﻿398 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  tively 
  low 
  the 
  output 
  of 
  cement 
  a 
  ton 
  of 
  coal 
  is 
  large, 
  the 
  yield 
  

   varying 
  from 
  50 
  to 
  120 
  barrels 
  a 
  ton 
  of 
  fuel. 
  The 
  Campbell 
  

   grate 
  used 
  by 
  the 
  Milwaukee 
  cement 
  co. 
  is 
  an 
  improvement 
  which 
  

   has 
  advantages 
  in 
  a 
  more 
  uniform 
  burning 
  of 
  the 
  clinker 
  and 
  in 
  

   a 
  considerable 
  economy 
  in 
  fuel. 
  This 
  grate 
  differs 
  in 
  design 
  but 
  

   is 
  similar 
  in 
  idea 
  to 
  a 
  grate 
  which 
  was 
  introduced 
  in 
  the 
  Lafarge 
  

   cement 
  works 
  in 
  France 
  some 
  years 
  ago. 
  

  

  The 
  burnt 
  rock 
  falling 
  from 
  the 
  bottom 
  of 
  the 
  kilns 
  is 
  gen- 
  

   erally 
  carefully 
  sorted 
  to 
  exclude 
  the 
  overburnt 
  and 
  the 
  under- 
  

   burnt 
  clinker 
  and 
  there 
  is 
  usually 
  a 
  mixing 
  of 
  material 
  from 
  

   different 
  beds 
  of 
  rock 
  to 
  produce 
  a 
  product 
  having 
  the 
  qualities 
  

   desired 
  in 
  the 
  finished 
  cement. 
  The 
  hard 
  burnt 
  clinker 
  being 
  

   excluded, 
  the 
  calcined 
  rock 
  is 
  soft 
  and 
  easily 
  reduced 
  to 
  powder. 
  

   The 
  lumps 
  are 
  first 
  broken 
  up 
  in 
  cast 
  iron 
  crushers, 
  and 
  are 
  then 
  

   ground 
  to 
  powder 
  in 
  millstones. 
  These 
  answer 
  the 
  purpose 
  very 
  

   satisfactorily 
  and 
  economically 
  for 
  natural 
  cement 
  and 
  are 
  gen- 
  

   erally 
  preferred 
  to 
  more 
  modern 
  mills. 
  It 
  is 
  a 
  recent 
  practice 
  

   to 
  pass 
  the 
  material 
  over 
  a 
  separator 
  after 
  it 
  has 
  been 
  cracked 
  so 
  

   as 
  to 
  take 
  .out 
  the 
  material 
  which 
  has 
  been 
  already 
  powdered 
  

   and 
  thus 
  relieve 
  the 
  work 
  on 
  the 
  mills. 
  

  

  In 
  the 
  natural 
  cement 
  trade 
  there 
  are 
  several 
  standards 
  of 
  

   weight 
  a 
  barrel, 
  as 
  follows: 
  Rosendale, 
  300 
  lb. 
  net; 
  Pennsyl- 
  

   vania, 
  280 
  lb. 
  net 
  in 
  barrels, 
  300 
  lb. 
  net 
  in 
  sacks; 
  western 
  stand- 
  

   ard, 
  265 
  lb. 
  net. 
  

  

  In 
  regard 
  to 
  quality 
  of 
  the 
  cement 
  there 
  are 
  very 
  considerable 
  

   variations 
  in 
  the 
  new 
  materials 
  and 
  it 
  is 
  rather 
  difficult 
  to 
  adopt 
  

   any 
  criterion. 
  Cements 
  of 
  the 
  Rosendale 
  district 
  will 
  ordinarily 
  

   show 
  a 
  tensile 
  strength 
  of 
  70 
  lb. 
  at 
  one 
  day 
  neat, 
  and 
  95$ 
  

   of 
  the 
  raw 
  material 
  will 
  pass 
  the 
  no. 
  50 
  sieve. 
  This 
  a 
  very 
  fair 
  

   standard 
  of 
  quality 
  for 
  natural 
  cements. 
  In 
  the 
  Lehigh 
  valley 
  

   district 
  of 
  Pennsylvania 
  the 
  manufacturers 
  are 
  making^ 
  a 
  grade 
  

   of 
  natural 
  cement 
  which 
  they 
  style 
  " 
  improved 
  " 
  cement, 
  and 
  

   which 
  is 
  made 
  from 
  a 
  mixture 
  of 
  natural 
  cement 
  with 
  a 
  percent- 
  

   age 
  of 
  the 
  product 
  of 
  portland 
  cement 
  kilns. 
  This 
  cement 
  

   shows 
  higher 
  tensile 
  strength 
  than 
  the 
  rock 
  cement 
  and 
  com- 
  

   mands 
  a 
  rather 
  better 
  price. 
  >, 
  .. 
  

  

  