﻿104 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  gutter 
  at 
  road 
  intersections 
  unless 
  some 
  person 
  were 
  detailed 
  to 
  keep 
  it 
  in 
  

   continuous 
  repair. 
  As 
  this 
  has 
  not 
  yet 
  been 
  found 
  practicable 
  on 
  public 
  

   roads, 
  the 
  gutter 
  bridge 
  is 
  everywhere 
  in 
  use, 
  and 
  in 
  the 
  spring 
  it 
  is 
  a 
  

   fruitful 
  source 
  of 
  injury 
  to 
  the 
  road. 
  It 
  will 
  be 
  seen 
  from 
  every 
  day 
  obser- 
  

   vation 
  and 
  from 
  the 
  details 
  stated 
  above 
  that 
  the 
  earth 
  road 
  while 
  as 
  yet 
  

   all 
  that 
  the 
  people 
  have 
  agreed 
  to 
  have 
  in 
  New 
  York 
  has 
  necessarily 
  

   many 
  elements 
  of 
  self-destruction 
  and 
  can 
  never 
  be 
  regarded 
  as 
  permanent. 
  

   The 
  development 
  of 
  the 
  wheel 
  scraper 
  or 
  road 
  machine 
  has 
  made 
  it 
  

   possible 
  however 
  to 
  keep 
  an 
  earth 
  road 
  in 
  good 
  condition 
  if 
  intelligently 
  

   used. 
  

  

  For 
  speedways 
  and 
  pleasure 
  driving 
  in 
  general, 
  a 
  well 
  kept 
  earth 
  road 
  

   in 
  dry 
  weather 
  is 
  superior 
  to 
  all 
  others. 
  The 
  perfect 
  Macadam 
  or 
  Tel- 
  

   ford 
  road 
  is 
  too 
  hard 
  to 
  permit 
  of 
  very 
  fast 
  driving 
  without 
  injury 
  to 
  the 
  

   feet 
  of 
  horses. 
  

  

  Road 
  Materials 
  and 
  their 
  Distribution 
  

  

  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 
  regular 
  manner 
  in 
  which 
  

   the 
  rock 
  is 
  jointed. 
  

  

  The 
  trap 
  which 
  is 
  used 
  in 
  New 
  York 
  for 
  a 
  road 
  metal 
  iS 
  a 
  diabase 
  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 
  cementing 
  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 
  consid- 
  

   erable 
  extent. 
  

  

  This 
  property 
  is 
  most 
  noticeable 
  in 
  rocks 
  containing 
  much 
  lime, 
  mag- 
  

   nesia 
  and 
  alumina. 
  

  

  Good 
  trap 
  is 
  known 
  only 
  in 
  Richmond 
  and 
  Rockland 
  counties, 
  and 
  in 
  

   the 
  intermediate 
  area 
  of 
  New 
  Jersey 
  bordering 
  the 
  Hudson 
  river. 
  Its 
  

   very 
  prominent 
  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 
  the 
  same 
  composi- 
  

   tion 
  as 
  augite 
  which 
  occurs 
  in 
  trap 
  ; 
  and 
  a 
  hornblende 
  granite 
  should 
  be 
  a 
  

  

  