﻿636 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Long 
  Island 
  sound. 
  The 
  inference 
  is 
  that 
  at 
  a 
  time 
  immediately 
  

   before 
  the 
  last 
  advance 
  of 
  the 
  ice 
  the 
  area 
  was 
  exposed 
  to 
  ordinary 
  

   stream 
  action 
  opening 
  out 
  valleys 
  on 
  the 
  gravels 
  and 
  sands, 
  the 
  

   mouths 
  of 
  these 
  streams 
  reaching 
  the 
  sea 
  below 
  the 
  present 
  sealevel. 
  

  

  There 
  are 
  other 
  evidences, 
  however, 
  which 
  show 
  that 
  ice 
  action 
  

   has 
  considerably 
  modified 
  and 
  enlarged 
  certain 
  of 
  these 
  valleys. 
  

   Such 
  enlarged 
  valleys 
  constitute 
  the 
  bays 
  and 
  harbors 
  of 
  the 
  north 
  

   shore. 
  These 
  harbors 
  have 
  their 
  bottoms 
  27 
  feet 
  below 
  sealevel 
  in 
  

   Hem]:)stead 
  bay, 
  61 
  feet 
  in 
  Oyster 
  bay 
  and 
  33 
  feet 
  in 
  Manhasset 
  

   bay. 
  This 
  depth 
  in 
  each 
  case 
  is 
  probably 
  less 
  than 
  the 
  original 
  depth 
  

   of 
  the 
  depressions, 
  for 
  there 
  has 
  been 
  some 
  infilling 
  by 
  glacial 
  

   deposition 
  — 
  probably 
  small 
  as 
  judged 
  by 
  the 
  filling 
  in 
  of 
  valleys 
  

   extending 
  above 
  sealevel 
  ^ 
  — 
  and 
  some 
  infilling 
  through 
  post-glacial 
  

   deposition 
  by 
  tides 
  and 
  currents. 
  Arguments 
  for 
  the 
  excavation 
  of 
  

   these 
  embayments 
  subsequent 
  to 
  the 
  formation 
  of 
  the 
  Columbia 
  

   gravels 
  and 
  sands 
  have 
  already 
  been 
  given 
  on 
  p. 
  628. 
  Homologous 
  

   depressions 
  occur 
  eastward 
  on 
  this 
  island 
  in 
  Coldspring 
  and 
  North- 
  

   port 
  harbors. 
  They 
  are 
  also 
  found 
  on 
  Marthas 
  Vineyard 
  in 
  Lagoon 
  

   pond 
  and 
  Menemsha 
  pond, 
  and 
  on 
  Block 
  island 
  in 
  Great 
  pond. 
  

  

  As 
  to 
  the 
  period 
  of 
  this 
  valley-making, 
  excepting 
  the 
  modification 
  

   and 
  enlargement 
  by 
  ice 
  action, 
  it 
  is 
  clearly 
  older 
  than 
  the 
  main 
  

   or 
  inner 
  moraine 
  at 
  Koslyn, 
  a 
  deposit 
  believed 
  to 
  be 
  equivalent 
  to 
  

   the 
  Cape 
  Cod 
  moraine. 
  Whether 
  the 
  stream 
  erosion 
  preceded 
  or 
  

   followed 
  those 
  fragments 
  of 
  an 
  older 
  moraine 
  which 
  on 
  this 
  sheet 
  

   mark 
  the 
  western 
  extension 
  of 
  the 
  outer 
  or 
  I^antucket 
  moraine, 
  

   appears 
  to 
  be 
  locally 
  undeterminable, 
  because 
  the 
  two 
  sets 
  of 
  phe- 
  

   nomena 
  are 
  not 
  found 
  in 
  association. 
  If 
  a 
  comparison 
  w^ith 
  Marthas 
  

   Yineyard 
  and 
  Block 
  island 
  holds 
  good, 
  the 
  erosion 
  of 
  the 
  valleys 
  

   should 
  be 
  here 
  as 
  there 
  anterior 
  to 
  both 
  moraines. 
  In 
  all 
  of 
  these 
  

   New 
  England 
  islands, 
  the 
  valleys 
  do 
  not 
  occur 
  as 
  such 
  on 
  the 
  south 
  

   of 
  the 
  moraines, 
  because 
  that 
  area 
  has 
  been 
  buried 
  beneath 
  the 
  out- 
  

   wash 
  plains 
  of 
  the 
  first 
  or 
  outer 
  moraine 
  on 
  the 
  eastern 
  islands 
  and 
  

   of 
  both 
  the 
  first 
  and 
  second, 
  or 
  inner 
  and 
  outer 
  moraine 
  on 
  Long 
  

   Island. 
  

  

  The 
  time 
  involved 
  in 
  the 
  excavation 
  of 
  these 
  valleys 
  is 
  indetermi- 
  

   nate. 
  They 
  are 
  largely 
  excavated 
  in 
  gravels 
  and 
  sands 
  of 
  a 
  porous 
  

   structure. 
  Much 
  of 
  the 
  existing 
  rainfall 
  passes 
  through 
  the 
  

  

  