﻿CLAYS 
  OF 
  XEW 
  YOEK 
  501 
  

  

  and, 
  if 
  tlie 
  deposit 
  is 
  found 
  in 
  the 
  locality 
  where 
  it 
  was 
  formed, 
  

   it 
  is 
  known 
  as 
  a 
  residual 
  clay. 
  

  

  Clay 
  may 
  also 
  be 
  derived 
  from 
  the 
  decomposition 
  of 
  aluminous 
  

   limestones. 
  

  

  Deposits 
  of 
  kaolin 
  are 
  not 
  very 
  common, 
  but 
  residual 
  clays 
  ara 
  

   Indeed 
  in 
  many 
  of 
  the 
  southern 
  states 
  the 
  surfac-e 
  soil 
  over 
  many 
  

   square 
  miles 
  is 
  nothing 
  more 
  than 
  a 
  residual 
  clay. 
  Such 
  residual 
  

   deposits 
  often 
  bear 
  a 
  close 
  resemblance 
  in 
  chemical 
  composition, 
  

   to 
  the 
  rock 
  from 
  which 
  they 
  were 
  formed. 
  

  

  Under 
  the 
  influence 
  of 
  weathering 
  the 
  residual 
  surface 
  materials 
  

   are 
  washed 
  down 
  into 
  the 
  rivers 
  and 
  carried 
  to 
  seas 
  or 
  lakes 
  

   where 
  they 
  are 
  spread 
  out 
  over 
  the 
  bottom 
  as 
  sediments. 
  We 
  

   thus 
  have 
  another 
  class 
  of 
  clay 
  deposits 
  known 
  as 
  sedimentary 
  

   clay, 
  no 
  longer 
  resembling 
  the 
  parent 
  rock, 
  but 
  composed 
  of 
  the 
  

   residuum 
  of 
  several 
  different 
  areas. 
  

  

  These 
  two 
  types 
  of 
  clay 
  deposits, 
  the 
  residual 
  and 
  the 
  sedi/- 
  

   mentary, 
  present 
  certain 
  distinguishable 
  features, 
  bearing 
  on 
  their 
  

   origin. 
  

  

  Residual 
  clays 
  are 
  composed 
  of 
  a 
  mixture 
  of 
  angular 
  grains 
  rep- 
  

   resenting 
  in 
  part 
  undecomposed 
  rock, 
  and 
  fine 
  rock 
  flour 
  of 
  clay, 
  

   that 
  is, 
  particles 
  sufficiently 
  flne 
  to 
  float 
  in 
  water. 
  There 
  is 
  generally 
  

   a 
  gradual 
  transition 
  from 
  the 
  fully 
  formed 
  clay 
  at 
  the 
  surface 
  to 
  

   the 
  unaltered 
  parent 
  rock 
  below. 
  The 
  depth 
  below 
  the 
  surface 
  

   at 
  which 
  unaltered 
  rock 
  is 
  reached 
  varies 
  from 
  three 
  or 
  four 
  feet 
  

   to 
  150 
  or 
  200 
  feet. 
  The 
  structure 
  of 
  the 
  parent 
  rock 
  is 
  sometimes 
  

   retained 
  for 
  a 
  certain 
  distance 
  upward 
  in 
  the 
  residual 
  clay. 
  

  

  Sedimentary 
  clays 
  are 
  stratified 
  and 
  occur 
  in 
  beds. 
  They 
  are 
  

   as 
  a 
  rule 
  more 
  homogeneous 
  than 
  residual 
  clays 
  and 
  contain 
  a 
  

   greater 
  proportion 
  of 
  fine 
  particles. 
  They 
  are 
  also 
  more 
  plastic, 
  

   and 
  frequently 
  have 
  much 
  . 
  disseminated 
  organic 
  matter, 
  but 
  tliey 
  

   bear 
  little 
  or 
  no 
  relation 
  to 
  the 
  rocks 
  on 
  which 
  they 
  rest. 
  

  

  Sedimentary 
  clays 
  occur 
  either 
  at 
  the 
  surface, 
  or 
  may 
  lie 
  deep 
  

   below 
  it, 
  interbedded 
  with 
  other 
  rocks. 
  

  

  When 
  sedimentary 
  clays 
  suffer 
  consolidation 
  under 
  pressure 
  they 
  

  

  