﻿TESTS 
  OF 
  ROAD 
  MATERIAL 
  III 
  

  

  As 
  shown 
  by 
  the 
  preceding 
  table, 
  the 
  New 
  York 
  rocks 
  tested 
  in 
  the 
  

   laboratory 
  of 
  the 
  Massachusetts 
  Highway 
  Commission 
  were 
  only 
  sub- 
  

   jected 
  to 
  the 
  abrasion 
  test 
  and 
  therefore 
  the 
  results 
  can 
  not 
  be 
  fully 
  com- 
  

   pared 
  with 
  the 
  tests 
  of 
  the 
  Massachusetts 
  rocks 
  which 
  are 
  given 
  above. 
  

   Two 
  samples 
  of 
  traps 
  were 
  tested, 
  one 
  from 
  the 
  Bouker 
  quarry 
  at 
  Gutten- 
  

   burg 
  and 
  one 
  from 
  the 
  quarry 
  of 
  Conklin 
  & 
  Foss 
  at 
  Rockland 
  Lake. 
  The 
  

   specimen 
  tested 
  from 
  the 
  Bouker 
  quarry 
  proved 
  to 
  be 
  very 
  much 
  harder 
  

   than 
  that 
  from 
  the 
  Conklin 
  & 
  Foss 
  quarry. 
  There 
  are 
  two 
  varieties 
  of 
  

   trap 
  found 
  in 
  the 
  Bouker 
  quarry 
  ; 
  one 
  being 
  considered 
  of 
  inferior 
  quahty 
  

   and 
  known 
  by 
  the 
  quarrymen 
  as 
  '•^ 
  false 
  trap.^^ 
  It 
  is 
  part 
  of 
  the 
  lower 
  

   portion 
  of 
  the 
  trap 
  mass 
  and 
  being 
  near 
  the 
  sandstone 
  which 
  forms 
  its 
  lower 
  

   foundation, 
  it 
  cooled 
  more 
  rapidly 
  and 
  assumed 
  a 
  finer 
  texture 
  and 
  a 
  

   harder 
  condition 
  than 
  the 
  mass 
  above. 
  Although 
  this 
  so-called 
  false 
  trap 
  

   has 
  not 
  been 
  subjected 
  to 
  a 
  cementation 
  test, 
  one 
  \^;ould 
  expect 
  it 
  to 
  

   prove 
  equally 
  valuable 
  with 
  the 
  rest 
  in 
  this 
  respect, 
  as 
  its 
  chemical 
  com- 
  

   position 
  is 
  probably 
  nearly 
  identical 
  with 
  that 
  of 
  the 
  softer 
  trap 
  imme- 
  

   diately 
  adjoining. 
  It 
  was 
  a 
  sample 
  of 
  the 
  " 
  false 
  trap 
  " 
  which 
  was 
  tested. 
  

  

  It 
  is 
  stated 
  that 
  where 
  used 
  at 
  some 
  points 
  on 
  Long 
  Island 
  it 
  has 
  

   proven 
  unsatisfactory, 
  the 
  fragments 
  not 
  holding 
  together 
  and 
  forming 
  an 
  

   even 
  surface, 
  but 
  frequently 
  flying 
  out. 
  

  

  The 
  attention 
  of 
  the 
  writer 
  has 
  been 
  called 
  to 
  this 
  fact, 
  but 
  he 
  has 
  not 
  

   sufficient 
  information 
  to 
  warrant 
  a 
  full 
  expression 
  of 
  opinion. 
  The 
  difii- 
  

   culty 
  may 
  be 
  due 
  to 
  improper 
  construction 
  in 
  building 
  the 
  road. 
  It 
  

   might 
  also 
  be 
  due 
  to 
  the 
  mixture 
  of 
  this 
  harder 
  variety 
  of 
  trap 
  and 
  softer 
  

   material 
  from 
  the 
  same 
  quarry, 
  it 
  being 
  well 
  established 
  by 
  experience 
  

   that 
  unless 
  the 
  road-metal 
  in 
  the 
  surface 
  layer 
  is 
  of 
  uniform 
  hardness, 
  

   it 
  will 
  not 
  wear 
  uniformly. 
  To 
  establish 
  the 
  truth 
  in 
  this 
  case 
  would 
  in- 
  

   volve 
  a 
  good 
  deal 
  of 
  experimental 
  work 
  for 
  which 
  no 
  funds 
  are 
  available, 
  

   but 
  theorizing 
  on 
  the 
  facts 
  accessible, 
  there 
  seems 
  no 
  reason 
  why 
  the 
  

   harder 
  trap 
  or 
  false 
  trap 
  should 
  not 
  make 
  a 
  good 
  road 
  provided 
  it 
  is 
  kept 
  

   separate 
  from 
  material 
  of 
  different 
  hardness 
  and 
  is 
  laid 
  under 
  the 
  super- 
  

   vision 
  of 
  a 
  competent 
  engineer. 
  

  

  As 
  a 
  rule 
  when 
  it 
  is 
  not 
  possible 
  to 
  make 
  numerous 
  tests 
  and 
  experi- 
  

   ments, 
  it 
  v/ill 
  be 
  cheaper 
  to 
  use 
  those 
  materials 
  which 
  have 
  proven 
  satis- 
  

   factory 
  in 
  actual 
  use. 
  

  

  Owing 
  to 
  the 
  press 
  of 
  state 
  work 
  it 
  was 
  not 
  possible 
  for 
  the 
  Massachu- 
  

   setts 
  commission 
  to 
  make 
  cementation 
  tests 
  of 
  the 
  specimens 
  submitted. 
  

   The 
  tests 
  made, 
  confirm 
  the 
  results 
  of 
  practical 
  experience 
  and 
  show 
  that 
  

   granite, 
  trap 
  and 
  sandstone 
  are 
  harder 
  and 
  offer 
  more 
  resistance 
  to 
  abra- 
  

   sion 
  than 
  the 
  limestones. 
  The 
  cementation 
  test, 
  when 
  made, 
  would 
  un- 
  

   questionably 
  show 
  the 
  highest 
  cementing 
  value 
  to 
  be 
  in 
  the 
  limestone, 
  

   trap 
  and 
  granite 
  and 
  the 
  lowest 
  in 
  the 
  sandstone. 
  

  

  