﻿502 
  IsTEAV 
  YOEK 
  STATE 
  MUSEUM 
  

  

  are 
  known 
  as 
  shale. 
  Shales 
  simply 
  represent 
  the 
  finest 
  clay 
  sedi- 
  

   ment, 
  whicli 
  has 
  been 
  deposited 
  in 
  those 
  parts 
  of 
  the 
  ocean 
  which 
  

   are 
  very 
  quiet 
  and 
  has 
  become 
  consolidated 
  by 
  the 
  pressure 
  of 
  other 
  

   sediments 
  laid 
  upon 
  it. 
  In 
  some 
  hard 
  shales 
  there 
  is 
  probably 
  also 
  

   some 
  cementing 
  material 
  between 
  the 
  grains. 
  

  

  In 
  the 
  later 
  discussion 
  of 
  the 
  chemical 
  and 
  physical 
  properties 
  of 
  

   clay 
  whatever 
  is 
  said 
  of 
  clay 
  mil 
  also 
  apply 
  to 
  shale, 
  unless 
  it 
  be 
  

   otherwise 
  stated. 
  

  

  Shales 
  w^hen 
  ground 
  up 
  and 
  mixed 
  with 
  water 
  generally 
  produce 
  

   a 
  plastic 
  mass 
  similar 
  to 
  common 
  clays. 
  If 
  simply 
  placed 
  in 
  water, 
  

   however, 
  they 
  do 
  not 
  usually 
  fall 
  to 
  pieces 
  as 
  an 
  ordinary 
  clay 
  does, 
  

   or, 
  in 
  other 
  words, 
  they 
  do 
  not 
  slake. 
  Shales 
  may 
  be 
  either 
  highly 
  

   refractory 
  or 
  extremely 
  fusible, 
  and 
  both 
  forms 
  of 
  this 
  material 
  

   are 
  of 
  commercial 
  value. 
  Some 
  of 
  the 
  most 
  refractory 
  material 
  

   mined 
  in 
  the 
  United 
  States, 
  as 
  for 
  instance 
  the 
  fire 
  clays 
  found 
  

   at 
  Denvei* 
  Col., 
  or 
  those 
  in 
  Pennsylvania, 
  are 
  shales. 
  The 
  chief 
  

   use 
  of 
  shales 
  in 
  the 
  United 
  States 
  is 
  in 
  the 
  manufacture 
  of 
  paving 
  

   bricks. 
  Those 
  of 
  ^ew 
  York 
  state 
  are 
  treated 
  in 
  a 
  separate 
  

   chapter. 
  

  

  