﻿CLAYS 
  OF 
  Is^EW 
  YOKK 
  825 
  

  

  SHALES 
  OF 
  NEW 
  YOEK 
  

  

  Tliese 
  form 
  an 
  enormous 
  series 
  of 
  deposits 
  in 
  the 
  soutliem 
  region 
  

   of 
  the 
  state, 
  as 
  well 
  as 
  some 
  of 
  the 
  central 
  portions. 
  

  

  The 
  origin 
  of 
  shale 
  has 
  already 
  been 
  mentioned 
  (p. 
  502). 
  From 
  

   the 
  fa.ct 
  that 
  they 
  were 
  deposited 
  in 
  the 
  sea 
  thev 
  are 
  nsnally 
  much 
  

   more 
  extensive 
  than 
  the 
  Quaternary 
  clays 
  immediately 
  underhdng 
  

   the 
  surface. 
  

  

  The 
  shales 
  found 
  in 
  Ise^v 
  York 
  state 
  are 
  in 
  every 
  case 
  quite 
  

   impure, 
  and 
  often 
  silicious, 
  indeed 
  are 
  at 
  times 
  interbedded 
  with 
  

   thin 
  layers 
  of 
  sandstone. 
  Owing 
  to 
  their 
  consolidated 
  nature 
  the 
  

   shales 
  have 
  to 
  be 
  first 
  ground 
  in 
  order 
  to 
  develop 
  their 
  plasticity; 
  

   the 
  finer 
  the 
  grinding 
  the 
  more 
  plastic 
  the 
  mass. 
  It 
  has 
  also 
  been 
  

   found 
  that 
  in 
  some 
  cases 
  the 
  finer 
  grinding 
  of 
  the 
  shale 
  produces 
  a 
  

   vitrified 
  brick 
  at 
  a 
  temperature 
  that 
  formerly 
  did 
  not 
  allow 
  this, 
  

   the 
  brick 
  made 
  from 
  the 
  coarser 
  shale 
  showing 
  6^-7^ 
  absorption. 
  

  

  Shales 
  exhibit 
  a 
  great 
  variation 
  in 
  hardness 
  ; 
  this 
  fact 
  shows 
  itself 
  

   specially 
  during 
  the 
  grinding 
  process. 
  As 
  has 
  been 
  stated 
  in 
  an- 
  

   other 
  place, 
  shale 
  is 
  only 
  a 
  consolidated 
  clay. 
  Sometimes 
  this 
  hard- 
  

   ening 
  or 
  consolidation 
  has 
  occurred 
  by 
  the 
  weight 
  of 
  the 
  overlying 
  

   beds 
  alone, 
  while 
  at 
  other 
  times 
  the 
  clay 
  particles 
  have 
  become 
  more 
  

   or 
  less 
  cemented 
  together. 
  It 
  is 
  obvious, 
  therefore, 
  that 
  those 
  

   shales 
  hardened 
  by 
  the 
  former 
  circumstance 
  will 
  fall 
  apart 
  more 
  

   readily 
  in 
  the 
  grinding 
  pan, 
  and 
  tend 
  to 
  yield 
  a 
  more 
  plastic 
  mass. 
  

  

  So 
  far 
  as 
  the 
  shales 
  have 
  been 
  used 
  and 
  tested, 
  the 
  Devonian 
  

   shales 
  seem 
  to 
  work 
  best 
  for 
  a 
  vitrified 
  product, 
  as 
  the 
  points 
  of 
  in- 
  

   cipient 
  fusion 
  lie 
  from 
  250 
  to 
  300° 
  F. 
  apart. 
  

  

  The 
  Salina 
  shales 
  make 
  a 
  good 
  strong 
  brick 
  if 
  thorough 
  vitrifica- 
  

   tion 
  is 
  not 
  desired, 
  for 
  they 
  are 
  often 
  calcareous. 
  

  

  The 
  Medina 
  shales, 
  particularly 
  the 
  weathered 
  portions, 
  are 
  util- 
  

   ized 
  in 
  Ontario 
  for 
  making 
  pressed 
  brick 
  and 
  give 
  good 
  results. 
  The 
  

   deposit 
  continued 
  across 
  west 
  central 
  Xew^ 
  York 
  awaits 
  develop- 
  

   ment. 
  

  

  