﻿178 
  GeoIvOGical 
  Survey 
  of 
  Louisiana 
  Sect.] 
  

  

  the 
  Cottonwood 
  ; 
  but 
  ash, 
  hickory, 
  red 
  oak 
  and 
  sweet 
  gum 
  also 
  

   occur. 
  

  

  As 
  the 
  distance 
  from 
  the 
  river 
  and 
  bayous 
  increases 
  the 
  amount 
  

   of 
  sand 
  in 
  the 
  soil 
  decreases 
  and 
  at 
  a 
  short 
  distance 
  from 
  the 
  

   stream 
  channels 
  the 
  sandy 
  front 
  land 
  has 
  changed 
  into 
  stiff 
  clay 
  

   back 
  land. 
  This 
  ranges 
  in 
  color 
  from 
  a 
  dirty 
  cherry-red 
  to 
  a 
  

   rich 
  dark 
  mahogany. 
  Here 
  the 
  cypress 
  and 
  hackberry 
  find 
  con- 
  

   genial 
  homes. 
  

  

  The 
  surface 
  aspect 
  of 
  the 
  little 
  spots 
  of 
  prairie 
  land 
  scattered 
  

   through 
  the 
  bottom 
  is 
  markedly 
  different 
  from 
  that 
  of 
  the 
  sur- 
  

   rounding 
  heavily 
  wooded 
  country. 
  There 
  are 
  a 
  few 
  scattered 
  

   cottonwoods, 
  numerous 
  scrub 
  thorns 
  (hawthorn 
  and 
  honey-locust) 
  

   and 
  grass 
  ; 
  altogether 
  a 
  sort 
  of 
  forbidding 
  looking 
  place, 
  but 
  

   when 
  cleared 
  yielding 
  excellent 
  crops. 
  If 
  the 
  soil 
  is 
  in 
  any 
  way 
  

   washed 
  off, 
  leaving 
  the 
  underlying 
  red 
  and 
  yellow 
  clayey 
  sand, 
  

   the 
  fertility 
  of 
  the 
  field 
  is 
  a 
  thing 
  of 
  the 
  past. 
  

  

  Origiii. 
  — 
  It 
  is 
  easy 
  to 
  see 
  the 
  manner 
  in 
  which 
  the 
  front 
  and 
  

   back 
  land 
  have 
  been 
  formed. 
  Indeed 
  it 
  has 
  been 
  so 
  often 
  stated 
  

   and 
  is 
  so 
  well 
  understood 
  that 
  a 
  very 
  brief 
  statement 
  will 
  suffice 
  

   here. 
  When 
  the 
  water 
  flows 
  over 
  the 
  banks 
  in 
  time 
  of 
  high 
  water 
  

   its 
  velocity 
  is 
  greatly 
  checked 
  and 
  it 
  deposits 
  its 
  heavier 
  sandy 
  

   material 
  on 
  the 
  immediate 
  banks 
  of 
  the 
  stream 
  ; 
  thus 
  forming 
  

   the 
  sandy 
  front 
  land. 
  The 
  waters 
  which 
  now 
  contains 
  only 
  the 
  

   finest 
  sediment 
  passes 
  into 
  the 
  lower 
  parts 
  of 
  the 
  bottoms, 
  form- 
  

   ing 
  great 
  temporary 
  lakes. 
  Having 
  little 
  or 
  no 
  velocity, 
  the 
  

   water 
  is 
  unable 
  to 
  keep 
  even 
  this 
  very 
  fine 
  sediment 
  in 
  suspen- 
  

   sion. 
  This 
  is 
  gradually 
  deposited, 
  forming 
  a 
  stiff 
  claj\ 
  

  

  In 
  times 
  of 
  high 
  floods 
  the 
  sedimentation 
  is 
  very 
  large. 
  Large 
  

   areas 
  of 
  stiff 
  back 
  sand 
  are 
  often 
  sanded. 
  Thus, 
  in 
  the 
  flood 
  of 
  

   1892 
  Cottonwood 
  bayou 
  covered 
  a 
  large 
  area 
  of 
  stiff 
  land 
  lying 
  

   along 
  its 
  banks 
  with 
  sandy 
  material. 
  It 
  is 
  stated 
  that 
  in 
  places 
  

   this 
  deposit 
  amounted 
  to 
  two 
  or 
  three 
  feet. 
  

  

  The 
  formation 
  of 
  the 
  prairie 
  land 
  can 
  only 
  be 
  a 
  matter 
  of 
  con- 
  

   jecture. 
  The 
  Eocene 
  Tertiary 
  of 
  northern 
  Louisiana 
  abounds 
  in 
  

   little 
  bare 
  spots 
  caused 
  by 
  the 
  outcropping 
  of 
  unusually 
  calca- 
  

   reous 
  beds. 
  It 
  may 
  be 
  that 
  certain 
  layers 
  of 
  the 
  older 
  beds 
  in 
  the 
  

   bottoms 
  contain 
  a 
  large 
  amount 
  of 
  calcareous 
  matter 
  and 
  are 
  

   responsible 
  for 
  the 
  formation 
  of 
  these 
  spots. 
  The 
  section 
  given 
  

   above 
  (p. 
  175) 
  shows 
  quite 
  a 
  calcareous 
  layer. 
  

  

  