﻿204 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  The 
  stone 
  of 
  the 
  drift 
  is 
  generally 
  hard 
  and 
  durable, 
  having 
  

   resisted 
  the 
  wear 
  of 
  rough 
  transportation. 
  The 
  economic 
  use 
  of 
  

   the 
  surface 
  stones 
  of 
  the 
  drift 
  in 
  constructive 
  work, 
  where 
  they 
  

   can 
  be 
  laid 
  up 
  in 
  walls, 
  is 
  a 
  desirable 
  utilization 
  of 
  what 
  is 
  still 
  

   in 
  many 
  parts 
  of 
  the 
  state 
  worse 
  than 
  waste 
  — 
  a 
  nuisance 
  in 
  the 
  

   tilling 
  of 
  the 
  soil. 
  This 
  formation 
  can 
  not, 
  however, 
  be 
  con- 
  

   sidered 
  as 
  one 
  of 
  the 
  important 
  sources 
  of 
  stone 
  in 
  the 
  quarry 
  

   industry, 
  although 
  capable 
  of 
  yielding 
  a 
  great 
  deal 
  of 
  rough 
  

   stone. 
  It 
  will 
  no 
  doubt 
  do 
  so 
  in 
  the 
  future 
  clearing 
  and 
  improve- 
  

   ment 
  of 
  the 
  country. 
  

  

  Road 
  Metal 
  

  

  In 
  New 
  York 
  the 
  best 
  materials 
  for 
  road 
  metal 
  are 
  trap, 
  granite 
  

   and 
  magnesian 
  limestone. 
  

  

  Trap 
  is 
  a 
  general 
  term 
  for 
  some 
  of 
  the 
  basic 
  eruptive 
  rocks, 
  the 
  

   word 
  being 
  related 
  to 
  or 
  derived 
  from 
  the 
  German 
  Treppen 
  which 
  

   signifies 
  a 
  flight 
  of 
  steps 
  and 
  is 
  suggested 
  by 
  the 
  somewhat 
  regu- 
  

   lar 
  manner 
  in 
  which 
  the 
  rock 
  is 
  jointed. 
  

  

  The 
  trap 
  which 
  is 
  used 
  in 
  New 
  York 
  for 
  a 
  road 
  metal 
  is 
  a 
  dia- 
  

   base 
  and 
  consists 
  chiefly 
  of 
  the 
  minerals 
  augite 
  and 
  labradorite, 
  

   the 
  former 
  being 
  a 
  silicate 
  of 
  iron 
  and 
  magnesia 
  and 
  the 
  latter 
  

   being 
  a 
  lime-soda 
  feldspar. 
  Other 
  minerals 
  are 
  present 
  in 
  small 
  

   quantity 
  but 
  do 
  not 
  influence 
  the 
  properties 
  which 
  make 
  the 
  rock 
  

   valuable 
  as 
  a 
  road 
  metal. 
  

  

  While 
  sufficiently 
  hard 
  to 
  resist 
  the 
  wear 
  of 
  heavy 
  traffic 
  to 
  a 
  

   satisfactory 
  extent, 
  it 
  possesses 
  a 
  high 
  degree 
  of 
  binding 
  or 
  

   cementation 
  power. 
  This 
  means 
  that 
  the 
  dust 
  produced 
  by 
  wear 
  

   when 
  moistened 
  unites 
  quite 
  firmly 
  and 
  forms 
  a 
  cement 
  which 
  

   binds 
  the 
  larger 
  fragments 
  to 
  a 
  considerable 
  extent. 
  

  

  This 
  property 
  is 
  most 
  noticeable 
  in 
  rocks 
  containing 
  much 
  lime, 
  

   magnesia 
  and 
  alumina. 
  

  

  Good 
  trap 
  is 
  found 
  only 
  in 
  Richmond 
  and 
  Rockland 
  counties, 
  

   and 
  in 
  the 
  intermediate 
  area 
  of 
  New 
  Jersey 
  bordering 
  the 
  Hudson 
  

   river. 
  Its 
  outcrop 
  is 
  known 
  as 
  the 
  ^ 
  Palisades.' 
  

  

  Granite 
  consists 
  chiefly 
  of 
  quartz 
  mixed 
  with 
  one 
  or 
  more 
  of 
  the 
  

   feldspars 
  and 
  hornblende 
  or 
  a 
  mica. 
  Hornblende 
  has 
  essentially 
  

  

  