﻿26 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  Louisiana 
  Petroleum 
  and 
  Coal 
  Oil 
  Co. 
  had 
  reached 
  a 
  depth 
  of 
  

   1,230 
  feet 
  and 
  Dr. 
  Kirkman's 
  well 
  was 
  450 
  feet 
  deep. 
  Hilgard 
  

   interprets 
  and 
  correlates 
  the 
  two 
  as 
  shown 
  on 
  p. 
  25. 
  

  

  Hilgard 
  read 
  before 
  the 
  Troy 
  meeting 
  of 
  the 
  American 
  Asso- 
  

   ciation 
  1869, 
  a 
  paper 
  "On 
  the 
  Geology 
  of 
  the 
  Delta 
  and 
  the 
  

   Mud-lumps 
  of 
  the 
  Passes 
  of 
  the 
  Mississippi.* 
  Concerning 
  the 
  

   delta 
  plain 
  as 
  a 
  whole 
  he 
  believes 
  that 
  the 
  river 
  deposits 
  cover 
  it 
  

   to 
  but 
  a 
  " 
  comparatively 
  insignificant 
  depth. 
  "f 
  He 
  has 
  found 
  

   the 
  Orange 
  sand 
  beds 
  in 
  the 
  Calcasieu 
  well 
  about 
  100 
  feet 
  in 
  

   thickness, 
  lying 
  below 
  a 
  350 
  feet 
  stratum 
  of 
  Port 
  Hudson. 
  The 
  

   latter 
  beds 
  are 
  found 
  to 
  resemble 
  those 
  in 
  the 
  New 
  Orleans 
  well, 
  

   extending 
  to 
  ai 
  depth 
  of 
  630 
  feet. 
  Sir 
  Charles 
  Lyell's 
  intima- 
  

   tion 
  that 
  the 
  beds 
  were 
  for 
  the 
  most 
  part 
  of 
  a 
  delta 
  formation 
  

   is 
  again 
  questioned 
  and 
  proven 
  false 
  by 
  the 
  microscopic 
  and 
  

   macroscopic 
  fossils 
  of 
  marine 
  origin 
  found 
  in 
  them. 
  

  

  The 
  alluvium 
  about 
  New 
  Orleans 
  varies 
  usually 
  from 
  31 
  to 
  56 
  

   feet 
  in 
  thickness 
  beneath 
  which 
  or 
  at 
  the 
  base 
  of 
  which 
  is 
  a 
  

   .stratum 
  of 
  mud 
  in 
  which 
  combustible 
  gas 
  is 
  frequently 
  found. 
  

   This 
  is 
  of 
  indifferent 
  quality 
  as 
  shown 
  by 
  analysis 
  (p. 
  245). 
  

   Accompanying 
  this 
  flow 
  of 
  gas 
  are 
  streams 
  of 
  > 
  water 
  and 
  mud 
  

   making 
  artificial 
  mud-lumps 
  of 
  sometimes 
  considerable 
  dimen- 
  

   sions 
  (p. 
  368). 
  The 
  question 
  of 
  mud-lumps 
  is 
  taken 
  up 
  and 
  

   figures 
  illustrating 
  their 
  growth 
  and 
  decay 
  are 
  given 
  (pp. 
  356- 
  

   368). 
  Their 
  origin 
  is 
  discussed 
  at 
  length 
  (pp. 
  425-435) 
  and 
  

   analyses 
  of 
  waters 
  given. 
  

  

  In 
  Hilgard's 
  report 
  on 
  the 
  material 
  obtained 
  from 
  the 
  New 
  

   Orleans 
  well 
  (bored 
  1856) 
  published 
  in 
  1870,]; 
  he 
  maintains 
  that 
  

   the 
  distribution 
  and 
  kind 
  of 
  molluscan 
  species 
  identified 
  show 
  

   that 
  at 
  least 
  the 
  lower 
  510 
  feet 
  of 
  the 
  well 
  (630 
  feet 
  deep) 
  belongs 
  

   to 
  one 
  and 
  the 
  same 
  formation. 
  It 
  is 
  not 
  a 
  delta 
  deposit. 
  It 
  is 
  

   the 
  Port 
  Hudson 
  formation. 
  A 
  carefully 
  drawn 
  section 
  of 
  the 
  

   well 
  accompanies 
  this 
  report. 
  

  

  Before 
  the 
  American 
  Association 
  in 
  187 
  1, 
  Hilgard 
  read 
  a 
  paper 
  

   " 
  On 
  the 
  Geological 
  History 
  of 
  the 
  Gulf 
  of 
  Mexico."* 
  In 
  this 
  

   paper 
  a 
  Cretaceous 
  " 
  backbone 
  " 
  (p. 
  393) 
  is 
  said 
  to 
  pass 
  through 
  

  

  *See 
  Am. 
  Jour. 
  Sci., 
  vol. 
  i, 
  1870, 
  pp. 
  238-246, 
  356-368, 
  425-435- 
  

  

  t 
  Ibid 
  p. 
  239. 
  

  

  j 
  Kept. 
  Chief 
  Eng., 
  1870, 
  pp. 
  352-361. 
  

  

  *Am. 
  Jour. 
  Sci., 
  vol. 
  2, 
  1871, 
  pp. 
  391-404. 
  

  

  