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  ANNUAL, 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  places 
  run 
  to 
  3,000 
  fathoms? 
  Indeed 
  there 
  is 
  one 
  sounding 
  by 
  the 
  

   U. 
  S. 
  cable 
  ship 
  Nero, 
  far 
  out 
  in 
  the 
  Pacific, 
  of 
  5,269 
  fathoms, 
  which 
  

   lacks 
  just 
  66 
  feet 
  of 
  being 
  6 
  miles. 
  So 
  Mount 
  Everest, 
  the 
  highest 
  

   mountain 
  in 
  the 
  world, 
  could 
  be 
  turned 
  upside 
  down 
  there 
  without 
  

   hitting 
  the 
  bottom 
  by 
  half 
  a 
  mile. 
  

  

  For 
  purposes 
  of 
  navigation, 
  the 
  most 
  important 
  thing 
  is 
  to 
  know 
  

   where 
  the 
  shallow 
  places 
  are, 
  and 
  just 
  how 
  shallow 
  they 
  are. 
  Gov- 
  

   ernments 
  maintain 
  coast 
  and 
  hydrographic 
  survey 
  organizations 
  for 
  

   this 
  purpose. 
  All 
  of 
  the 
  approaches 
  to 
  important 
  harbors 
  are 
  

   mapped 
  quite 
  as 
  carefully 
  as 
  the 
  land, 
  in 
  order 
  that 
  ships 
  can 
  go 
  

   safely. 
  Our 
  own 
  country 
  and 
  island 
  countries 
  like 
  Great 
  Britain 
  

   have 
  had 
  an 
  immense 
  task 
  in 
  sounding 
  and 
  surveying 
  their 
  enor- 
  

   mously 
  long 
  coast 
  lines. 
  

  

  Until 
  now 
  the 
  depths 
  less 
  than 
  20 
  fathoms 
  ( 
  120 
  feet) 
  have 
  usually 
  . 
  

   been 
  observed 
  by 
  letting 
  down 
  by 
  hand 
  from 
  stationary 
  boats 
  

   weights 
  called 
  " 
  leads 
  " 
  attached 
  to 
  cords. 
  The 
  lead 
  is 
  hollowed 
  out 
  

   at 
  the 
  bottom 
  and 
  filled 
  with 
  tallow 
  so 
  as 
  to 
  bring 
  up 
  a 
  little 
  sample 
  

   of 
  the 
  bottom, 
  and 
  prove 
  that 
  it 
  has 
  been 
  reached. 
  

  

  For 
  depths 
  over 
  20 
  fathoms, 
  steel 
  wires 
  are 
  used 
  instead 
  of 
  cords, 
  

   and 
  special 
  machines 
  for 
  unreeling 
  and 
  reeling 
  up 
  the 
  sounding 
  wire 
  

   are 
  employed. 
  As 
  the 
  depths 
  increase 
  the 
  time 
  required 
  increases, 
  

   too. 
  Of 
  course 
  the 
  ship 
  must 
  be 
  as 
  stationary 
  as 
  can 
  be 
  during 
  the 
  

   letting 
  down 
  of 
  the 
  lead. 
  If 
  the 
  sounding 
  apparatus 
  is 
  at 
  the 
  stern 
  

   she 
  can, 
  of 
  course, 
  get 
  under 
  way 
  as 
  soon 
  as 
  the 
  bottom 
  is 
  surely 
  

   reached. 
  With 
  enormously 
  great 
  depths 
  it 
  would 
  be 
  a 
  little 
  dif- 
  

   ficult 
  to 
  tell 
  just 
  when 
  this 
  tkne 
  came, 
  if 
  the 
  lead 
  was 
  not 
  extremely 
  

   heavy. 
  For 
  what 
  with 
  the 
  weight 
  of 
  the 
  wire, 
  the 
  surging 
  of 
  it 
  to 
  

   and 
  fro 
  under 
  the 
  influence 
  of 
  waves 
  and 
  currents, 
  the 
  difference 
  be- 
  

   tween 
  resting 
  on 
  the 
  bottom 
  and 
  not 
  would 
  be 
  inconspicuous 
  with 
  a 
  

   light 
  lead. 
  A 
  device 
  was 
  therefore 
  invented 
  so 
  that 
  as 
  soon 
  as 
  the 
  

   wire 
  slackened, 
  due 
  to 
  the 
  resting 
  of 
  the 
  lead 
  on 
  the 
  bottom, 
  the 
  

   sinker 
  separated. 
  Thus 
  heavy 
  sinkers 
  could 
  be 
  used 
  without 
  having 
  

   to 
  pull 
  them 
  up 
  again, 
  and 
  the 
  fact 
  that 
  they 
  were 
  detached 
  proved 
  

   that 
  the 
  bottom 
  was 
  reached. 
  

  

  There 
  is 
  another 
  sounding 
  device 
  which 
  can 
  be 
  used 
  at 
  depths 
  less 
  

   than 
  100 
  fathoms 
  which 
  does 
  not 
  require 
  the 
  ship 
  to 
  be 
  stopped 
  and 
  

   is 
  used 
  in 
  navigation. 
  The 
  lead 
  contains 
  a 
  glass 
  tube 
  closed 
  at 
  the 
  

   top 
  and 
  faintly 
  etched 
  inside 
  according 
  to 
  Benedict's 
  scheme 
  with 
  a 
  

   screw 
  of 
  about 
  40 
  threads 
  to 
  the 
  inch. 
  As 
  the 
  lead 
  sinks 
  deeper 
  and 
  

   deeper 
  the 
  pressure 
  of 
  water 
  compresses 
  and 
  forces 
  the 
  air 
  back 
  and 
  

   back 
  in 
  the 
  tube, 
  and 
  wets 
  the 
  etching 
  so 
  that 
  the 
  exact 
  amount 
  of 
  

   compression 
  of 
  the 
  air 
  is 
  shown. 
  This 
  is 
  read 
  off 
  on 
  a 
  scale 
  which 
  

   indicates 
  the 
  depth. 
  Of 
  course 
  with 
  the 
  ship 
  moving, 
  the 
  bottom 
  can 
  

   be 
  surely 
  felt 
  by 
  the 
  twitching 
  of 
  the 
  cord. 
  

  

  