﻿136 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  117 
  million 
  tons 
  of 
  common 
  salt, 
  and 
  some 
  300,000 
  tons 
  of 
  bromine, 
  

   which 
  is 
  present 
  to 
  the 
  extent 
  of 
  less 
  than 
  70 
  parts 
  per 
  1 
  million 
  of 
  sea 
  

   water. 
  

  

  Such 
  quantities, 
  if 
  extracted, 
  would 
  satisfy 
  the 
  world 
  for 
  a 
  con- 
  

   siderable 
  time, 
  while 
  a 
  cubic 
  mile 
  of 
  sea 
  is 
  not 
  out 
  of 
  range 
  of 
  a 
  

   single 
  plant 
  located 
  on 
  an 
  ocean 
  seaboard. 
  The 
  sea 
  clearly 
  forms 
  

   an 
  inexhaustible 
  storehouse 
  of 
  minerals, 
  provided 
  that 
  man 
  can 
  find 
  

   out 
  how 
  to 
  recover 
  them 
  individually 
  at 
  prices 
  comparable 
  with 
  the 
  

   cost 
  of 
  winning 
  the 
  same 
  substances 
  from 
  the 
  earth. 
  

  

  THE 
  COMPOSITION 
  OF 
  OCEANS 
  

  

  Before 
  describing 
  what 
  has 
  been 
  done 
  in 
  this 
  direction, 
  it 
  is 
  well 
  

   to 
  devote 
  a 
  few 
  words 
  to 
  the 
  composition 
  of 
  the 
  oceans. 
  One 
  theory 
  

   is 
  that 
  they 
  have 
  been 
  salt 
  from 
  the 
  beginning 
  rather 
  than 
  the 
  alter- 
  

   native 
  theory 
  that 
  they 
  have 
  become 
  so 
  by 
  washing 
  out 
  of 
  salts 
  from 
  

   the 
  land 
  and 
  gradual 
  concentration 
  by 
  evaporation 
  of 
  the 
  oceans. 
  

   This 
  hypothesis 
  is 
  based 
  on 
  the 
  great 
  similarity 
  between 
  the 
  salts 
  of 
  

   the 
  ocean 
  and 
  the 
  gaseous 
  products 
  of 
  volcanic 
  eruptions 
  rich 
  in 
  chlo- 
  

   rides 
  and 
  sulfates 
  of 
  all 
  kinds. 
  The 
  theory 
  explains 
  the 
  main 
  con- 
  

   stituents, 
  though 
  it 
  does 
  not 
  necessarily 
  apply 
  to 
  the 
  trace 
  elements 
  

   where 
  any 
  postulate 
  of 
  constancy 
  of 
  composition 
  is 
  untenable. 
  

  

  Apparently 
  the 
  first 
  quantitative 
  analyses 
  of 
  sea 
  water 
  were 
  made 
  

   by 
  Lavoisier 
  in 
  1872. 
  

  

  It 
  transpires 
  that 
  the 
  variations 
  in 
  the 
  proportions 
  of 
  individual 
  

   salts 
  to 
  the 
  total 
  salts 
  are 
  very 
  small 
  ; 
  sea 
  water 
  may 
  be 
  regarded 
  as 
  of 
  

   constant 
  composition, 
  the 
  individual 
  ingredients 
  being 
  considerably 
  

   dissociated 
  in 
  the 
  dilute 
  solution. 
  This 
  interdiffusion 
  accounts 
  easily 
  

   for 
  the 
  uniformity 
  of 
  composition 
  of 
  sea 
  water 
  throughout 
  the 
  

   whole 
  ocean, 
  so 
  that 
  the 
  only 
  appreciable 
  difference 
  from 
  point 
  to 
  

   point 
  is 
  the 
  total 
  salinity 
  of 
  the 
  mixed 
  solutions. 
  

  

  In 
  each 
  of 
  the 
  three 
  oceans 
  the 
  salinity 
  is 
  lower 
  in 
  the 
  equatorial 
  

   regions 
  where 
  the 
  rainfall 
  is 
  high 
  ; 
  there 
  are 
  two 
  maxima 
  — 
  one 
  in 
  the 
  

   north, 
  the 
  other 
  in 
  the 
  south 
  tropical 
  belts 
  where 
  evaporation 
  pre- 
  

   dominates 
  ; 
  at 
  the 
  Poles 
  there 
  are 
  regions 
  of 
  lower 
  salinity. 
  The 
  North 
  

   Atlantic 
  maximum 
  is 
  the 
  highest 
  at 
  37.9 
  parts 
  per 
  1,000 
  salinity; 
  as 
  

   a 
  whole, 
  the 
  Atlantic 
  has 
  the 
  highest 
  salinity 
  of 
  35.37. 
  The 
  average 
  

   of 
  the 
  whole 
  surface 
  of 
  the 
  oceans 
  may 
  be 
  taken 
  as 
  34.5. 
  There 
  is 
  a 
  gen- 
  

   eral 
  increase 
  of 
  salinity 
  with 
  depth. 
  

  

  Common 
  salt 
  is 
  essential 
  to 
  both 
  man 
  and 
  beast 
  ; 
  we 
  need 
  more 
  salt 
  

   as 
  the 
  proportion 
  of 
  meat 
  we 
  eat 
  diminishes. 
  In 
  Britain 
  and 
  else- 
  

   where 
  there 
  are 
  large 
  deposits 
  of 
  pure 
  salt 
  resulting 
  from 
  the 
  drying 
  

   up 
  of 
  inland 
  seas 
  in 
  past 
  geological 
  ages. 
  This 
  is 
  recovered 
  by 
  mining 
  

   or 
  more 
  generally 
  by 
  dissolving 
  the 
  salt 
  underground, 
  pumping 
  up 
  

   the 
  brine, 
  and 
  evaporating 
  it. 
  The 
  export 
  of 
  salt 
  from 
  England 
  has 
  

  

  