﻿GEOLOGY. 
  255 
  

  

  of 
  considerable 
  volume, 
  issuing 
  not 
  much 
  above 
  the 
  low- 
  

   water 
  level 
  of 
  the 
  Mississippi, 
  and 
  washing 
  out 
  the 
  beds 
  

   of 
  sand, 
  through 
  which 
  they 
  flow, 
  have 
  produced 
  con- 
  

   siderable 
  basin-like 
  subsidences, 
  and 
  occasioned 
  a 
  peculiar 
  

   indented 
  configuration 
  of 
  the 
  bluff 
  margin, 
  such 
  as 
  a 
  

   striking 
  example 
  is 
  afforded 
  of 
  in 
  the 
  imnch-hoivh 
  just 
  

   above 
  Natchez. 
  

  

  Where 
  the 
  tertiary 
  strata 
  are 
  exposed, 
  or 
  approach 
  

   near 
  the 
  surface, 
  as 
  in 
  portions 
  of 
  Hinds, 
  Madison, 
  and 
  

   other 
  middle 
  counties, 
  springs, 
  at 
  least 
  such 
  as 
  are 
  

   constant, 
  are 
  almost 
  entirely 
  absent 
  ; 
  but 
  well-water 
  is 
  

   frequently 
  obtained 
  from 
  twenty 
  to 
  thirty-five 
  feet 
  below 
  

   the 
  surface. 
  If 
  obtained 
  at 
  the 
  greater 
  depth 
  of 
  fifty 
  to 
  

   eighty 
  feet, 
  it 
  is 
  generally 
  fetid 
  and 
  unfit 
  for 
  use, 
  being 
  

   derived 
  from 
  the 
  black 
  offensive 
  muck 
  of 
  the 
  tertiary 
  

   strata. 
  

  

  The 
  shallow 
  wells 
  in 
  use, 
  are 
  rarely 
  permanent, 
  

   seldom 
  lasting 
  more 
  than 
  a 
  few 
  years, 
  when 
  others 
  are 
  

   dug 
  in 
  situations 
  previously 
  experimented 
  on 
  with 
  the 
  

   auger. 
  

  

  The 
  water 
  is 
  evidently 
  derived 
  from 
  the 
  surface, 
  per- 
  

   colating 
  through 
  the 
  upper 
  strata 
  to 
  the 
  pipe-clay 
  and 
  

   sand, 
  which 
  gives 
  it, 
  frequently, 
  a 
  somewhat 
  turbid 
  or 
  

   milky 
  appearance. 
  An 
  instance 
  occurred, 
  in 
  the 
  south- 
  

   ern 
  part 
  of 
  Hinds, 
  where 
  a 
  fair 
  quality 
  of 
  water 
  was 
  

   abundantly 
  obtained 
  at 
  fifteen 
  feet, 
  within 
  a 
  few 
  yards 
  

   of 
  the 
  spot 
  where 
  a 
  well 
  had 
  been 
  recently 
  sunk 
  eighty 
  

   feet 
  to 
  the 
  black 
  mud, 
  and 
  consequently 
  abandoned. 
  

  

  This 
  black, 
  fetid 
  muck 
  of 
  the 
  prairies, 
  seems 
  exten- 
  

   sively 
  dispersed, 
  and 
  has 
  been 
  encountered 
  at 
  various 
  

   localities, 
  from 
  the 
  vicinity 
  of 
  Oxford 
  to 
  that 
  of 
  Bran- 
  

   don, 
  at 
  a 
  depth 
  of 
  from 
  fifty 
  to 
  eighty 
  feet 
  — 
  a 
  difference 
  

   not 
  greater, 
  perhaps, 
  than 
  that 
  of 
  the 
  inequalities 
  of 
  the 
  

  

  