﻿ROAD 
  MATERIALS 
  AND 
  THEIR 
  DISTRIBUTION 
  IO5 
  

  

  very 
  good 
  road 
  metal. 
  Where 
  hornblende 
  is 
  absent 
  one 
  would 
  expect 
  to 
  

   find 
  less 
  binding 
  power. 
  

  

  Granite 
  is 
  harder 
  than 
  trap 
  and 
  therefore 
  should 
  resist 
  wear 
  better, 
  but 
  

   this 
  quality 
  is 
  offset 
  by 
  its 
  usually 
  smaller 
  binding 
  power 
  due 
  to 
  the 
  

   presence 
  of 
  quartz 
  so 
  that 
  trap 
  should 
  be 
  preferred 
  as 
  a 
  rule. 
  

  

  Granite 
  is 
  found 
  in 
  the 
  Adirondack 
  region 
  and 
  in 
  the 
  Highlands 
  of 
  the 
  

   Hudson, 
  also 
  in 
  Westchester 
  county. 
  The 
  commercial 
  term 
  granite 
  in- 
  

   cludes 
  various 
  kinds 
  of 
  gneiss. 
  

  

  Magnesian 
  limestone 
  has 
  great 
  binding 
  power 
  but 
  is 
  quite 
  soft 
  and 
  

   therefore 
  not 
  very 
  durable 
  for 
  heavy 
  traffic. 
  Chemically, 
  this 
  rock 
  is 
  

   chiefly 
  a 
  carbonate 
  of 
  lime 
  also 
  containing 
  carbonate 
  of 
  magnesia, 
  alumina 
  

   and 
  silica. 
  Limestone 
  entirely 
  free 
  from 
  magnesia 
  is 
  rare. 
  

  

  It 
  has 
  been 
  suggested 
  that 
  this 
  stone 
  may 
  be 
  used 
  profitably 
  as 
  a 
  binder 
  

   over 
  stone 
  of 
  less 
  binding 
  power. 
  

  

  Limestone 
  is 
  found 
  chiefly 
  in 
  areas 
  parallel 
  to 
  and 
  near 
  the 
  main 
  line 
  

   of 
  the 
  New 
  York 
  Central 
  railroad 
  and 
  in 
  a 
  zone 
  around 
  the 
  Adirondacks. 
  

  

  Sandstone 
  consists 
  chiefly 
  of 
  quartz, 
  has 
  usually 
  no 
  lime, 
  magnesia 
  or 
  

   alumina 
  and 
  therefore 
  has 
  no 
  binding 
  properties 
  and 
  never 
  makes 
  a 
  first 
  

   rate 
  road, 
  as 
  the 
  fragments 
  continually 
  break 
  loose. 
  

  

  In 
  New 
  York 
  the 
  best 
  road 
  materials 
  occur 
  in 
  certain 
  limited 
  areas, 
  

   and 
  at 
  points 
  distant 
  from 
  these 
  the 
  cost 
  of 
  transportation 
  is 
  the 
  con- 
  

   trolling 
  feature 
  in 
  the 
  question 
  of 
  their 
  use. 
  

  

  The 
  accompanying 
  map 
  shows 
  the 
  distribution 
  of 
  the 
  areas 
  of 
  rock 
  

   already 
  mentioned 
  which 
  are 
  available 
  for 
  road 
  construction 
  in 
  New 
  

   York. 
  

  

  For 
  high 
  class 
  road 
  building, 
  trap 
  and 
  granite 
  will 
  be 
  preferred 
  and 
  

   used 
  in 
  all 
  places 
  where 
  their 
  cost 
  is 
  not 
  prohibitory. 
  Experience 
  shows, 
  

   however, 
  that 
  unless 
  these 
  materials 
  are 
  used 
  under 
  the 
  direction 
  of 
  ex- 
  

   perienced 
  road 
  engineers, 
  they 
  are 
  less 
  satisfactory 
  than 
  Hmestone, 
  and 
  

   when 
  it 
  is 
  proposed 
  to 
  macadamize 
  a 
  road 
  by 
  simply 
  covering 
  it 
  with 
  

   broken 
  stone, 
  the 
  latter 
  though 
  less 
  durable, 
  will 
  be 
  more 
  satisfactory. 
  

  

  When 
  granite 
  and 
  trap 
  are 
  properly 
  laid, 
  on 
  a 
  well 
  prepared 
  bed 
  and 
  

   rolled 
  with 
  a 
  heavy 
  steam 
  roller 
  to 
  the 
  proper 
  standard 
  of 
  firmness, 
  

   nothing 
  can 
  be 
  better, 
  but 
  where 
  no 
  steam 
  roller 
  is 
  available 
  and 
  the 
  sub- 
  

   grade 
  is 
  not 
  properly 
  prepared, 
  the 
  trap 
  and 
  granite 
  are 
  liable 
  to 
  aff"ord 
  

   only 
  an 
  unpleasant 
  and 
  uneven 
  surface 
  of 
  hard 
  angular 
  fragments 
  which 
  

   ceaselessly 
  roll 
  about 
  on 
  the 
  surface 
  of 
  the 
  road 
  injuring 
  the 
  horses 
  and 
  

   making 
  pleasure 
  driving 
  impossible. 
  

  

  Limestone 
  from 
  its 
  softness 
  and 
  greater 
  binding 
  power 
  is 
  more 
  easily 
  

   rolled 
  into 
  an 
  even 
  surface 
  under 
  the 
  wheels 
  of 
  vehicles, 
  and 
  while 
  not 
  

  

  