﻿LIMESTONES 
  OP 
  NEW 
  YORK 
  AND 
  THEIR 
  ECONOMIC 
  VALUE 
  425 
  

  

  lb. 
  a 
  minute); 
  6) 
  normal 
  pat 
  tests 
  for 
  constancy 
  of 
  volume; 
  7) 
  the 
  

   proportioning 
  of 
  test 
  mortars 
  (cement, 
  water 
  and 
  sand) 
  by 
  weight. 
  

  

  By 
  fixing 
  standards 
  in 
  these 
  important 
  respects 
  the 
  committee 
  

   has 
  rendered 
  a 
  very 
  great 
  service 
  to 
  this 
  field 
  of 
  investigation. 
  

   The 
  only 
  tool 
  suggested 
  by 
  this 
  committee 
  for 
  manipulating 
  

   mortars 
  was 
  the 
  trowel. 
  At 
  first 
  very 
  great 
  differences 
  in 
  results 
  

   were 
  obtained 
  by 
  different 
  operators 
  manipulating 
  mortars 
  in 
  

   this 
  way. 
  In 
  recent 
  years 
  however, 
  as 
  good 
  laboratories 
  and 
  

   skilled 
  operators 
  have 
  become 
  more 
  numerous, 
  there 
  has 
  been 
  a 
  

   great 
  improvement 
  in 
  this 
  respect 
  and 
  fairly 
  comparable 
  results 
  

   are 
  obtained. 
  It 
  is 
  an 
  open 
  question 
  whether 
  a 
  change 
  to 
  the 
  

   foreign 
  practice 
  of 
  employing 
  mechanical 
  hammers 
  would 
  now 
  

   afford 
  any 
  improvement. 
  A 
  new 
  committee 
  of 
  the 
  society 
  is 
  at 
  

   present 
  considering 
  methods 
  with 
  a 
  view 
  to 
  revising 
  the 
  old 
  re- 
  

   port 
  and 
  extending 
  its 
  scope. 
  

  

  In 
  specifications, 
  test 
  requirements 
  are 
  usually 
  fixed 
  as 
  follows: 
  

  

  For 
  natural 
  cements: 
  fineness, 
  normal 
  pat 
  tests, 
  tensile 
  

   strength 
  one 
  day 
  neat, 
  tensile 
  strength 
  seven 
  days 
  neat, 
  tensile 
  

   strength 
  seven 
  days, 
  one 
  to 
  two 
  standard 
  sand. 
  

  

  For 
  portland 
  cements: 
  fineness, 
  setting-time, 
  normal 
  pat 
  

   tests, 
  tensile 
  strength 
  at 
  seven 
  days, 
  one 
  to 
  three 
  standard 
  sand. 
  

  

  A 
  weight 
  to 
  a 
  unit 
  of 
  volume 
  is 
  not 
  used, 
  the 
  specific 
  gravity 
  

   determination 
  being 
  substituted 
  for 
  it 
  to 
  great 
  advantage. 
  There 
  

   is 
  a 
  very 
  frequent 
  use 
  of 
  the 
  boiling 
  test 
  in 
  some 
  form 
  or 
  other. 
  

   Many 
  of 
  the 
  specifications 
  for 
  this, 
  test 
  are 
  very 
  badly 
  considered 
  

   and 
  illogical. 
  As 
  Dr 
  Michaelis 
  originated 
  this 
  test 
  it 
  may 
  not 
  be 
  

   amiss 
  to 
  state 
  what 
  the 
  boiling 
  test 
  is 
  as 
  Michaelis 
  makes 
  it, 
  to 
  wit: 
  

   A 
  thin 
  pan 
  of 
  neat 
  cement 
  three 
  inches 
  in 
  diameter, 
  one 
  half 
  inch 
  

   thick 
  at 
  the 
  center 
  and 
  drawn 
  to 
  a 
  thin 
  edge 
  at 
  the 
  circumference, 
  

   is 
  prepared 
  on 
  a 
  piece 
  of 
  moist 
  filter 
  paper 
  set 
  on 
  a 
  glass 
  plate. 
  

   After 
  setting 
  the 
  cake 
  is 
  removed 
  from 
  the 
  filter 
  paper 
  and 
  placed 
  

   under 
  cover 
  in 
  a 
  damp 
  atmosphere 
  to 
  protect 
  it 
  from 
  surface 
  

   drj 
  ing 
  for 
  24 
  hours, 
  at 
  the 
  end 
  of 
  which 
  time 
  the 
  cake 
  is 
  put 
  in 
  a 
  

   covered 
  bath 
  of 
  cold 
  water. 
  This 
  bath 
  is 
  then 
  heated 
  to 
  the 
  boil- 
  

   ing 
  point 
  and 
  is 
  maintained 
  boiling 
  for 
  three 
  hours. 
  The 
  pat 
  is 
  

   then 
  taken 
  out 
  and 
  its 
  condition 
  recorded. 
  

  

  