﻿CLAYS 
  OF 
  NEW 
  YOEK 
  577 
  

  

  The 
  clay 
  is 
  chiefly 
  blue, 
  but 
  where 
  the 
  overlying 
  sand 
  is 
  wanting 
  

   or 
  is 
  of 
  slight 
  thickness, 
  it 
  is 
  weathered 
  to 
  yellow, 
  this 
  weather- 
  

   ing 
  often 
  extending 
  to 
  a 
  depth 
  of 
  15 
  feet 
  below 
  the 
  surface, 
  and 
  

   to 
  a 
  still 
  greater 
  depth 
  along 
  the 
  line 
  of 
  fissures 
  through 
  which 
  

   the 
  water 
  can 
  percolate. 
  The 
  depth 
  of 
  oxidation 
  is 
  of 
  course 
  influ- 
  

   enced 
  by 
  the 
  nature 
  of 
  the 
  clay, 
  the 
  upper 
  portion 
  weathering 
  

   easily 
  on 
  account 
  of 
  its 
  more 
  sandy 
  nature 
  and 
  hence 
  looser 
  text- 
  

   ure. 
  Horizontal 
  stratification 
  is 
  marked 
  and 
  the 
  layers 
  of 
  clay 
  

   are 
  separated 
  by 
  extremely 
  thin 
  laminae 
  of 
  sand. 
  At 
  some 
  locali- 
  

   ties 
  the 
  layers 
  of 
  the 
  clay 
  are 
  very 
  thin 
  and 
  alternate 
  with 
  equally 
  

   thin 
  layers 
  of 
  sandy 
  clay. 
  This 
  condition 
  is 
  found 
  at 
  Haverstraw, 
  

   Croton, 
  Dutchess 
  Junction, 
  Stonypoint, 
  Fishkill, 
  Cornwall, 
  ISTew 
  

   Windsor, 
  Catskill 
  and 
  Port 
  Ewen. 
  At 
  all 
  of 
  the 
  above 
  mentioned 
  

   localities 
  except 
  the 
  last 
  two, 
  the 
  clay 
  is 
  overlain 
  by 
  the 
  delta 
  de- 
  

   posits 
  of 
  rivers 
  tributary 
  to 
  the 
  Hudson, 
  and 
  the 
  alternation 
  of 
  

   layers 
  may 
  be 
  due 
  to 
  variations 
  in 
  the 
  flow 
  of 
  the 
  rivers 
  emptying 
  

   at 
  those 
  points, 
  the 
  sandy 
  layers 
  being 
  deposited 
  during 
  period 
  of 
  

   floods. 
  The 
  delta 
  of 
  Catskill 
  creek 
  has 
  been 
  found 
  at 
  Leeds, 
  some 
  

   2 
  miles 
  west 
  of 
  the 
  Hudson 
  river. 
  ^ 
  The 
  delta 
  of 
  Rondout 
  creek, 
  

   which 
  flows 
  into 
  the 
  Hudson 
  at 
  Port 
  Ewen, 
  will 
  no 
  doubt 
  be 
  

   found 
  by 
  following 
  the 
  creek 
  back 
  to 
  the 
  ancient 
  shore 
  line 
  of 
  the 
  

   Hudson 
  estuary. 
  Isolated 
  ice-scratched 
  boulders 
  are 
  not 
  uncom- 
  

   monly 
  found 
  in 
  the 
  clay. 
  

  

  There 
  is 
  often 
  a 
  sharp 
  line 
  of 
  division 
  between 
  the 
  yellow 
  

   weathered 
  portion 
  and 
  the 
  blue 
  or 
  unweathered 
  part 
  of 
  the 
  clay. 
  

   The 
  line 
  of 
  separation 
  between 
  the 
  clay 
  and 
  overlying 
  sand 
  is 
  also 
  

   quite 
  distinct 
  in 
  most 
  cases. 
  Of 
  the 
  blue 
  and 
  the 
  yellow 
  clay 
  the 
  

   former 
  is 
  the 
  more 
  plastic, 
  but 
  both 
  effervesce 
  readily 
  with 
  acid 
  due 
  

   to 
  the 
  presence 
  of 
  3^-6^ 
  of 
  carbonate 
  of 
  lime, 
  and 
  are 
  therefore, 
  

   properly 
  speaking, 
  marly 
  clays. 
  The 
  clay 
  is 
  underlain 
  by 
  a 
  bed 
  

   of 
  gravel, 
  sand, 
  hardpan, 
  boulder, 
  till 
  or 
  bed 
  rock. 
  From 
  Albany 
  

   to 
  Catskill 
  the 
  underlying 
  material 
  is 
  a 
  dark 
  gray 
  or 
  black 
  sand 
  

  

  1 
  W. 
  M. 
  Davis. 
  Proc. 
  Bost. 
  soc. 
  nat. 
  hist. 
  Nov. 
  1892. 
  

  

  