﻿II] 
  Special 
  Report 
  No. 
  4 
  : 
  Clays 
  273 
  

  

  It 
  took 
  21 
  per 
  cent, 
  of 
  water 
  to 
  work 
  it 
  up 
  and 
  the 
  air 
  shrink- 
  

  

  ge 
  of 
  the 
  bricklets 
  made 
  from 
  this 
  mass 
  was 
  10 
  per 
  cent. 
  

  

  The 
  mechanical 
  composition 
  is 
  very 
  similar 
  to 
  the 
  preceding 
  

  

  one 
  and 
  is 
  : 
  

  

  Clay 
  and 
  fine 
  silt 
  73-50 
  per 
  cent 
  

  

  Very 
  fine 
  sand 
  , 
  26.30 
  " 
  

  

  99.80 
  

  

  The 
  tensile 
  strength 
  was 
  45 
  lbs. 
  per 
  sq. 
  in. 
  which 
  is 
  sufficient 
  

   for 
  a 
  brick 
  clay, 
  but 
  really 
  should 
  be 
  greater. 
  

  

  At 
  cone 
  3 
  the 
  clay 
  burns 
  light 
  red 
  and 
  shows 
  signs 
  of 
  

   incipient 
  fusion. 
  

  

  At 
  cone 
  5 
  the 
  total 
  shrinkage 
  was 
  13 
  per 
  cent, 
  and 
  the 
  color 
  

   of 
  the 
  bricklet 
  had 
  changed 
  to 
  a 
  deep 
  red, 
  while 
  the 
  iron 
  oxide 
  

   mixed 
  in 
  with 
  the 
  clay 
  substance 
  had 
  caused 
  the 
  latter 
  to 
  sinter, 
  

   but 
  the 
  brick 
  was 
  by 
  no 
  means 
  vitrified. 
  

  

  In 
  burning 
  it 
  would 
  be 
  best 
  not 
  to 
  raise 
  the 
  temperature 
  above 
  

   cone 
  3, 
  for 
  it 
  destroys 
  the 
  color 
  and 
  also 
  the 
  texture 
  of 
  the 
  body. 
  

  

  The 
  clay 
  contained 
  but 
  a 
  trace 
  of 
  soluble 
  salts 
  and 
  therefore 
  

  

  there 
  would 
  be 
  but 
  little 
  danger 
  of 
  its 
  becoming 
  covered 
  with 
  a 
  

  

  coating 
  unless 
  it 
  were 
  from 
  the 
  mortar 
  after 
  being 
  set 
  in 
  the 
  wall. 
  

  

  150. 
  (Survey 
  No. 
  62.) 
  Carter's 
  pottery 
  works, 
  2^ 
  mi. 
  E. 
  of 
  

  

  Robeline, 
  La. 
  

  

  This 
  is 
  quite 
  a 
  plastic 
  clay 
  and 
  one 
  of 
  the 
  best 
  of 
  the 
  lot 
  sub- 
  

   mitted. 
  As 
  the 
  tensile 
  strength 
  often 
  stands 
  in 
  more 
  or 
  less 
  

   direct 
  relation 
  to 
  the 
  plasticity, 
  it 
  may 
  be 
  remarked 
  that 
  the 
  

   latter 
  is 
  75 
  lbs. 
  per 
  sq. 
  in. 
  

  

  The 
  mechanical 
  analysis 
  also 
  indicates 
  that 
  the 
  clay 
  has 
  mostly 
  

   plastic 
  particles, 
  for 
  it 
  gave 
  

  

  Fine 
  sand 
  None 
  

  

  Fine 
  silt 
  80.75 
  per 
  cent 
  

  

  Clay 
  20. 
  20 
  " 
  

  

  100.95 
  

  

  At 
  cone 
  i 
  the 
  clay 
  burns 
  hard 
  and 
  dense 
  with 
  a 
  total 
  shrink- 
  

   age 
  of 
  13 
  per 
  cent. 
  

  

  At 
  cone 
  3 
  the 
  shrinkage 
  was 
  the 
  same, 
  but 
  vitrification 
  had 
  

   begun. 
  

  

  At 
  cone 
  5 
  the 
  clay 
  began 
  to 
  get 
  viscous. 
  

  

  This 
  would 
  bar 
  it 
  out 
  from 
  being 
  a 
  fireclay. 
  It 
  burns 
  however 
  

  

  R 
  

  

  