﻿158 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  older 
  beds 
  of 
  somewhat 
  different 
  quality, 
  more 
  or 
  less 
  crushed 
  by 
  

   overriding 
  of 
  the 
  ice; 
  and 
  tills 
  interbedded 
  between 
  the 
  older 
  and 
  

   the 
  newer 
  clays. 
  No 
  such 
  features 
  have 
  been 
  seen. 
  In 
  the 
  few 
  

   sections 
  observed 
  reaching 
  to 
  rock 
  the 
  clay 
  reposes 
  directly 
  on 
  the 
  

   smoothed 
  rock, 
  and 
  the 
  deposit 
  is 
  similar 
  and 
  homogeneous 
  from 
  

   bottom 
  upward, 
  and 
  very 
  finely 
  laminated. 
  The 
  cases 
  of 
  crump- 
  

   ling 
  which 
  have 
  been 
  noted 
  are 
  probably 
  explicable 
  by 
  the 
  ground- 
  

   ing 
  of 
  icebergs, 
  or 
  perhaps 
  by 
  the 
  thrust 
  of 
  the 
  accumulating 
  weight 
  

   of 
  clay 
  on 
  weaker 
  borders 
  of 
  the 
  deposit. 
  

  

  An 
  explanation 
  of 
  the 
  large 
  volume 
  and 
  extent 
  of 
  the 
  clay 
  seems 
  

   to 
  lie 
  in 
  the 
  consideration 
  of 
  the 
  lake 
  conditions 
  at 
  the 
  front 
  of 
  

   the 
  waning 
  ice 
  sheet 
  and 
  the 
  mechanical 
  factors 
  working 
  there. 
  

   In 
  ordinary 
  glacial 
  drift 
  or 
  till 
  the 
  coarse 
  materials 
  remain 
  in 
  mix- 
  

   ture 
  with 
  the 
  clay 
  (rock 
  flour) 
  matrix. 
  But 
  the 
  agitated 
  deep 
  

   water 
  in 
  which 
  all 
  the 
  deposits 
  of 
  our 
  area 
  have 
  been 
  laid 
  down 
  

   have 
  screened 
  out 
  the 
  coarse 
  from 
  the 
  fine, 
  dropping 
  the 
  coarse 
  

   near 
  the 
  ice 
  front, 
  and 
  have 
  carried 
  the 
  fine 
  material 
  away 
  by 
  itself 
  

   farther 
  from 
  the 
  ice 
  front 
  into 
  the 
  more 
  quiet 
  water. 
  It 
  should 
  

   be 
  understood 
  that 
  the 
  deposits 
  as 
  a 
  whole 
  were 
  accumulated 
  from 
  

   south 
  to 
  north, 
  following 
  the 
  departing 
  ice 
  front. 
  In 
  other 
  words 
  

   they 
  grew 
  backward. 
  It 
  is 
  possible 
  that 
  either 
  by 
  lifting 
  or 
  by 
  

   toppling 
  the 
  breaking 
  ice 
  kept 
  the 
  water 
  agitated 
  and 
  so 
  facilitated 
  

   its 
  sifting 
  action. 
  The 
  materials 
  contributed 
  by 
  the 
  glacial 
  streams 
  

   were 
  already 
  under 
  assorting 
  action. 
  Lack 
  of 
  strong, 
  continuous 
  

   currents, 
  as 
  rivers, 
  or 
  as 
  in 
  tidal 
  seas, 
  prevented 
  the 
  far 
  removal 
  of 
  

   the 
  silt, 
  and 
  the 
  muddy 
  waters 
  dropped 
  their 
  clay 
  burden 
  over 
  the 
  

   bottom 
  not 
  far 
  in 
  advance 
  of 
  the 
  ice 
  front. 
  Subsequently 
  the 
  low- 
  

   ering 
  waters 
  scraped 
  the 
  silt 
  which 
  had 
  been 
  dropped 
  on 
  the 
  higher 
  

   surfaces 
  down 
  into 
  the 
  lower 
  grounds 
  and 
  hollows. 
  As 
  there 
  was 
  no 
  

   break 
  in 
  the 
  existence 
  of 
  the 
  standing 
  and 
  lowering 
  waters, 
  and 
  

   consequently 
  no 
  pause 
  in 
  the 
  depositional 
  process, 
  so 
  we 
  find 
  con- 
  

   tinuity 
  and 
  uniformity 
  in 
  the 
  deposits. 
  

  

  Pitted 
  clays. 
  In 
  the 
  hollows 
  or 
  basins 
  of 
  the 
  Alexandria 
  Bay 
  dis- 
  

   trict 
  [pi. 
  47] 
  are 
  found 
  deposits 
  of 
  clay 
  which 
  are 
  pitted 
  with 
  

   basins 
  or 
  kettles. 
  In 
  some 
  instances 
  the 
  silt 
  forms 
  merely 
  mounds 
  

   and 
  ridges 
  with 
  intervening 
  swales 
  and 
  swamps, 
  a 
  good 
  example 
  

   being 
  seen 
  3 
  miles 
  north 
  of 
  Redwood. 
  

  

  These 
  pitted 
  clay 
  fillings 
  blend 
  on 
  the 
  one 
  hand 
  into 
  till, 
  and 
  on 
  

   the 
  other 
  into 
  the 
  smooth 
  or 
  merely 
  eroded 
  clay 
  plains. 
  The 
  ex- 
  

   planation 
  of 
  their 
  origin 
  seems 
  to 
  be 
  the 
  deposition 
  of 
  the 
  silts 
  over 
  

   grounded 
  ice 
  or 
  anchored 
  ice 
  blocks. 
  Apparently 
  the 
  ice 
  masses 
  

   were 
  not 
  melted 
  until 
  the 
  silt 
  deposition 
  was 
  ended. 
  

  

  