﻿I] 
  Historical 
  Review 
  : 
  Second 
  Period 
  27 
  

  

  the 
  State 
  in 
  a 
  northerl}^ 
  and 
  northwesterly 
  direction 
  and 
  on 
  either 
  

   side 
  there 
  is 
  a 
  dipping 
  of 
  the 
  strata 
  away 
  from 
  the 
  axis 
  toward 
  

   the 
  Mississippi 
  on 
  the 
  east 
  side 
  and 
  westerly 
  or 
  southwesterly 
  on 
  

   the 
  west 
  side. 
  The 
  " 
  Northern 
  Lignitic 
  " 
  is 
  correlated 
  with 
  the 
  

   Buhrstone 
  of 
  the 
  states 
  east 
  of 
  the 
  Mississippi 
  (p. 
  394). 
  He 
  is 
  

   led 
  to 
  make 
  this 
  mistake 
  on 
  account 
  of 
  supposing 
  that 
  the 
  now 
  

   well 
  known 
  Midway 
  Eocene 
  beds 
  in 
  west 
  Tenuesee 
  lying 
  immedi- 
  

   ately 
  upon 
  the 
  Cretaceous, 
  were 
  of 
  Lower 
  Claiborne 
  age. 
  Hence 
  

   the 
  intervening 
  Lignitic 
  beds 
  should 
  probably 
  be 
  of 
  the 
  same 
  

   age. 
  The 
  Cretaceous 
  backbone 
  is 
  held 
  responsible 
  for 
  causing 
  

   the 
  extremely 
  lignitic 
  character 
  of 
  the 
  formations 
  of 
  north 
  

   Louisiana 
  (p. 
  396). 
  The 
  barrenness 
  of 
  the 
  Grand 
  Gulf 
  beds 
  is 
  

   attributed 
  to 
  some 
  exclusion 
  of 
  the 
  waters 
  in 
  which 
  they 
  were 
  

   being 
  deposited 
  from 
  the 
  sea 
  (p. 
  348). 
  The 
  calcareous 
  concre- 
  

   tions 
  found 
  near 
  the 
  base 
  of 
  this 
  formation 
  may 
  have 
  been 
  

   derived 
  from 
  organic 
  remains. 
  The 
  Port 
  Hudson 
  beds 
  underlie 
  

   the 
  Mississippi 
  alluvium 
  up 
  as 
  far 
  as 
  Memphis, 
  and 
  the 
  Red 
  river 
  

   as 
  far 
  as 
  Shreveport 
  (p. 
  401). 
  

  

  The 
  Smithsonian 
  memoir 
  by 
  Hilgard 
  on 
  the 
  ' 
  'Geology 
  of 
  Lower 
  

   Louisiana 
  and 
  the 
  Rock 
  salt 
  of 
  Petite 
  Anse* 
  published 
  in 
  1872 
  

   is 
  a 
  more 
  complete 
  statement 
  of 
  the 
  first 
  article 
  on 
  the 
  subject 
  pub- 
  

   lished 
  in 
  the 
  American 
  Journal 
  of 
  Science 
  in 
  1869. 
  He 
  describes 
  

   the 
  Port 
  Hudson 
  section 
  and 
  gives 
  a 
  detailed 
  description 
  of 
  each 
  

   of 
  the 
  Five 
  Islands. 
  In 
  this 
  article 
  he 
  takes 
  the 
  view 
  that 
  the 
  Five 
  

   Islands 
  are 
  but 
  the 
  erosion-formed 
  outliers 
  of 
  a 
  Cretaceous 
  ridge 
  

   or 
  backbone 
  which 
  traverses 
  Louisiana 
  from 
  the 
  northwest 
  cor- 
  

   ner 
  in 
  the 
  direction 
  of 
  Vermillion 
  bay 
  ; 
  the 
  salt 
  being 
  of 
  Creta- 
  

   ceous 
  rather 
  than 
  early 
  Quaternary 
  age. 
  He 
  thinks 
  that 
  at 
  the 
  

   beginning 
  of 
  Tertiary 
  time 
  the 
  existence 
  of 
  the 
  axis 
  of 
  elevation 
  

   was 
  marked 
  merely 
  by 
  a 
  number 
  of 
  disconnected 
  islands. 
  In 
  

   later 
  geological 
  time 
  the 
  lower 
  five 
  outcrops 
  were 
  buried 
  under 
  

   deposits 
  of 
  Orange 
  Sand 
  and 
  Port 
  Hudson 
  material, 
  as 
  indeed 
  

   was 
  the 
  whole 
  Mississippi 
  valley, 
  and 
  in 
  the 
  re-excavation 
  of 
  

   the 
  valley 
  by 
  the 
  Mississippi 
  river 
  the 
  material 
  covering 
  the 
  

   Cretaceous 
  nuceli 
  was 
  not 
  eroded 
  so 
  much 
  as 
  the 
  surrounding 
  

   country, 
  thus 
  forming 
  the 
  islands. 
  

  

  *Smitli. 
  Contributions, 
  vol. 
  23, 
  No. 
  248, 
  32 
  pp. 
  

  

  