﻿752 
  NEW 
  YOEK 
  STATE 
  MUSEUM 
  

  

  3 
  Removing 
  the 
  irregularities 
  of 
  surface 
  and 
  crushing 
  between 
  

   straw 
  boards. 
  

  

  4 
  Removing 
  irregularities, 
  coating 
  with 
  plaster 
  of 
  paris 
  and 
  

   placing 
  under 
  slight 
  pressure 
  till 
  set 
  (12-24 
  hrs), 
  and 
  then 
  

   crushing. 
  

  

  5 
  Coating 
  with 
  plaster 
  of 
  paris 
  which 
  was 
  afterward 
  ground 
  

   down, 
  on 
  a 
  sand 
  paper 
  disk, 
  to 
  the 
  surface 
  of 
  the 
  brick 
  so 
  as 
  to 
  

   leave 
  a 
  minimum 
  thickness 
  with 
  a 
  perfectly 
  flat 
  surface, 
  and 
  then 
  

   crushing. 
  

  

  After 
  a 
  number 
  of 
  experiments 
  no 
  great 
  difference 
  was 
  found 
  

   between 
  the 
  first 
  three, 
  but 
  difficulties 
  connected 
  with 
  the 
  last 
  

   two 
  rendered 
  them 
  worthless. 
  With 
  a 
  uniform 
  grade 
  of 
  brick 
  

   the 
  first 
  three 
  methods 
  gave 
  7000 
  to 
  9000 
  pounds 
  as 
  the 
  crushing 
  

   strength 
  of 
  cubes. 
  Some 
  samples 
  of 
  the 
  same 
  lot 
  of 
  brick 
  were 
  

   prepared 
  on 
  a 
  rubbing 
  bed 
  at 
  marble 
  works, 
  and 
  the 
  strength 
  of 
  

   these 
  carefully 
  prepared 
  cubes 
  ranged 
  from 
  16,000 
  to 
  21,000 
  

   pounds 
  a 
  square 
  inch, 
  showing 
  that 
  a 
  very 
  small 
  difference 
  in 
  fiat- 
  

   ness 
  of 
  surface 
  makes 
  a 
  great 
  difference 
  in 
  the 
  apparent 
  strength. 
  

  

  At 
  a 
  recent 
  meeting 
  of 
  the 
  isTational 
  brick 
  manufacturers 
  asso- 
  

   ciation, 
  Gomer 
  Jones, 
  city 
  engineer 
  of 
  Geneva, 
  E". 
  Y., 
  advocated 
  

   the 
  following 
  method 
  for 
  testing 
  the 
  resistance 
  of 
  paving 
  brick 
  to 
  

   abrasion. 
  

  

  A 
  rattler 
  of 
  the 
  usual 
  type 
  has 
  the 
  staves 
  fitted 
  with 
  two 
  longi- 
  

   tudinal 
  pockets 
  each, 
  in 
  which 
  the 
  bricks 
  are 
  inserted 
  and 
  held 
  end 
  

   to 
  end. 
  These 
  pockets 
  are 
  3 
  inches 
  deep, 
  leaving 
  about 
  one 
  inch 
  of 
  

   brick 
  protruding. 
  " 
  When 
  all 
  the 
  staves 
  are 
  in 
  place, 
  the 
  interior 
  

   of 
  the 
  rattler 
  is 
  virtually 
  solid 
  brick 
  lined. 
  During 
  rotation 
  the 
  

   attack 
  of 
  the 
  abrading 
  material 
  is 
  at 
  right 
  angles 
  to 
  the 
  length 
  of 
  

   the 
  brick, 
  and 
  confined 
  to 
  the 
  surfaces 
  and 
  edges 
  which 
  are 
  ex- 
  

   posed 
  in 
  actual 
  use; 
  there 
  is 
  sufficient 
  space 
  between 
  the 
  brick 
  for 
  

   the 
  escape 
  of 
  any 
  dust 
  or 
  waste, 
  and 
  incidentally 
  allowing 
  the 
  

   abrading 
  material 
  free 
  access 
  to 
  the 
  unsupported 
  edges 
  of 
  the 
  

   brick 
  under 
  test, 
  thus 
  establishing 
  the 
  conditions 
  of 
  position 
  and 
  

  

  