﻿[3] 
  ON 
  DEEP-SEA 
  DEPOSITS. 
  761 
  

  

  observations 
  made 
  by 
  the 
  Challenger, 
  we 
  have 
  had 
  for 
  examination 
  

   material 
  collected 
  by 
  other 
  British 
  ships, 
  such 
  as 
  the 
  Porcupine, 
  Bull- 
  

   dog 
  - 
  , 
  Valorous, 
  Nassau, 
  Swallow, 
  Dove 
  ; 
  and, 
  through 
  Professor 
  Mohn, 
  

   by 
  the 
  Norwegian 
  North 
  Atlantic 
  expedition. 
  Again, 
  through 
  the 
  lib- 
  

   erality 
  of 
  the 
  United 
  States 
  Coast 
  Survey 
  and 
  Mr. 
  Agassiz, 
  the 
  material 
  

   amassed 
  in 
  the 
  splendid 
  series 
  of 
  soundings 
  taken 
  by 
  the 
  American 
  

   ships 
  Tnscarora, 
  Blake, 
  and 
  Gettysburg, 
  were 
  placed 
  in 
  our 
  hands. 
  

   The 
  results 
  at 
  which 
  we 
  have 
  arrived 
  may 
  therefore 
  be 
  said 
  to 
  have 
  

   been 
  derived 
  from 
  a 
  study 
  of 
  all 
  the 
  important 
  available 
  material. 
  

  

  The 
  work 
  connected 
  with 
  the 
  examination 
  and 
  description 
  of 
  these 
  

   large 
  collections 
  is 
  not 
  yet 
  completed, 
  but 
  it 
  is 
  sufficiently 
  advanced 
  to 
  

   permit 
  some 
  general 
  conclusions 
  to 
  be 
  drawn 
  which 
  appear 
  to 
  be 
  of 
  con- 
  

   siderable 
  importance. 
  In 
  addition 
  to 
  descriptions 
  and 
  results, 
  we 
  shall 
  

   briefly 
  state 
  the 
  methods 
  we 
  have 
  adopted 
  in 
  the 
  study. 
  All 
  the 
  details 
  

   of 
  our 
  research 
  will 
  be 
  given 
  in 
  the 
  report 
  on 
  the 
  deep-sea 
  deposits 
  in 
  

   the 
  Challenger 
  series, 
  which 
  will 
  be 
  accompanied 
  by 
  charts 
  indicating 
  

   the 
  distribution, 
  plates 
  showing 
  the 
  principal 
  types 
  of 
  deposits 
  as 
  seen 
  

   by 
  the 
  microscope, 
  and 
  numerous 
  analyses 
  giving 
  the 
  chemical 
  composi- 
  

   tion 
  and 
  its 
  relation 
  to 
  the 
  mineralogical 
  composition. 
  The 
  description 
  

   of 
  each 
  sediment 
  will 
  be 
  accompanied 
  by 
  an 
  enumeration 
  of 
  the 
  organ- 
  

   isms 
  dredged 
  with 
  the 
  sample, 
  so 
  as 
  to 
  furnish 
  all 
  the 
  biological 
  and 
  

   mineralogical 
  information 
  which 
  we 
  possess 
  on 
  deep-sea 
  deposits, 
  and 
  

   finally, 
  we 
  shall 
  endeavor 
  to 
  establish 
  general 
  conclusions 
  which 
  can 
  

   only 
  be 
  indicated 
  at 
  present. 
  

  

  Before 
  entering 
  on 
  the 
  subject, 
  we 
  believe 
  it 
  right 
  to 
  point 
  out 
  the 
  

   difficulties 
  which 
  necessarily 
  accompany 
  such 
  a 
  research 
  as 
  the 
  one 
  now 
  

   under 
  consideration, 
  difficulties 
  which 
  arise 
  often 
  in 
  part 
  from 
  the 
  small 
  

   quantity 
  of 
  the 
  substance 
  at 
  our 
  disposal, 
  but 
  also 
  from 
  the 
  very 
  nature 
  

   of 
  the 
  deposit. 
  Since 
  we 
  have 
  endeavored 
  to 
  determine, 
  with 
  great 
  

   exactitude, 
  the 
  composition 
  of 
  the 
  deposit 
  at 
  any 
  given 
  point, 
  we 
  have, 
  

   whenever 
  possible, 
  taken 
  the 
  sample 
  collected 
  in 
  the 
  sounding-tube. 
  

   That 
  procured 
  by 
  the 
  trawl 
  or 
  dredge, 
  although 
  usually 
  much 
  larger, 
  

   is 
  not 
  considered 
  so 
  satisfactory 
  on 
  account 
  of 
  the 
  washing 
  and 
  sorting 
  

   to 
  which 
  the 
  deposit 
  has 
  been 
  subjected 
  while 
  being 
  hauled 
  through 
  a 
  

   great 
  depth 
  of 
  water. 
  We 
  have, 
  however, 
  always 
  examined 
  carefully 
  

   the 
  contents 
  of 
  these 
  instruments, 
  although 
  we 
  do 
  not 
  think 
  the 
  mate- 
  

   rial 
  gives 
  such 
  a 
  just 
  idea 
  of 
  the 
  deposit 
  as 
  the 
  sample 
  collected 
  by 
  the 
  

   sounding-tube. 
  The 
  material 
  collected 
  by 
  the 
  last-named 
  instrument 
  

   has 
  been 
  taken 
  as 
  the 
  basis 
  of 
  our 
  investigations, 
  although 
  the 
  small 
  

   quantity 
  often 
  gives 
  to 
  it 
  an 
  inherent 
  difficulty. 
  It 
  was 
  the 
  small 
  quan- 
  

   tity 
  of 
  substance 
  collected 
  by 
  the 
  sounding-tube 
  in 
  early 
  expeditious 
  

   which 
  prevented 
  the 
  first 
  observers 
  from 
  arriving 
  at 
  any 
  definite 
  re- 
  

   sults, 
  but 
  when 
  such 
  small 
  samples 
  are 
  supplemented 
  by 
  occasional 
  

   large 
  hauls 
  from 
  the 
  dredge 
  or 
  trawl, 
  they 
  become 
  much 
  more 
  valuable 
  

   and 
  indicative 
  of 
  the 
  nature 
  of 
  the 
  deposit 
  as 
  a 
  whole. 
  Not 
  only 
  the 
  

   scantiness 
  of 
  the 
  material, 
  but 
  the 
  small 
  size 
  of 
  the 
  grains, 
  which 
  in 
  

  

  