﻿GEOLOGIC 
  F0EM1.TI0N8 
  OF 
  NEW 
  YORK 
  177 
  

  

  tance 
  and 
  dropped 
  to 
  form 
  the 
  flood 
  plains 
  and 
  terraces 
  which 
  

   border 
  our 
  river 
  valleys 
  and 
  the 
  hills 
  of 
  sand 
  and 
  gravel 
  in 
  the 
  

   valleys 
  which 
  are 
  called 
  kames 
  and 
  eskers. 
  Where 
  there 
  were 
  

   bodies 
  of 
  still 
  w^ater 
  the 
  finer 
  materials 
  were 
  dropped 
  to 
  form 
  

   clay. 
  

  

  At 
  this 
  time 
  the 
  country 
  was 
  deeply 
  submerged 
  and 
  tide 
  water 
  

   filled 
  the 
  valley 
  of 
  the 
  Hudson 
  river 
  and 
  Lake 
  Champlain 
  so 
  

   that 
  the 
  Gulf 
  of 
  St 
  Lawrence 
  and 
  New 
  York 
  harbor 
  were 
  united. 
  

   This 
  is 
  evidenced 
  by 
  the 
  fact 
  that 
  near 
  the 
  St 
  Lawrence 
  and 
  

   Lake 
  Champlain, 
  above 
  the 
  gravel 
  beds, 
  are 
  some 
  beds 
  of 
  clay 
  200 
  

   feet 
  thick 
  or 
  more, 
  which 
  contain 
  marine 
  shells 
  of 
  species 
  now 
  

   existing 
  on 
  the 
  coasts 
  of 
  New 
  England 
  and 
  Canada. 
  These 
  show 
  

   that, 
  since 
  such 
  shells 
  were 
  living, 
  those 
  valleys 
  have 
  been 
  de- 
  

   pressed 
  below 
  the 
  sea-level, 
  long 
  enough 
  for 
  these 
  deposits 
  of 
  clay 
  

   to 
  be 
  formed. 
  They 
  are 
  known 
  as 
  pleistocene 
  clays. 
  The 
  Hud- 
  

   son 
  river 
  valley 
  clays 
  are 
  their 
  southern 
  extension, 
  but 
  contain 
  no 
  

   fossils. 
  

  

  The 
  Quaternary 
  deposits 
  of 
  New 
  York 
  are, 
  therefore, 
  chiefly 
  

   those 
  made 
  in 
  the 
  presence 
  of 
  the 
  ice 
  and 
  those 
  resulting 
  from 
  

   the 
  working 
  over 
  of 
  the 
  glacial 
  deposits 
  by 
  running 
  water. 
  In 
  

   this 
  latter 
  process 
  the 
  angularity 
  of 
  the 
  glacial 
  boulders 
  and 
  

   pebbles 
  has 
  been 
  worn 
  off. 
  The 
  evidences 
  of 
  glacial 
  action 
  are 
  

   well 
  seen 
  in 
  almost 
  all 
  parts 
  of 
  this 
  state. 
  Almost 
  every 
  gravel- 
  

   bank 
  consists 
  of 
  waterworn 
  fragments 
  of 
  the 
  old 
  rocky 
  strata; 
  

   pebbles 
  of 
  limestone, 
  sandstone 
  and 
  slate, 
  with 
  some 
  of 
  gneiss 
  

   and 
  granite, 
  which 
  universally 
  appear 
  to 
  have 
  been 
  transported 
  

   from 
  north 
  to 
  south. 
  From 
  a 
  bushel 
  of 
  pebbles 
  taken 
  from 
  any 
  

   gravel 
  bank 
  south 
  of 
  the 
  Erie 
  canal, 
  the 
  geologist 
  can 
  pick 
  out 
  

   specimens 
  of 
  almost 
  every 
  stratum 
  which 
  is 
  exposed 
  north 
  of 
  the 
  

   bed 
  whence 
  they 
  were 
  taken. 
  South 
  of 
  the 
  line 
  of 
  outcrop 
  of 
  

   the 
  Helderberg 
  limestones, 
  the 
  gravels 
  are 
  full 
  of 
  fragments 
  of 
  

   their 
  different 
  layers; 
  and 
  among 
  them 
  lie 
  worn 
  pieces 
  of 
  the 
  

   red 
  Medina 
  sandstone, 
  others 
  of 
  the 
  Hudson 
  river 
  group, 
  and 
  

   others 
  of 
  still 
  more 
  northern 
  strata 
  ; 
  while 
  some 
  are 
  granite 
  peb- 
  

   bles, 
  which 
  must 
  in 
  many 
  instances 
  have 
  come 
  from 
  Canada. 
  

   They 
  have 
  evidently 
  been 
  transported 
  from 
  north 
  to 
  south 
  in 
  

  

  