
  of 
  nodules, 
  from 
  the 
  size 
  of 
  a 
  walnut 
  to 
  that 
  of 
  an 
  orange 
  ; 
  

   but 
  these 
  were 
  probably 
  the 
  result 
  of 
  the 
  sifting 
  of 
  a 
  large 
  quantity 
  of 
  the 
  

  

  