﻿CLAYS 
  OF 
  I^EW 
  YORK 
  561 
  

  

  Orange 
  2102° 
  F. 
  

  

  White 
  2372° 
  F. 
  

  

  Dazzling 
  white 
  2732° 
  F. 
  

  

  Mechanical 
  analysis 
  of 
  clays 
  

  

  The 
  mechanical 
  analysis 
  of 
  a 
  clay 
  determines 
  the 
  percentage 
  of 
  

   particles 
  of 
  different 
  sizes 
  which 
  it 
  contains. 
  

  

  The 
  method 
  employed 
  for 
  this 
  determination 
  is 
  partly 
  a 
  dry 
  and 
  

   partly 
  a 
  wet 
  one. 
  Clays 
  which 
  are 
  used 
  for 
  the 
  finer 
  grades 
  of 
  

   ware 
  have 
  to 
  be 
  sufficiently 
  fine 
  to 
  pass 
  through 
  a 
  150 
  mesh 
  sieve. 
  

   The 
  relative 
  quantity 
  of 
  coarser 
  particles 
  which 
  a 
  clay 
  contains 
  

   can 
  be 
  found 
  out 
  by 
  sieving. 
  

  

  If 
  the 
  clay 
  grains 
  are 
  smaller 
  than 
  ^-J-^- 
  of 
  an 
  inch, 
  the 
  com- 
  

   mon 
  metiiod 
  of 
  sorting 
  them 
  is 
  by 
  means 
  of 
  a 
  rising 
  current 
  of 
  

   water. 
  This 
  operation 
  is 
  known 
  as 
  " 
  slumming 
  " 
  and 
  consists 
  in 
  

   brief 
  of 
  placing 
  a 
  known 
  weight 
  of 
  clay 
  in 
  a 
  vertical 
  tube 
  through 
  

   which 
  a 
  current 
  of 
  water 
  passes. 
  The 
  velocity 
  of 
  the 
  current 
  can 
  be 
  

   regulated. 
  Careful 
  experiment 
  has 
  determined 
  the 
  size 
  of 
  par- 
  

   ticles 
  that 
  are 
  carried 
  off 
  by 
  a 
  given 
  velocity 
  of 
  the 
  current. 
  The 
  

   water 
  as 
  it 
  passes 
  o& 
  at 
  the 
  top 
  of 
  the 
  tube 
  is 
  conducted 
  into 
  jars, 
  

   where 
  the 
  suspended 
  particles 
  are 
  allowed 
  to 
  settle, 
  and 
  can 
  after- 
  

   wards 
  be 
  collected 
  and 
  weighed. 
  

  

  The 
  diameters 
  of 
  the 
  grains 
  commonly 
  separated 
  are:' 
  

  

  Clay 
  substance 
  ,. 
  . 
  . 
  Up 
  to 
  . 
  01 
  mm 
  

  

  Silt 
  01 
  —.025 
  mm 
  

  

  Finest 
  sand 
  . 
  . 
  025 
  — 
  . 
  04 
  mm 
  

  

  Fine 
  sand 
  04 
  — 
  .2 
  mm 
  

  

  An 
  excess 
  of 
  the 
  finest 
  particles 
  tends 
  to 
  increase 
  the 
  shrinkage 
  of 
  

   the 
  clay, 
  while 
  the 
  coarser 
  particles 
  have 
  the 
  reverse 
  effect. 
  For 
  

   thorough 
  comparative 
  work 
  on 
  the 
  physical 
  properties 
  of 
  clay, 
  it 
  is 
  

   well 
  to 
  make 
  a 
  mechanical 
  analysis. 
  This 
  has 
  been 
  done 
  with 
  a 
  

   number 
  of 
  the 
  'New 
  York 
  samples. 
  

  

  Chemical 
  effects 
  of 
  heating. 
  On 
  heating 
  a 
  clay 
  to 
  redness, 
  it 
  

   undergoes 
  certain 
  changes, 
  which 
  exert 
  an 
  influence 
  on 
  the 
  physical 
  

  

  