﻿654 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  upper 
  surface, 
  as 
  indicated 
  by 
  the 
  topographic 
  map, 
  is 
  about 
  80 
  feet 
  

   above 
  the 
  present 
  sealevel. 
  The 
  outer, 
  or 
  southern 
  edge 
  of 
  this 
  

   delta 
  is 
  sliarplj 
  lobate, 
  each 
  lobe 
  corresponding, 
  as 
  in 
  existing 
  deltas, 
  

   to 
  the 
  end 
  of 
  some 
  distributary 
  stream 
  coursing 
  in 
  glacial 
  times 
  over 
  

   its 
  surface 
  to 
  the 
  body 
  of 
  water 
  in 
  which 
  the 
  deposit 
  was 
  accumu- 
  

   lating. 
  Taking 
  the 
  summit 
  line 
  of 
  these 
  lobes 
  as 
  indicating 
  the 
  water 
  

   level 
  of 
  the 
  time, 
  it 
  is 
  evident 
  that 
  the 
  water 
  body 
  rose 
  80 
  feet 
  above 
  

   the 
  present 
  sealevel. 
  We 
  shall 
  examine 
  presently 
  into 
  the 
  question 
  

   whether 
  this 
  water 
  was 
  the 
  sea 
  or 
  a 
  lake 
  held 
  in 
  on 
  the 
  north 
  side 
  of 
  

   the 
  moraine 
  by 
  the 
  ice 
  sheet 
  which 
  still 
  occupied 
  Long 
  Island 
  sound. 
  

  

  The 
  front 
  of 
  this 
  sand 
  plain 
  or 
  delta 
  is 
  concave 
  toward 
  Manhasset 
  

   bay, 
  trending 
  northward 
  from 
  Port 
  Washington 
  and 
  then 
  west- 
  

   ward 
  about 
  one 
  mile 
  beyond 
  the 
  village. 
  This 
  form 
  of 
  the 
  front 
  is 
  

   accordant 
  with 
  the 
  outline 
  of 
  the 
  outer 
  curve 
  of 
  the 
  neck. 
  At 
  a 
  

   distance 
  varying 
  from 
  half 
  a 
  mile 
  to 
  a 
  mile 
  from 
  the 
  lobes 
  the 
  glacial 
  

   stratified 
  sands 
  pass 
  into 
  till, 
  and 
  the 
  level 
  surface 
  of 
  the 
  old 
  delta 
  

   gives 
  place 
  to 
  a 
  huramocky 
  topography, 
  sloping 
  generally 
  toward 
  

   the 
  open 
  waters 
  of 
  the 
  sound, 
  plainly 
  indicating 
  the 
  deposits 
  which 
  

   were 
  laid 
  down 
  in 
  the 
  presence 
  of 
  the 
  ice 
  or 
  beneath 
  it 
  while 
  the 
  

   waters 
  pouring 
  from 
  the 
  ice 
  constructed 
  the 
  delta. 
  We 
  thus 
  have 
  

   the 
  picture 
  of 
  a 
  small 
  semicircular 
  embayment 
  of 
  the 
  ice 
  front. 
  

   From 
  an 
  inspection 
  of 
  the 
  ground, 
  it 
  appears 
  that 
  the 
  edge 
  of 
  the 
  

   ice 
  lapped 
  over 
  on 
  the 
  existing 
  land 
  for 
  a 
  distance 
  of 
  three 
  fourths 
  

   of 
  a 
  mile 
  to 
  nearly 
  a 
  mile 
  from 
  Barker 
  point, 
  around 
  by 
  Sands 
  Light 
  

   point, 
  and 
  for 
  a 
  slightly 
  greater 
  breadth 
  on 
  the 
  eastern 
  side, 
  at 
  

   least 
  as 
  far 
  as 
  Mott 
  point. 
  Beyond 
  this 
  locality 
  it 
  is 
  quite 
  impossible 
  

   to 
  discriminate 
  the 
  deposits 
  of 
  the 
  ice 
  made 
  at 
  this 
  stage 
  from 
  the 
  

   earlier 
  deposits 
  laid 
  down 
  when 
  the 
  ice 
  front 
  was 
  closely 
  pressed 
  

   against 
  the 
  moraine 
  on 
  the 
  south. 
  

  

  The 
  structure 
  of 
  the 
  delta 
  as 
  exposed 
  in 
  the 
  summer 
  of 
  1900 
  is 
  

   typically 
  deltiform, 
  with 
  beds 
  of 
  sand 
  steeply 
  inclined 
  toward 
  the 
  

   frontal 
  lobes, 
  each 
  bed 
  having 
  been 
  deposited 
  in 
  its 
  present 
  inclina- 
  

   tion 
  on 
  the 
  growing 
  edge 
  of 
  the 
  delta, 
  as 
  the 
  streams 
  coursing 
  over 
  

   the 
  embankment, 
  already 
  built 
  up 
  to 
  water 
  level 
  by 
  this 
  process, 
  

   came 
  to 
  the 
  outer 
  margin 
  and 
  let 
  their 
  load 
  of 
  sand 
  come 
  to 
  rest 
  

   by 
  sliding 
  down 
  the 
  frontal 
  slope 
  to 
  the 
  angle 
  of 
  repose 
  for 
  that 
  

   material 
  in 
  water. 
  {See 
  pi. 
  Y 
  and 
  8) 
  

  

  