﻿PLEISTOCENE 
  GEOLOGY 
  OF 
  NASSAU 
  CO. 
  AND 
  BOROUGH 
  OF 
  QUEENS 
  655 
  

  

  In 
  the 
  southern 
  part 
  of 
  the 
  sand 
  plain 
  exposed 
  by 
  excava- 
  

   tion, 
  the 
  inclined, 
  or 
  fore 
  set 
  beds 
  are 
  not 
  overlain 
  by 
  any 
  distinct 
  

   coating 
  of 
  horizontal, 
  or 
  top 
  set 
  beds 
  but 
  farther 
  north 
  such 
  layers 
  

   appear. 
  {See 
  pi. 
  8) 
  

  

  The 
  bit 
  of 
  evidence 
  here 
  presented 
  concerning 
  the 
  form 
  of 
  the 
  ice 
  

   front 
  shows 
  that 
  the 
  margin 
  at 
  this 
  time 
  was 
  less 
  regular 
  than 
  when 
  

   it 
  lay 
  against 
  or 
  on 
  the 
  high 
  moraine 
  from 
  4 
  to 
  5 
  miles 
  south. 
  

   It 
  evidently 
  extended 
  across 
  Manhasset 
  bay 
  from 
  the 
  vicinity 
  of 
  

   Plum 
  point 
  to 
  the 
  opposite 
  sliore 
  and 
  thence 
  westward 
  lay 
  against 
  

   the 
  land 
  at 
  least 
  as 
  far 
  as 
  College 
  Point, 
  where 
  again 
  there 
  was 
  built 
  

   a 
  small 
  delta 
  deposit 
  later 
  than 
  the 
  moraine. 
  There 
  is 
  good 
  reason, 
  

   therefore, 
  to 
  believe 
  that 
  the 
  water 
  body 
  in 
  which 
  the 
  delta 
  at 
  Port 
  

   Washington 
  was 
  built 
  was 
  cut 
  off 
  from 
  the 
  sound 
  along 
  the 
  north 
  

   shore 
  of 
  the 
  island, 
  and 
  that 
  the 
  sound 
  was 
  as 
  yet 
  filled 
  with 
  glacial 
  

   ice. 
  Just 
  north 
  of 
  Port 
  Washington 
  village, 
  there 
  is 
  a 
  deep 
  channel 
  

   or 
  furrow 
  beginning 
  in 
  the 
  trough 
  occupied 
  by 
  the 
  middle 
  one 
  of 
  

   three 
  ponds 
  and 
  extending 
  northeastward 
  across 
  the 
  gravelly 
  and 
  till 
  

   deposit 
  to 
  the 
  vicinity 
  of 
  Mott 
  point. 
  The 
  bottom 
  of 
  this 
  trough, 
  

   whose 
  contours 
  are 
  shown 
  on 
  the 
  topographic 
  map, 
  is 
  about 
  75 
  feet 
  

   above 
  the 
  present 
  sealevel. 
  The 
  trough 
  has 
  the 
  form 
  of 
  one 
  of 
  

   those 
  creases 
  eroded 
  or 
  kept 
  open 
  by 
  water 
  flowing 
  out 
  of 
  the 
  ice 
  

   sheet 
  or 
  from 
  one 
  glacial 
  lake 
  to 
  another 
  along 
  the 
  ice 
  front. 
  At 
  

   the 
  time 
  it 
  may 
  have 
  connected 
  the 
  waters 
  confined 
  in 
  Hempstead 
  

   bay 
  with 
  the 
  water 
  held 
  by 
  the 
  ice 
  sheet 
  in 
  the 
  Manhasset 
  bay 
  

   depression. 
  

  

  The 
  crease 
  at 
  the 
  southern 
  end 
  of 
  Hempstead 
  bay, 
  at 
  Roslyn, 
  

   shows 
  clearly 
  that 
  a 
  stream 
  once 
  discharged 
  there 
  across 
  the 
  moraine 
  

   on 
  the 
  plain, 
  with 
  its 
  bed 
  over 
  120 
  feet 
  above 
  the 
  present 
  sealevel. 
  

   Hempstead 
  harbor 
  is 
  bounded 
  on 
  the 
  east 
  quite 
  up 
  to 
  the 
  sound 
  by 
  

   land 
  rising 
  above 
  100 
  feet, 
  so 
  that, 
  when 
  the 
  ice 
  front 
  retreated 
  from 
  

   the 
  morainal 
  wall 
  at 
  Poslyn, 
  drainage 
  would 
  continue 
  to 
  escape 
  

   through 
  the 
  Roslyn 
  channel 
  till 
  the 
  Mott 
  point 
  channel 
  was 
  opened 
  

   by 
  the 
  retreat 
  of 
  the 
  ice 
  north 
  of 
  that 
  point. 
  At 
  this 
  stage 
  any 
  open 
  

   water 
  in 
  Hempstead 
  harbor 
  would 
  have 
  escaped 
  into 
  the 
  Port 
  

   Washington 
  body 
  and 
  its 
  level 
  fallen 
  off 
  to 
  about 
  80 
  feet. 
  This 
  

   arrangement 
  of 
  cols 
  and 
  drainage 
  channels, 
  considered 
  in 
  relation 
  to 
  

   the 
  retreat 
  of 
  the 
  ice 
  front, 
  proved 
  by 
  the 
  Port 
  Washington 
  stage, 
  

  

  