﻿LIMESTONES 
  OP 
  NEW 
  YORK 
  AND 
  THEIR 
  ECONOMIC 
  VALUE 
  393 
  

  

  draulic 
  cements. 
  As 
  said 
  before 
  natural 
  cements 
  are 
  made 
  from 
  

   limestone 
  which 
  contains 
  an 
  admixture 
  of 
  silica, 
  clay 
  and 
  mag- 
  

   nesia. 
  The 
  natural 
  hydraulic 
  limestone 
  found 
  in 
  the 
  United 
  

   States 
  however 
  varies 
  considerably 
  in 
  composition. 
  

  

  The 
  hydraulic 
  limestone 
  can 
  be 
  divided 
  into 
  two 
  classes 
  based 
  

   on 
  the 
  different 
  amounts 
  of 
  carbonate 
  of 
  magnesia 
  which 
  they 
  

   contain. 
  In 
  one 
  class 
  it 
  does 
  not 
  exceed 
  3$ 
  or 
  4$, 
  in 
  another 
  15 
  

   to 
  35$ 
  is 
  found. 
  Most 
  of 
  the 
  hydraulic 
  limestone 
  of 
  the 
  United 
  

   States 
  is 
  magnesian 
  but 
  that 
  of 
  the 
  Lehigh 
  valley 
  and 
  the 
  upper 
  

   Potomac 
  valley 
  is 
  not. 
  Likewise 
  some 
  of 
  the 
  deposits 
  of 
  the 
  west, 
  

   hut 
  it 
  can 
  be 
  said 
  in 
  general 
  that 
  over 
  90$ 
  of 
  the 
  rock 
  used 
  is 
  

   magnesian. 
  The 
  Eosendale 
  and 
  the 
  Louisville 
  cements 
  contain 
  

   15 
  to 
  25$ 
  of 
  magnesia. 
  The 
  amount 
  of 
  the 
  two 
  carbonates 
  in 
  

   the 
  two 
  limestones 
  varies 
  from 
  54 
  to 
  75$, 
  while 
  silicates 
  and 
  silica 
  

   may 
  vary 
  from 
  20 
  to 
  47$. 
  The 
  rock 
  may 
  also 
  vary 
  in 
  one 
  locality 
  . 
  a 
  

  

  It 
  often 
  happens 
  that 
  the 
  different 
  strata 
  of 
  hydraulic 
  limestone 
  

   in 
  any 
  one 
  quarry 
  are 
  not 
  all 
  equally 
  well 
  suited 
  for 
  making 
  

   natural 
  cement, 
  so 
  that 
  before 
  entering 
  into 
  any 
  quarrying 
  

   method 
  which 
  involves 
  the 
  mixing 
  of 
  all 
  the 
  beds 
  the 
  availability 
  

   ■of 
  the 
  different 
  ones 
  should 
  be 
  determined 
  beforehand 
  by 
  experi- 
  

   ment. 
  Their 
  adaptability 
  depends 
  on 
  the 
  amount 
  of 
  silica 
  and 
  

   silicates 
  which 
  they 
  contain 
  and 
  also 
  on 
  the 
  percentage 
  of 
  mag- 
  

   nesia 
  and 
  also 
  sometimes 
  on 
  the 
  percentage 
  of 
  sulfur 
  and 
  alka- 
  

   lies. 
  In 
  addition 
  the 
  silica 
  should 
  be 
  combined 
  with 
  the 
  alumina, 
  

   and 
  the 
  rock 
  should 
  also 
  be 
  dense. 
  The 
  two 
  classes 
  of 
  natural 
  

   cement 
  mentioned 
  above, 
  namely 
  the 
  magnesian 
  and 
  the 
  non- 
  

   magnesian 
  differ 
  distinctly 
  in 
  other 
  properties. 
  The 
  magnesia 
  

   cements 
  do 
  not 
  heat 
  on 
  mixing 
  and 
  with 
  water 
  they 
  set 
  and 
  

   strengthen 
  slowly 
  but 
  in 
  the 
  end 
  are 
  as 
  strong 
  as 
  the 
  lime 
  

   cements. 
  They 
  do 
  not 
  resist 
  frost 
  well 
  when 
  first 
  used, 
  and 
  often 
  

   careful 
  preparations 
  have 
  a 
  tendency 
  to 
  expand 
  a 
  year 
  or 
  two 
  

   after 
  use. 
  The 
  lime 
  cements 
  when 
  carefully 
  made 
  have 
  a 
  ten- 
  

   dency 
  when 
  made 
  into 
  mortar 
  to 
  heat 
  on 
  the 
  one 
  hand 
  when 
  too 
  

   rich 
  in 
  lime 
  and 
  on 
  the 
  other 
  hand 
  to 
  bloat 
  when 
  too 
  rich 
  in 
  

   silicates 
  or 
  overburned. 
  They 
  acquire 
  strength 
  rapidly, 
  having 
  

  

  aRichardson 
  gives 
  analyses 
  of 
  different 
  strata 
  in 
  a 
  Maryland 
  quarry, 
  Brickbuilder, 
  

   1897, 
  p. 
  152. 
  L, 
  ,. 
  ,..,._ 
  . 
  ., 
  . 
  

  

  