﻿OCEANOGRAPHY 
  — 
  STETSON 
  231 
  

  

  necessary, 
  a 
  small 
  bomb 
  loaded 
  with 
  TNT 
  is 
  dropped 
  overboard, 
  and 
  

   the 
  time 
  of 
  the 
  explosion 
  is 
  recorded 
  on 
  a 
  tape. 
  The 
  sound 
  waves, 
  

   traveling 
  through 
  the 
  water, 
  are 
  picked 
  up 
  by 
  the 
  shore 
  stations 
  and 
  

   radioed 
  back 
  to 
  the 
  ship, 
  and 
  the 
  time 
  of 
  reception 
  is 
  recorded 
  on 
  

   the 
  same 
  tape. 
  The 
  travel 
  times 
  of 
  the 
  sound 
  waves, 
  after 
  the 
  nec- 
  

   essary 
  corrections 
  have 
  been 
  applied, 
  give 
  the 
  distance 
  of 
  the 
  ship 
  

   from 
  each 
  hydrophone. 
  As 
  the 
  surveying 
  vessel 
  works 
  farther 
  and 
  

   farther 
  offshore 
  it 
  eventually 
  becomes 
  necessary 
  to 
  move 
  the 
  hydro- 
  

   phones 
  farther 
  seaward 
  as 
  well. 
  Originally 
  they 
  were 
  operated 
  from 
  

   anchored 
  vessels, 
  but 
  recently 
  buoys, 
  equipped 
  with 
  radio 
  apparatus, 
  

   have 
  taken 
  their 
  place. 
  Both, 
  of 
  course, 
  are 
  tied 
  in 
  with 
  the 
  shore 
  

   triangulation 
  stations. 
  

  

  One 
  more 
  device 
  is 
  used 
  in 
  offshore 
  surveying 
  — 
  the 
  taut-wire 
  ap- 
  

   paratus 
  which 
  was 
  originally 
  developed 
  by 
  the 
  British. 
  It 
  consists 
  

   of 
  a 
  large 
  drum 
  of 
  fine 
  wire 
  which 
  is 
  used 
  as 
  a 
  steel 
  tape 
  in 
  lengths 
  

   of 
  over 
  140 
  miles. 
  One 
  end 
  is 
  anchored 
  to 
  the 
  bottom, 
  and, 
  as 
  the 
  

   ship 
  proceeds 
  on 
  her 
  course, 
  the 
  wire 
  is 
  paid 
  out 
  over 
  a 
  sheave 
  which 
  

   registers 
  the 
  distance 
  run. 
  When 
  a 
  large 
  area 
  is 
  surveyed, 
  this 
  

   method 
  is 
  used 
  to 
  measure 
  the 
  distances 
  between 
  anchored 
  buoys 
  

   over 
  the 
  shoreward 
  portions 
  of 
  the 
  regions 
  to 
  be 
  covered, 
  as 
  it 
  can 
  

   be 
  employed 
  successfully 
  only 
  in 
  relatively 
  shallow 
  water. 
  As 
  the 
  

   work 
  progresses 
  offshore 
  it 
  is 
  replaced 
  by 
  radio-acoustic 
  ranging. 
  

  

  All 
  the 
  maritime 
  nations 
  have 
  charted 
  their 
  own 
  coastal 
  waters, 
  

   and 
  various 
  naval 
  vessels 
  have 
  done 
  valuable 
  work 
  in 
  the 
  deeper 
  ocean 
  

   basins. 
  The 
  recently 
  published 
  bathymetric 
  charts 
  of 
  the 
  East 
  In- 
  

   dian 
  seas 
  from 
  soundings 
  taken 
  by 
  the 
  Snellius 
  expedition 
  are 
  out- 
  

   standing 
  examples 
  (1934; 
  1935). 
  Not 
  only 
  do 
  they 
  clearly 
  depict 
  the 
  

   morphology 
  of 
  the 
  basins, 
  fore 
  deeps, 
  and 
  fault 
  scarps, 
  but 
  the 
  to- 
  

   pography 
  is 
  sufficiently 
  detailed 
  to 
  serve 
  as 
  the 
  basis 
  for 
  general 
  

   geological 
  discussion 
  by 
  Dr. 
  Ph. 
  H. 
  Kuenen 
  of 
  such 
  fundamental 
  

   problems 
  as 
  the 
  theories 
  concerning 
  the 
  structure 
  and 
  origin 
  of 
  island 
  

   arcs 
  and 
  fore 
  deeps, 
  so 
  well 
  exemplified 
  in 
  this 
  interesting 
  region. 
  

  

  Surveying 
  on 
  an 
  equally 
  large 
  scale 
  has 
  been 
  carried 
  out 
  in 
  the 
  

   South 
  Atlantic 
  by 
  the 
  Meteor. 
  As 
  a 
  result, 
  Stock 
  and 
  Wiist 
  have 
  

   been 
  able 
  to 
  draw 
  a 
  greatly 
  improved 
  bathymetric 
  chart 
  of 
  that 
  

   ocean 
  {Meteor 
  Expedition, 
  1935-39). 
  The 
  true 
  configuration 
  of 
  the 
  

   southern 
  extension 
  of 
  the 
  mid-Atlantic 
  ridge 
  has 
  been 
  depicted 
  for 
  the 
  

   first 
  time, 
  as 
  well 
  as 
  the 
  longitudinal 
  basins 
  on 
  either 
  side 
  of 
  it 
  which 
  

   are 
  separated 
  from 
  each 
  other 
  by 
  smaller 
  transverse 
  ridges. 
  

  

  The 
  United 
  States 
  Coast 
  and 
  Geodetic 
  Survey 
  deserves 
  great 
  credit 
  

   and 
  the 
  gratitude 
  of 
  geologists 
  everywhere 
  for 
  the 
  introduction 
  of 
  

   precise 
  methods 
  into 
  offshore 
  surveying. 
  The 
  production 
  of 
  topo- 
  

   graphic 
  maps 
  such 
  as 
  the 
  series 
  for 
  the 
  Atlantic 
  continental 
  shelf 
  and 
  

   slopes, 
  drawn 
  from 
  their 
  soundings 
  by 
  A. 
  C. 
  Veatch 
  and 
  P. 
  A. 
  Smith 
  

  

  