﻿7G8 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [10] 
  

  

  It 
  may 
  be 
  added 
  that 
  in 
  the 
  majority 
  of 
  cases 
  we 
  have 
  solidified 
  the 
  

   sediments 
  and 
  formed 
  them 
  into 
  thin 
  slides 
  for 
  microscopic 
  examina- 
  

   tion, 
  and 
  that 
  at 
  all 
  times 
  the 
  examination 
  by 
  transmitted 
  light 
  has 
  been 
  

   carried 
  on 
  at 
  the 
  same 
  time 
  as 
  the 
  examination 
  by 
  reflected 
  light. 
  Each 
  

   description 
  is 
  followed 
  by 
  notes 
  upon 
  the 
  dredging 
  or 
  sounding, 
  upon 
  

   the 
  animals 
  collected, 
  and 
  a 
  discussion 
  of 
  the 
  analysis 
  whenever 
  a 
  com- 
  

   plete 
  analysis 
  has 
  been 
  made, 
  which 
  is 
  always 
  the 
  case 
  with 
  typical 
  

   samples 
  of 
  the 
  deposits. 
  

  

  Kinds 
  of 
  deposits. 
  — 
  We 
  now 
  proceed 
  to 
  the 
  description 
  of 
  the 
  va- 
  

   rious 
  types 
  of 
  deposits 
  into 
  which 
  it 
  is 
  proposed 
  to 
  divide 
  the 
  marine 
  

   formations 
  that 
  are 
  now 
  taking 
  place 
  in 
  the 
  deeper 
  water 
  of 
  the 
  various 
  

   oceans 
  and 
  seas. 
  We 
  will 
  speak 
  first 
  of 
  those 
  which 
  are 
  met 
  with 
  in 
  

   the 
  deeper 
  water 
  of 
  inland 
  seas, 
  and 
  around 
  the 
  coasts 
  of 
  continents 
  

   and 
  islands, 
  and 
  afterwards 
  of 
  those 
  which 
  are 
  found 
  in 
  the 
  abysmal 
  

   regions 
  of 
  the 
  great 
  oceans. 
  Those 
  coast 
  formations 
  which 
  are 
  being 
  

   laid 
  down 
  on 
  the 
  shores, 
  or 
  in 
  very 
  shallow 
  water, 
  and 
  which 
  have 
  been 
  

   somewhat 
  carefully 
  described 
  previous 
  to 
  the 
  recent 
  deep-sea 
  explora- 
  

   tions, 
  are 
  here 
  neglected. 
  

  

  A 
  study 
  of 
  the 
  collections 
  made 
  by 
  the 
  Challenger 
  and 
  other 
  expedi- 
  

   tions 
  shows 
  — 
  

  

  (1.) 
  That 
  in 
  the 
  deeper 
  water 
  around 
  continents 
  and 
  islands 
  which 
  

   are 
  neither 
  of 
  volcanic 
  nor 
  coral 
  origin, 
  the 
  sediments 
  are 
  essentially 
  

   composed 
  of 
  a 
  mixture 
  of 
  sandy 
  and 
  amorphous 
  matter, 
  with 
  a 
  few 
  re- 
  

   mains 
  of 
  surface 
  organisms, 
  to 
  which 
  we 
  give 
  the 
  name 
  of 
  muds, 
  and 
  

   which 
  may 
  be 
  distinguished 
  microscopically 
  by 
  their 
  color. 
  We 
  dis- 
  

   tinguish 
  them 
  by 
  the 
  names 
  blue, 
  red, 
  and 
  green 
  muds. 
  

  

  (2.) 
  Around 
  volcanic 
  islands 
  the 
  deposits 
  are 
  chiefly 
  composed 
  of 
  

  

  mineral 
  fragments 
  derived 
  from 
  the 
  decomposition 
  of 
  volcanic 
  rocks. 
  

  

  These, 
  according 
  to 
  the 
  size 
  of 
  the 
  grains, 
  are 
  called 
  volcanic 
  muds 
  or 
  

  

  sands. 
  

  

  (3.) 
  Near 
  coral 
  islands 
  and 
  along 
  shores 
  fringed 
  by 
  coral 
  reefs 
  the 
  

  

  deposits 
  are 
  calcareous, 
  derived 
  chiefly 
  from 
  the 
  disintegration 
  of 
  the 
  

   neighboring 
  reefs, 
  but 
  they 
  receive 
  large 
  additions 
  from 
  shells 
  and 
  

   skeletons 
  of 
  pelagic 
  organism, 
  as 
  well 
  as 
  from 
  animals 
  living 
  at 
  the 
  

   bottom. 
  These 
  are 
  named, 
  according 
  to 
  circumstances, 
  coral 
  or 
  coral- 
  

   line 
  muds 
  and 
  sands. 
  

  

  Let 
  us 
  now 
  see 
  what 
  are 
  the 
  chief 
  characteristics 
  of 
  each 
  of 
  these 
  de- 
  

   posits. 
  

  

  Blue 
  mud 
  is 
  the 
  most 
  extensive 
  deposit 
  now 
  forming 
  around 
  the 
  great 
  

   continents 
  and 
  continental 
  islands 
  and 
  in 
  all 
  inclosed 
  or 
  partially 
  iu- 
  

   closed 
  seas. 
  It 
  is 
  characterized 
  by 
  the 
  slaty 
  color 
  which 
  passes 
  in 
  most 
  

   cases 
  into 
  a 
  thin 
  layer 
  of 
  a 
  reddish 
  color 
  at 
  the 
  upper 
  surface. 
  These 
  

   deposits 
  are 
  colored 
  blue 
  by 
  organic 
  matter 
  in 
  a 
  state 
  of 
  decomposition 
  

   and 
  frequently 
  give 
  off 
  an 
  odor 
  of 
  sulphureted 
  hydrogen. 
  When 
  dried 
  

   a 
  blue 
  mud 
  is 
  grayish 
  in 
  color 
  and 
  rarely 
  or 
  never 
  has 
  the 
  plasticity 
  

   and 
  compactness 
  of 
  a 
  true 
  clay. 
  It 
  is 
  finely 
  granular 
  and 
  occasionally 
  

  

  