﻿658 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  particularly 
  to 
  tlie 
  production 
  of 
  such 
  materials 
  as 
  exhibit 
  coarse 
  

   article 
  and 
  fine 
  grains, 
  sucli 
  as 
  gTOgs 
  for 
  instance. 
  

  

  Tlie 
  material 
  to 
  he 
  ground 
  in 
  ball 
  mills 
  must 
  be 
  air-dried 
  and 
  

   only 
  in 
  those 
  of 
  the 
  intermittent 
  t}^e 
  can 
  damp 
  or 
  wet 
  material 
  

   be 
  introduced. 
  This 
  is 
  necessary, 
  for 
  instance, 
  in 
  the 
  case 
  of 
  

   glazes. 
  If 
  the 
  material 
  to 
  be 
  ground 
  must 
  be 
  kept 
  from 
  contaci 
  

   with 
  iron, 
  the 
  interior 
  of 
  the 
  cylinder 
  is 
  lined 
  ^rith 
  porcelain, 
  and 
  

   instead 
  of 
  iron 
  balls 
  porcelain 
  or 
  flint 
  ones 
  are 
  used. 
  The 
  capacity 
  

   of 
  ball 
  mills 
  is 
  highly 
  variable, 
  depending 
  on 
  the 
  fineness 
  of 
  the 
  

   product 
  desired, 
  the 
  hardness 
  of 
  the 
  material 
  to 
  be 
  ground, 
  and 
  also 
  

   on 
  the 
  size 
  of 
  the 
  mill, 
  therefore 
  the 
  hourly 
  production 
  Avill 
  vary 
  

   in 
  the 
  case 
  of 
  gTog 
  between 
  1500 
  and 
  3000 
  pounds. 
  In 
  this 
  case, 
  

   for 
  every 
  2000 
  pounds 
  ground 
  in 
  an 
  hour, 
  three 
  to 
  10 
  horse 
  power 
  

  

  is 
  required. 
  

  

  Wet 
  methods 
  of 
  preparation 
  

  

  The 
  clay 
  can 
  commonly 
  be 
  tempered 
  directly 
  as 
  it 
  comes 
  from 
  

   the 
  bank 
  instead 
  of 
  being 
  pulverized, 
  which 
  is 
  always 
  necessary 
  

   in 
  the 
  case 
  of 
  shales. 
  

  

  The 
  wet 
  methods 
  employed 
  are: 
  

  

  8oalc 
  pits. 
  These 
  are 
  the 
  most 
  primitive 
  contrivances 
  at 
  present 
  

   used 
  for 
  the 
  preparation 
  of 
  clays. 
  There 
  is 
  a 
  rectangular 
  pit 
  about 
  

   5 
  feet 
  deep 
  and 
  6 
  feet 
  square. 
  The 
  Long 
  Island 
  pits 
  are 
  usually 
  

   rectangular 
  in 
  shape. 
  Into 
  this 
  the 
  clay 
  and 
  sand 
  are 
  dumped, 
  

   water 
  poured 
  on 
  and 
  the 
  mass 
  allowed 
  to 
  soak 
  over 
  night, 
  so 
  as 
  

   thoroughly 
  to 
  soften 
  it. 
  The 
  following 
  morning 
  the 
  softened 
  ma- 
  

   terial 
  is 
  shoveled 
  into 
  the 
  machine. 
  Two 
  men 
  — 
  pit 
  shovelers 
  — 
  

   do 
  this, 
  and 
  it 
  is 
  highly 
  important 
  that 
  they 
  be 
  men 
  of 
  intelligence 
  

   and 
  attend 
  to 
  their 
  work, 
  seeing 
  that 
  the 
  right 
  proportions 
  of 
  clay 
  

   and 
  sand 
  are 
  shoveled 
  into 
  the 
  machine. 
  From 
  one 
  tJiird 
  to 
  one 
  

   quarter 
  is 
  the 
  amount 
  of 
  sand 
  added. 
  The 
  operation 
  of 
  mixing 
  the 
  

   clay 
  and 
  sand 
  is 
  called 
  tempering; 
  the 
  addition 
  of 
  sand 
  is 
  in 
  most 
  

   cases 
  not 
  necessary, 
  as 
  the 
  majority 
  of 
  clays 
  have 
  sufficient 
  of 
  it 
  

   naturally. 
  The 
  object 
  of 
  the 
  addition 
  of 
  sand 
  is 
  to 
  counteract 
  the 
  

   effect 
  of 
  the 
  alumina, 
  by 
  preventing 
  a 
  too 
  great 
  and 
  uneven 
  shrink- 
  

  

  