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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  experiments 
  were 
  carried 
  out 
  in 
  the 
  shallow 
  water 
  of 
  our 
  east 
  coast 
  

   continental 
  shelf 
  by 
  Dr. 
  Maurice 
  Ewing 
  (1937) 
  5 
  years 
  ago. 
  The 
  tech- 
  

   nique 
  for 
  shallow 
  water 
  can 
  be 
  regarded 
  as 
  nearly 
  perfected, 
  while 
  

   that 
  for 
  deep 
  water 
  is 
  still 
  in 
  the 
  experimental 
  stage. 
  A 
  new 
  develop- 
  

   ment 
  in 
  the 
  technique 
  for 
  deep-water 
  work 
  is 
  the 
  use 
  of 
  floats 
  filled 
  

   with 
  an 
  oil 
  of 
  low 
  density 
  for 
  bringing 
  the 
  instruments 
  to 
  the 
  surface, 
  

   thereby 
  dispensing 
  with 
  a 
  long 
  wire 
  rope 
  which 
  has 
  many 
  disadvan- 
  

   tages. 
  The 
  first 
  plans, 
  as 
  described 
  by 
  Ewing 
  (1938), 
  have 
  since 
  been 
  

   greatly 
  modified, 
  though 
  the 
  principle 
  remains 
  the 
  same. 
  

  

  A 
  profile 
  consisting 
  of 
  four 
  sea 
  stations 
  has 
  been 
  run 
  from 
  Cape 
  

   Henry, 
  Va., 
  across 
  the 
  shelf 
  to 
  the 
  continental 
  margin, 
  and 
  while, 
  of 
  

   course, 
  one 
  profile 
  is 
  far 
  from 
  being 
  a 
  complete 
  picture, 
  it 
  has 
  

   demonstrated 
  that 
  the 
  method 
  is 
  a 
  usable 
  one 
  and 
  that 
  a 
  new 
  tool 
  

   has 
  been 
  acquired. 
  A 
  thickness 
  of 
  the 
  order 
  of 
  12,000 
  feet 
  of 
  un- 
  

   consolidated 
  and 
  semiconsolidated 
  sediments 
  is 
  found 
  at 
  the 
  conti- 
  

   nental 
  margin 
  over 
  rocks 
  which 
  registered 
  much 
  higher 
  velocities. 
  

   This 
  presumably 
  represents 
  the 
  thickened 
  seaward 
  extension 
  of 
  the 
  

   Coastal 
  Plane 
  monocline 
  lying 
  above 
  the 
  relatively 
  flat 
  basement 
  

   complex, 
  which 
  itself 
  has 
  a 
  seaward 
  dip. 
  The 
  same 
  relationships 
  

   which 
  have 
  been 
  observed 
  in 
  the 
  subaerial 
  portion 
  of 
  the 
  Coastal 
  

   Plain 
  are 
  apparently 
  continued 
  beneath 
  the 
  sea. 
  The 
  east 
  coast 
  shelf, 
  

   with 
  its 
  relatively 
  simple 
  structure 
  and 
  the 
  presence 
  of 
  numerous 
  

   deep 
  artesian 
  wells 
  close 
  to 
  the 
  shore 
  line, 
  is 
  a 
  particularly 
  favorable 
  

   place 
  for 
  the 
  development 
  of 
  this 
  new 
  technique. 
  

  

  Kecently 
  Drs. 
  E. 
  C. 
  Bullard 
  and 
  T. 
  F. 
  Gaskell 
  have 
  used 
  the 
  same 
  

   method 
  in 
  the 
  approaches 
  to 
  the 
  English 
  Channel 
  out 
  to 
  a 
  point 
  175 
  

   miles 
  west-southwest 
  of 
  the 
  Lizard. 
  At 
  the 
  station 
  nearest 
  shore 
  it 
  

   is 
  thought 
  that 
  an 
  extension 
  of 
  the 
  Triassic 
  is 
  picked 
  up. 
  Farther 
  

   out 
  unconsolidated 
  sediments 
  were 
  encountered 
  over 
  an 
  igneous 
  

   basement, 
  but 
  they 
  are 
  relatively 
  thin 
  in 
  comparison 
  with 
  the 
  same 
  

   type 
  of 
  deposit 
  found 
  off 
  the 
  east 
  coast 
  of 
  the 
  United 
  States. 
  

  

  It 
  is 
  at 
  present 
  impossible 
  to 
  predict 
  how 
  far 
  offshore 
  the 
  work 
  

   can 
  be 
  carried 
  and 
  still 
  retain 
  its 
  significance 
  from 
  a 
  structural 
  point 
  

   of 
  view, 
  because 
  with 
  increasing 
  distance 
  from 
  the 
  known 
  strati- 
  

   graphic 
  column, 
  which 
  must 
  be 
  constantly 
  used 
  as 
  a 
  check, 
  the 
  results 
  

   are 
  more 
  uncertain. 
  This 
  will 
  be 
  even 
  more 
  of 
  a 
  limiting 
  factor 
  in 
  

   regions 
  where 
  the 
  structure 
  is 
  complicated. 
  Deep 
  water 
  enormously 
  

   increased 
  the 
  difficulties. 
  This 
  of 
  course 
  is 
  true 
  of 
  any 
  operation 
  

   carried 
  out 
  on 
  shipboard. 
  However, 
  even 
  though 
  it 
  will 
  never 
  be 
  

   possible 
  to 
  work 
  at 
  sea 
  with 
  the 
  same 
  precision 
  that 
  can 
  be 
  attained 
  

   ashore, 
  or 
  to 
  make 
  as 
  close 
  a 
  network 
  of 
  stations, 
  or 
  get 
  in 
  as 
  many 
  

   shot 
  points, 
  this 
  should 
  be 
  no 
  deterrent 
  to 
  future 
  activity 
  in 
  this 
  partic- 
  

   ular 
  field, 
  for 
  the 
  same 
  criticism 
  can 
  be 
  leveled 
  at 
  any 
  kind 
  of 
  

   oceanographic 
  endeavor. 
  

  

  