﻿272 
  Geological 
  Survey 
  of 
  Louisiana 
  Sect. 
  

  

  show 
  the 
  same 
  degree 
  of 
  plasticity 
  as 
  clay, 
  for 
  a 
  shale 
  is 
  nothing 
  

   more 
  than 
  a 
  clay 
  which 
  has 
  become 
  consolidated 
  by 
  simple 
  pres- 
  

   sure 
  of 
  the 
  overlying 
  sediments 
  that 
  cover 
  it. 
  The 
  practical 
  

   bearing 
  of 
  slaking 
  is 
  twofold. 
  It 
  comes 
  into 
  play 
  when 
  the 
  clay 
  

   is 
  being 
  mixed 
  with 
  water 
  before 
  molding, 
  when 
  it 
  is 
  desired 
  that 
  

   the 
  clay 
  shall 
  permit 
  the 
  tempering 
  water 
  to 
  enter 
  all 
  of 
  its 
  pores 
  

   both 
  thoroughly 
  and 
  quickly. 
  It 
  also 
  comes 
  into 
  play 
  when 
  

   clays 
  are 
  being 
  washed 
  in 
  order 
  to 
  free 
  them 
  from 
  any 
  coarse 
  

   particles 
  of 
  sand 
  that 
  they 
  may 
  contain, 
  in 
  which 
  case 
  if 
  the 
  

   clay 
  slakes 
  rapidly, 
  the 
  operation 
  of 
  washing 
  can 
  be 
  carried 
  on 
  

   with 
  greater 
  speed 
  and 
  at 
  the 
  same 
  time 
  the 
  result 
  will 
  be 
  more 
  

  

  complete. 
  

  

  Physical 
  Tests 
  of 
  Louisiana 
  Samples 
  

  

  148. 
  (Survey 
  No. 
  53.) 
  Alluvial 
  clay 
  R. 
  R. 
  track 
  just 
  S. 
  of 
  

  

  Little 
  R. 
  

  

  This 
  was 
  a 
  somewhat 
  gritty 
  clay, 
  and 
  slaked 
  easily 
  when 
  

   thrown 
  into 
  water. 
  On 
  working 
  it 
  up 
  it 
  developed 
  very 
  good 
  

   plasticity, 
  and 
  required 
  only 
  20 
  per 
  cent, 
  of 
  water 
  to 
  mix 
  it, 
  

   which 
  is 
  low. 
  The 
  tensile 
  strength 
  of 
  air 
  dried 
  briquettes 
  made 
  

   from 
  this 
  mass 
  is 
  55 
  lbs. 
  

  

  The 
  ratio 
  of 
  fine 
  to 
  coarse 
  particles 
  is 
  shown 
  by 
  the 
  mechani- 
  

   cal 
  analysis 
  which 
  gave 
  

  

  Clay 
  and 
  fine 
  silt 
  73 
  per 
  cent. 
  

  

  Fine 
  sand 
  27 
  

  

  The 
  bricklets 
  made 
  from 
  the 
  clay 
  had 
  an 
  air 
  shrinkage 
  of 
  

   6 
  per 
  cent. 
  

  

  At 
  cone 
  3 
  the 
  total 
  shrinkage 
  was 
  7>^ 
  per 
  cent., 
  and 
  incipient 
  

   fusion 
  had 
  begun. 
  At 
  this 
  temperature 
  the 
  clay 
  burned 
  to 
  a 
  

   good 
  red 
  color. 
  It 
  contains 
  small 
  specks 
  of 
  pyrite 
  which 
  pro- 
  

   duce 
  little 
  fused 
  spots 
  when 
  the 
  clay 
  is 
  burned. 
  

  

  At 
  cone 
  5 
  the 
  shrinkage 
  is 
  the 
  same 
  and 
  vitrifaction 
  began 
  at 
  9. 
  

  

  The 
  clay 
  is 
  not 
  to 
  be 
  classed 
  as 
  a 
  fire 
  clay 
  for 
  it 
  is 
  thoroughly 
  

   viscous 
  at 
  cone 
  26. 
  

  

  It 
  would 
  no 
  doubt 
  work 
  for 
  the 
  manufacture 
  of 
  a 
  good 
  grade 
  

   of 
  brick, 
  and 
  would 
  perhaps 
  lend 
  itself 
  to 
  the 
  molding 
  of 
  pressed 
  

   brick 
  by 
  the 
  dry-press 
  process. 
  

  

  149. 
  (Survey 
  No. 
  40.) 
  

  

  This 
  is 
  also 
  coarse 
  grained 
  sandy 
  clay 
  and 
  at 
  the 
  same 
  time 
  

   one 
  that 
  slakes 
  very 
  rapidly. 
  

  

  