﻿396 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  limestone, 
  and 
  as 
  said 
  before 
  the 
  silica 
  should 
  be 
  in 
  combi- 
  

   nation 
  with 
  the 
  alumina. 
  Can 
  this 
  case 
  be 
  determined 
  partly 
  

   from 
  the 
  quantity 
  of 
  alumina 
  contained 
  in 
  the 
  stone? 
  For 
  

   example 
  two 
  stones, 
  one 
  from 
  Akron, 
  N. 
  Y. 
  and 
  the 
  other 
  

   from 
  the 
  Rosendale 
  region 
  show 
  according 
  to 
  Richardson 
  respec- 
  

   tively 
  35$ 
  and 
  29$ 
  of 
  insoluble 
  material, 
  but 
  from 
  the 
  amount 
  of 
  

   alumina 
  and 
  iron 
  present 
  we 
  can 
  see 
  that 
  there 
  is 
  very 
  little 
  

   clay 
  in 
  the 
  Akron 
  stone, 
  while 
  there 
  is 
  much 
  of 
  it 
  in 
  the 
  Rosen- 
  

   dale 
  stone, 
  the 
  former 
  having 
  only 
  4.84 
  of 
  alumina 
  and 
  iron, 
  while 
  

   the 
  other 
  has 
  10$. 
  The 
  Rosendale 
  in 
  consequence 
  makes 
  a 
  very 
  

   superior 
  cement, 
  while 
  the 
  Akron 
  shows 
  the 
  qualities 
  resulting 
  

   from 
  a 
  deficiency 
  in 
  clay 
  but 
  an 
  excess 
  of 
  magnesia. 
  The 
  effect 
  

   of 
  this 
  deficiency 
  in 
  clay 
  is 
  to 
  form 
  a 
  cement 
  which 
  heats 
  and 
  sets 
  

   too 
  quickly, 
  but 
  an 
  excess 
  of 
  clay 
  can 
  also 
  be 
  injurious 
  as 
  already 
  

   stated. 
  Sulfur 
  when 
  present 
  in 
  the 
  limestone 
  is 
  generally 
  in 
  

   the 
  form 
  of 
  gypsum, 
  namely 
  sulfate' 
  of 
  lime 
  or 
  pyrites 
  or 
  iron 
  

   fiulfid. 
  , 
  Both 
  of 
  these 
  substances 
  are 
  seldom 
  present 
  in 
  suffi- 
  

   cient 
  amounts 
  to 
  be 
  injurious. 
  They 
  may 
  occasionally 
  become 
  

   reduced 
  in 
  burning 
  when 
  combined 
  with 
  iron 
  oxid 
  to 
  produce 
  a 
  

   green 
  color. 
  Alkalies 
  such 
  as 
  potash 
  and 
  soda 
  are 
  harmless 
  un- 
  

   less 
  present 
  in 
  more 
  than 
  2$; 
  an 
  excess 
  of 
  them 
  makes 
  the 
  rock 
  

   fusible 
  and 
  such 
  material 
  has 
  to 
  be 
  rejected. 
  The 
  following 
  alka- 
  

   lies 
  percentages 
  in 
  different 
  natural 
  rock 
  cement 
  is 
  given 
  by 
  

  

  Richardson. 
  

  

  Alkalies 
  in 
  hydraulic 
  cements 
  

  

  Milwaukee, 
  K 
  2 
  87 
  

  

  Milwaukee, 
  Na 
  2 
  1 
  . 
  64 
  

  

  Fort 
  Scott, 
  K 
  2 
  70 
  

  

  Fort 
  Scott, 
  Na 
  2 
  1 
  .33 
  

  

  Akron, 
  Star, 
  K 
  2 
  1 
  .39 
  

  

  Akron, 
  Star. 
  Na 
  2 
  .23 
  

  

  Akron, 
  Obelisk, 
  K 
  2 
  1 
  .60 
  

  

  Akron, 
  Obelisk, 
  Na 
  2 
  .52 
  

  

  Buffalo, 
  K 
  2 
  1 
  .44 
  

  

  Buffalo, 
  Na 
  2 
  41 
  

  

  The 
  formation 
  of 
  one 
  of 
  these 
  alkalies 
  over 
  the 
  other 
  depends 
  

   on 
  the 
  species 
  of 
  feldspar 
  from 
  which 
  it 
  is 
  derived. 
  

  

  