﻿LIMESTONES 
  OF 
  NEW 
  YORK 
  AND 
  THEIR 
  ECONOMIC 
  VALUE 
  411 
  

  

  sight 
  preferable 
  to 
  the 
  method 
  described 
  above 
  but 
  the 
  complete 
  

   displacement 
  of 
  the 
  air 
  entangled 
  in 
  the 
  cement 
  is 
  less 
  easily 
  

   accomplished 
  than 
  when 
  the 
  cement 
  is 
  showered 
  down 
  through 
  

   the 
  liquid. 
  The 
  temperature 
  of 
  the 
  oil 
  of 
  turpentine 
  must 
  be 
  

   known 
  but 
  need 
  not 
  be 
  fixed 
  at 
  any 
  standard 
  point, 
  and 
  after 
  

   the 
  operation 
  the 
  volumenometer, 
  which 
  is 
  stoppered 
  to 
  prevent 
  

   evaporation, 
  is 
  brought 
  to 
  the 
  same 
  temperature 
  by 
  immersion 
  

   in 
  the 
  same 
  vessel 
  of 
  water 
  as 
  that 
  used 
  for 
  the 
  stock 
  bottle 
  of 
  

   turpentine. 
  All 
  hydraulic 
  cements 
  have 
  specific 
  gravity 
  such 
  that 
  

   the 
  displacement 
  of 
  50 
  gm 
  falls 
  between 
  14 
  and 
  20 
  c. 
  c. 
  This 
  

   renders 
  the 
  graduation 
  of 
  the 
  stem 
  ample, 
  but 
  it 
  is 
  obvious 
  that 
  

   with 
  any 
  material 
  differing 
  largely 
  from 
  the 
  specific 
  gravity 
  of 
  

   three, 
  more 
  or 
  less 
  than 
  50 
  gm 
  can 
  be 
  taken 
  so 
  as 
  to 
  bring 
  the 
  

   displacement 
  within 
  its 
  range. 
  

  

  Good 
  well 
  burned 
  cement 
  as 
  it 
  comes 
  from 
  the 
  mill 
  has 
  a 
  

   specific 
  gravity 
  of 
  less 
  than 
  3.15. 
  It 
  is 
  generally 
  higher 
  than 
  

   this 
  and 
  may 
  even 
  reach 
  3.20. 
  The 
  specific 
  gravity 
  falls 
  rapidly 
  

   when 
  the 
  cement 
  is 
  aerated. 
  

  

  Structure 
  and 
  color 
  

  

  Even 
  when 
  ground 
  to 
  the 
  finest 
  degree 
  portland 
  cement 
  shows 
  

   sharp 
  grains. 
  To 
  a 
  great 
  extent 
  the 
  color 
  of 
  the 
  product 
  is 
  pro- 
  

   duced 
  by 
  a 
  combination 
  of 
  the 
  shades 
  of 
  the 
  individual 
  grains. 
  

   Naturally 
  portland 
  cement 
  should 
  be 
  white 
  but 
  this 
  becomes 
  

   covered 
  up 
  by 
  the 
  colors 
  of 
  the 
  iron 
  and 
  manganese 
  compounds 
  

   formed 
  during 
  the 
  burning. 
  

  

  Furthermore 
  when 
  fluor 
  spar 
  is 
  used 
  as 
  a 
  flux 
  it 
  develops 
  a 
  

   dirty 
  grayish 
  brown 
  color 
  in 
  the 
  clinker. 
  Sometimes 
  the 
  color 
  

   of 
  the 
  cement 
  is 
  changed 
  artificially. 
  

  

  Tests 
  

  

  In 
  addition 
  to 
  the 
  tensile 
  strength 
  test 
  of 
  portland 
  cement 
  the 
  

   hammer 
  test 
  is 
  sometimes 
  tried. 
  A 
  machine 
  has 
  been 
  devised 
  

   known 
  as 
  the 
  Bohme 
  hammer 
  machine, 
  which 
  consists 
  of 
  a 
  

   hinged 
  hammer 
  operated 
  by 
  means 
  of 
  a 
  spur 
  wheel. 
  This 
  spur 
  

   wheel 
  is 
  turned 
  by 
  means 
  of 
  a 
  crank, 
  and 
  the 
  wheel 
  acting 
  on 
  

  

  