﻿I] 
  Historical 
  Review 
  : 
  Second 
  Period 
  

  

  35 
  

  

  the 
  State, 
  the 
  first 
  and 
  only 
  geological 
  state 
  map 
  thus 
  far 
  pub- 
  

   lished. 
  He 
  correlates 
  the 
  " 
  Mansfield 
  group" 
  with 
  the 
  marine 
  

   Jackson, 
  regarding 
  their 
  diflference 
  in 
  appearance 
  as 
  due 
  to 
  local 
  

   conditions 
  in 
  deposition 
  instead 
  of 
  difference 
  in 
  time 
  of 
  deposit. 
  

  

  The 
  Claiborne 
  stage 
  is 
  still 
  unidentified 
  in 
  the 
  State 
  ; 
  all 
  

   localities 
  now 
  known 
  to 
  belong 
  to 
  the 
  Lower 
  Claiborne 
  are 
  here 
  

   referred 
  to 
  the 
  Jackson 
  or 
  Vicksburg 
  stages. 
  A 
  long 
  list 
  of 
  

   Jackson 
  fossils 
  is 
  given, 
  likewise 
  a 
  less 
  exhaustive 
  one 
  of 
  the 
  

   Vicksburg. 
  

  

  This 
  report 
  cannot 
  be 
  regarded 
  as 
  more 
  than 
  a 
  restatement 
  of 
  

   the 
  more 
  important 
  facts 
  of 
  the 
  first 
  with 
  some 
  additions 
  and 
  

   corrections 
  as 
  noted 
  above. 
  

  

  The 
  third 
  Annual 
  Report 
  of 
  Dr. 
  Hopkins 
  is 
  devoted 
  almost 
  

   entirely 
  to 
  a 
  discussion 
  of 
  the 
  newer 
  formations 
  from 
  the 
  ' 
  ' 
  Drift, 
  ' 
  ' 
  

   (now 
  called 
  the 
  Lafayette) 
  upwards. 
  In 
  this 
  report 
  he 
  departs 
  

   from 
  the 
  view 
  which 
  he 
  has 
  heretofore 
  advocated 
  of 
  the 
  com- 
  

   paratively 
  slight 
  thickness 
  of 
  the 
  alluvium 
  of 
  the 
  Mississippi 
  

   valley. 
  He 
  says: 
  " 
  The 
  professor 
  [Hilgard] 
  therein 
  takes 
  the 
  

   view 
  that 
  the 
  alluvium 
  proper 
  beneath 
  New 
  Orleans 
  is 
  but 
  

   thirty-one 
  feet 
  thick, 
  arguing 
  that 
  the 
  marine 
  deposits 
  below 
  are 
  

   of 
  the 
  Port 
  Hudson 
  group. 
  I 
  followed 
  him 
  last 
  year 
  in 
  this 
  

   idea, 
  and 
  quoted 
  his 
  list 
  of 
  shells 
  under 
  the 
  head 
  of 
  the 
  Bluff 
  

   formation. 
  My 
  observations 
  this 
  season 
  oblige 
  me 
  to 
  modify 
  

   this 
  conclusion 
  somewhat. 
  Wishing 
  to 
  ascertain 
  as 
  accurately 
  

   as 
  possible 
  the 
  actual 
  depth 
  of 
  the 
  alluvium, 
  I 
  instituted 
  a 
  series 
  

   of 
  experiments 
  upon 
  the 
  water 
  of 
  wells 
  dug 
  in 
  the 
  Port 
  Hudson 
  

   formation 
  and 
  in 
  the 
  bottom 
  lands, 
  respectively. 
  I 
  have 
  found 
  

   (as 
  indeed, 
  Professor 
  Hilgard 
  had 
  told 
  me 
  that 
  he 
  should 
  expect) 
  

   that 
  the 
  former 
  contain 
  a 
  considerable 
  proportion 
  of 
  sulphates 
  

   and 
  carbonates, 
  while 
  the 
  latter 
  show 
  an 
  excess 
  of 
  chlorides. 
  

   This 
  result 
  is 
  uniform, 
  excepting 
  where 
  the 
  wells 
  happen 
  to 
  

   strike 
  considerable 
  beds 
  of 
  sand, 
  when 
  the 
  waters 
  are 
  too 
  pure 
  to 
  

   be 
  distinguished. 
  It 
  is 
  evident, 
  therefore, 
  that 
  by 
  testing 
  the 
  

   water 
  of 
  the 
  deepest 
  wells 
  dug 
  in 
  the 
  alluvium, 
  it 
  is 
  possible 
  to 
  

   tell 
  whether 
  they 
  pass 
  through 
  it 
  into 
  the 
  underlying 
  Port 
  

   Hudson 
  group 
  or 
  not. 
  The 
  patent 
  wells 
  that 
  are 
  made 
  by 
  

   simply 
  driving 
  a 
  tube 
  into 
  the 
  ground, 
  offer 
  great 
  facilities 
  for 
  

   this 
  research, 
  as 
  the 
  water 
  that 
  they 
  furnish 
  comes 
  necessarily 
  

  

  