﻿628 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  "^ 
  

  

  CLAY-WORKING 
  

   Structure 
  of 
  clay 
  deposits 
  

  

  Eesidual 
  clays. 
  The 
  mode 
  of 
  origin 
  of 
  these 
  has 
  already 
  been 
  

   mentioned. 
  Such 
  a 
  clay 
  may 
  occur 
  either 
  in 
  the 
  form 
  of 
  a 
  broad 
  

   mantle 
  over 
  bed 
  rock, 
  of 
  variable 
  depth 
  and 
  lateral 
  extent, 
  or 
  it 
  

   may 
  occupy 
  the 
  position 
  of 
  a 
  vein 
  cutting 
  across 
  the 
  strike 
  of 
  the 
  

   other 
  rocks 
  or 
  sometimes 
  parallel 
  with 
  their 
  bedding 
  or 
  lamination. 
  

   Residual 
  clays 
  of 
  the 
  first 
  type 
  are 
  abundant 
  in 
  the 
  upland 
  regions 
  

   of 
  the 
  southern 
  states 
  and 
  form 
  the 
  most 
  abundant 
  brickmaking 
  

   material 
  of 
  that 
  part 
  of 
  the 
  country. 
  

  

  Residual 
  deposits 
  of 
  the 
  second 
  type 
  result 
  commonly 
  from 
  the 
  

   decomposition 
  of 
  veins 
  of 
  granite 
  or 
  feldspar. 
  They 
  vary 
  in 
  width 
  

   from 
  a 
  few 
  inches 
  to 
  several 
  hundred 
  feet. 
  Their 
  vertical 
  extent 
  

   depends 
  in 
  most 
  cases 
  on 
  the 
  depth 
  to 
  which 
  the 
  weathering 
  has 
  

   reached, 
  except 
  in 
  the 
  case 
  of 
  those 
  kaolin 
  deposits 
  which 
  have 
  re- 
  

   sulted 
  from 
  action 
  of 
  subterranean 
  vapors. 
  {See 
  " 
  Origin 
  of 
  clay,'' 
  

   p. 
  496) 
  Vein 
  formations 
  of 
  kaolin 
  seldom 
  show 
  great 
  length, 
  and 
  

   usually 
  pinch 
  out 
  in 
  both 
  directions. 
  In 
  some 
  localities 
  they 
  are 
  

   however 
  known 
  to 
  be 
  as 
  much 
  as 
  1000 
  feet 
  long. 
  They 
  are 
  com- 
  

   monly 
  separated 
  from 
  the 
  country 
  rock 
  by 
  more 
  or 
  less 
  sharp 
  

   boundaries, 
  which 
  are 
  preserved 
  even 
  though 
  the 
  wall 
  rock 
  also 
  be 
  

   decomposed, 
  as 
  it 
  usually 
  is. 
  They 
  frequently 
  branch, 
  and 
  at 
  times 
  

   contain 
  lenses 
  of 
  quartz, 
  which 
  resist 
  the 
  weathering 
  agencies 
  and 
  

   stand 
  out 
  in 
  bold 
  relief 
  on 
  the 
  surface. 
  It 
  rarely 
  pays 
  to 
  work 
  a 
  

   vein 
  under 
  6 
  feet 
  in 
  width. 
  

  

  Sedimentary 
  clays. 
  These 
  occur 
  in 
  the 
  form 
  of 
  beds 
  either 
  close 
  

   to 
  the 
  surface 
  or 
  interstratified 
  with 
  other 
  deposits 
  which 
  have 
  been 
  

   formed 
  by 
  water, 
  such 
  as 
  sandstones. 
  Deposits 
  of 
  sedimentary 
  

   clay 
  do 
  not 
  pass 
  gradually 
  into 
  the 
  underlying 
  rock 
  as 
  residual 
  

   clays 
  do. 
  In 
  many 
  parts 
  of 
  the 
  United 
  States 
  sedimentary' 
  clays 
  

   form 
  lens-shaped 
  masses 
  which 
  are 
  surrounded 
  on 
  all 
  side® 
  by 
  sand. 
  

   The 
  clay 
  beds 
  of 
  Staten 
  Island 
  weU 
  illustrate 
  this 
  point, 
  and 
  the 
  

   conditions 
  observed 
  are 
  caused 
  by 
  variations 
  in 
  the 
  velocity 
  of 
  the 
  

  

  