﻿[15] 
  ON 
  DEEP-SEA 
  DEPOSITS. 
  773 
  

  

  that 
  it 
  exists 
  everywhere 
  in 
  the 
  abysmal 
  regions 
  of 
  the 
  ocean 
  basins, 
  

   for 
  the 
  residue 
  in 
  the 
  organic 
  deposits, 
  which 
  has 
  been 
  described 
  under 
  

   the 
  name 
  Globigerina, 
  Pteropod, 
  and 
  Radiolarian 
  ooze, 
  is 
  nothing 
  else 
  

   than 
  the 
  red 
  clay. 
  However, 
  this 
  deposit 
  only 
  appears 
  in 
  its 
  character- 
  

   istic 
  form 
  in 
  those 
  areas 
  where 
  the 
  terrigenous 
  minerals 
  and 
  calcareous 
  

   and 
  siliceous 
  organisms 
  disappear 
  to 
  a 
  greater 
  or 
  less 
  extent 
  from 
  the 
  

   bottom. 
  It 
  is 
  in 
  the 
  central 
  regions 
  of 
  the 
  Pacific 
  that 
  we 
  meet 
  with 
  

   .the 
  typical 
  examples. 
  Like 
  other 
  marine 
  deposits 
  this 
  one 
  passes 
  liter- 
  

   ally, 
  according 
  to 
  position 
  and 
  depth, 
  into 
  the 
  adjacent 
  kind 
  of 
  deep- 
  

   sea 
  ooze 
  or 
  mud. 
  

  

  The 
  argillaceous 
  matters 
  are 
  of 
  a 
  more 
  or 
  less 
  deep 
  brown 
  tint 
  from 
  

   the 
  presence 
  of 
  the 
  oxides 
  of 
  iron 
  and 
  manganese. 
  In 
  the 
  typical 
  ex- 
  

   amples 
  no 
  mineralogical 
  species 
  can 
  be 
  distinguished 
  by 
  the 
  naked 
  

   eye, 
  for 
  the 
  grains 
  are 
  exceedingly 
  fine 
  and 
  of 
  nearly 
  uniform 
  dimen- 
  

   sions, 
  rarely 
  exceeding 
  0.05 
  u,m 
  in 
  diameter. 
  It 
  is 
  plastic 
  and 
  greasy 
  to 
  

   the 
  touch 
  ; 
  when 
  dried 
  it 
  coagulates 
  into 
  lumps 
  so 
  coherent 
  that 
  con- 
  

   siderable 
  force 
  must 
  be 
  employed 
  to 
  break 
  them. 
  It 
  gives 
  the 
  brilliant 
  

   streak 
  of 
  clay, 
  and 
  breaks 
  down 
  in 
  water. 
  The 
  pyrognostic 
  properties 
  

   show 
  that 
  we 
  are 
  not 
  dealing 
  with 
  a 
  pure 
  clay, 
  for 
  it 
  fuses 
  easily 
  before 
  

   the 
  blow-pipe 
  into 
  a 
  magnetic 
  bead. 
  

  

  Under 
  the 
  term 
  "red 
  clay" 
  are 
  comprised 
  three 
  deposits 
  in 
  which 
  the 
  

   characters 
  of 
  clay 
  are 
  not 
  well 
  pronounced, 
  but 
  which 
  are 
  mainly 
  com- 
  

   posed 
  of 
  minute 
  particles 
  of 
  pumice 
  and 
  other 
  volcanic 
  material 
  which, 
  

   owing 
  to 
  their 
  relatively 
  recent 
  deposition, 
  have 
  not 
  undergone 
  great 
  

   alterations. 
  If 
  we 
  calculate 
  the 
  analyses 
  of 
  red 
  clay, 
  it 
  will 
  be 
  seen, 
  

   moreover, 
  that 
  the 
  silicate 
  of 
  alumina 
  present 
  as 
  clay 
  (2 
  Si0 
  2 
  , 
  Al 
  2 
  3 
  -f 
  2 
  

   H 
  2 
  0) 
  comprises 
  only 
  a 
  relatively 
  small 
  portion 
  of 
  the 
  sediment; 
  the 
  cal- 
  

   culation 
  shows 
  always 
  an 
  excess 
  of 
  free 
  silica, 
  which 
  is 
  attributed 
  chiefly 
  

   to 
  the 
  presence 
  of 
  siliceous 
  organisms. 
  

  

  Microscopic 
  examination 
  shows 
  that 
  a 
  red 
  clay 
  consists 
  of 
  argillaceous 
  

   matter, 
  minute 
  mineral 
  particles, 
  and 
  fragments 
  of 
  siliceous 
  organisms; 
  

   in 
  a 
  word, 
  it 
  is 
  in 
  all 
  respects 
  identical 
  with 
  the 
  residue 
  of 
  the 
  organic 
  

   oozes. 
  The 
  mineral 
  particles 
  are, 
  for 
  the 
  greater 
  part, 
  of 
  volcanic 
  origin, 
  

   except 
  in 
  those 
  cases 
  where 
  continental 
  matters 
  are 
  transported 
  by 
  

   floating 
  ice, 
  or 
  where 
  the 
  sand 
  of 
  deserts 
  has 
  been 
  carried 
  to 
  great 
  dis- 
  

   tances 
  by 
  winds. 
  These 
  volcanic 
  minerals 
  are 
  the 
  same 
  constituent 
  

   minerals 
  of 
  modern 
  eruptive 
  rocks 
  enumerated 
  in 
  the 
  description 
  of 
  

   volcanic 
  muds 
  and 
  sands. 
  In 
  the 
  great 
  majority 
  of 
  cases 
  they 
  are 
  ac- 
  

   companied 
  by 
  fragments 
  of 
  lapilla, 
  and 
  of 
  puinice 
  more 
  or 
  less 
  altered. 
  

   Vitreous 
  volcanic 
  matters 
  belonging 
  to 
  the 
  acid 
  and 
  basic 
  series 
  of 
  rocks 
  

   predominate 
  in 
  the 
  regions 
  where 
  the 
  red 
  clay 
  has 
  its 
  greatest 
  develop- 
  

   ment, 
  and 
  it 
  will 
  be 
  seen 
  presently 
  that 
  the 
  most 
  characteristic 
  decom- 
  

   positions 
  which 
  there 
  take 
  place 
  are 
  associated 
  with 
  pyroxenic 
  lavas. 
  

  

  Associated 
  with 
  the 
  red 
  clay 
  are 
  almost 
  always 
  found 
  concretions 
  

   and 
  microscopic 
  particles 
  of 
  the 
  oxides 
  of 
  iron 
  and 
  manganese, 
  to 
  which 
  

   the 
  deposit 
  owes 
  its 
  color. 
  Again, 
  in 
  the 
  typical 
  examples 
  of 
  the 
  de- 
  

  

  