﻿LIMESTONES 
  OP 
  NEW 
  YORK 
  AND 
  THEIR 
  ECONOMIC 
  VALUE 
  397 
  

  

  Burning 
  of 
  natural 
  rock 
  cemewt. 
  a 
  In 
  America 
  the 
  sheet 
  iron 
  kiln 
  

   is 
  frequently 
  used. 
  In 
  the 
  Rosendale 
  district 
  an 
  elaborate 
  system 
  

   of 
  mining 
  is 
  conducted 
  to 
  get 
  out 
  the 
  raw 
  material. 
  The 
  raw 
  

   material 
  occurs 
  generally 
  in 
  two 
  beds 
  of 
  rock 
  known 
  as 
  the 
  dark 
  

   rock 
  and 
  the 
  light 
  rock. 
  These 
  beds 
  vary 
  in 
  thickness, 
  but 
  gen- 
  

   erally 
  the 
  former 
  is 
  about 
  18 
  feet 
  thick 
  and 
  the 
  latter 
  12 
  feet, 
  and 
  

   there 
  are 
  barren 
  layers 
  about 
  10 
  to 
  15 
  feet 
  thick 
  separating 
  the 
  

   two 
  cement 
  deposits. 
  As 
  the 
  formations 
  have 
  been 
  very 
  much 
  dis- 
  

   turbed 
  in 
  Ulster 
  co. 
  N. 
  Y. 
  the 
  cement 
  beds 
  are 
  found 
  dipping 
  

   more 
  or 
  less 
  steeply. 
  Under 
  these 
  conditions 
  with 
  comparatively 
  

   small 
  beds 
  of 
  productive 
  rock 
  in 
  a 
  mountainous 
  district 
  it 
  soon 
  

   becomes 
  unprofitable 
  to 
  work 
  the 
  cement 
  in 
  open 
  quarry. 
  The 
  

   natural 
  development 
  therefore 
  has 
  been 
  a 
  resort 
  to 
  mining 
  by 
  a 
  

   system 
  of 
  slopes 
  and 
  headings 
  similar 
  in 
  general 
  scheme 
  to 
  

   anthracite 
  coal 
  mining 
  in 
  Pennsylvania. 
  This 
  work 
  is 
  evidently 
  

   expensive 
  and 
  would 
  be 
  much 
  more 
  so 
  if 
  it 
  were 
  not 
  that 
  the 
  

   rock 
  coming 
  from 
  these 
  light 
  and 
  dark 
  strata 
  is 
  practically 
  all 
  

   of 
  it 
  available 
  for 
  making 
  cement 
  and 
  requires 
  comparatively 
  

   little 
  sorting 
  or 
  separating 
  after 
  it 
  is 
  mined. 
  As 
  the 
  boundaries 
  

   of 
  the 
  beds 
  are 
  sharp 
  very 
  little 
  useless 
  rock 
  has 
  to 
  be 
  quarried. 
  

   Such 
  things 
  also 
  contribute 
  to 
  reduce 
  the 
  cost. 
  Power-drills 
  are 
  

   generally 
  employed 
  in 
  the 
  Rosendale 
  mines 
  with 
  high 
  explosives 
  

   to 
  displace 
  the 
  rock. 
  Some 
  of 
  the 
  mines 
  have 
  a 
  great 
  deal 
  of 
  

   water 
  which 
  requires 
  to 
  be 
  pumped 
  regularly 
  to 
  keep 
  the 
  head- 
  

   ings 
  dry. 
  According 
  to 
  Mr 
  Lewis 
  a 
  somewhat 
  similar 
  system 
  of 
  

   mining 
  is 
  resorted 
  to 
  in 
  Cumberland, 
  Md. 
  In 
  Pennsylvania 
  (the 
  

   Lehigh 
  district) 
  the 
  work 
  is 
  all 
  done 
  in 
  open 
  quarry 
  on 
  large 
  de- 
  

   posits 
  of 
  suitable 
  rock, 
  requiring 
  little 
  stripping 
  or 
  sorting. 
  

  

  The 
  kilns 
  used 
  on 
  natural 
  cement 
  are 
  all 
  of 
  the 
  lime-kiln 
  type. 
  

   That 
  is, 
  the 
  shaft 
  is 
  generally 
  cylindrical, 
  drawn 
  into 
  a 
  hopper 
  at 
  

   the 
  bottom 
  and 
  open 
  at 
  the 
  top. 
  The 
  rock 
  without 
  any 
  prelimi- 
  

   nary 
  preparation, 
  is 
  charged 
  at 
  the 
  top 
  in 
  alternate 
  layers 
  with 
  

   coal 
  and 
  the 
  clinker 
  is 
  drawn 
  at 
  the 
  bottom. 
  The 
  operation 
  is 
  

   continuous 
  and 
  as 
  the 
  temperature 
  of 
  calcination 
  is 
  compara- 
  

  

  aMuch 
  of 
  the 
  information 
  relating 
  to 
  this 
  subject 
  has 
  been 
  taken 
  from 
  Mineral 
  

   industry, 
  v. 
  7. 
  

  

  