﻿684 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  island. 
  The 
  highest 
  points 
  of 
  this 
  ridge 
  are 
  about 
  350 
  to 
  390 
  

   feet 
  above 
  sea 
  level. 
  This 
  ridge, 
  which 
  is 
  believed 
  to 
  be 
  a 
  part 
  

   of 
  the 
  terminal 
  moraine 
  of 
  the 
  great 
  glacier, 
  consists 
  mainly 
  

   of 
  compact 
  drift 
  and 
  bowlders, 
  running 
  at 
  times 
  into 
  clay 
  and 
  

   coarse 
  gravel. 
  The 
  considerable 
  number 
  of 
  small 
  ponds 
  along 
  

   the 
  ridge 
  evidence 
  the 
  compactness 
  of 
  its 
  surface 
  material. 
  The 
  

   slopes 
  and 
  spurs 
  of 
  the 
  central 
  ridge 
  run 
  into 
  Long 
  Island 
  

   sound 
  on 
  the 
  north, 
  making 
  an 
  irregular 
  shore 
  line, 
  broken 
  

   into 
  bays 
  and 
  Ioav 
  head 
  lands. 
  On 
  the 
  south 
  side, 
  the 
  slopes 
  

   lose 
  themselves 
  in 
  a 
  grassy 
  plain 
  sloping 
  gently 
  toward 
  the 
  

   coast. 
  In 
  its 
  widest 
  part 
  it 
  is 
  called 
  the 
  Hempstead 
  plains, 
  and 
  

   stretches 
  for 
  a 
  distance 
  of 
  from 
  5 
  to 
  15 
  miles 
  between 
  the 
  foot 
  

   of 
  the 
  central 
  ridge 
  and 
  the 
  Atlantic 
  shore, 
  which 
  is 
  very 
  regu- 
  

   lar 
  in 
  its 
  outer 
  beacn 
  line; 
  but 
  an 
  inner 
  and 
  more 
  irregular 
  

   beach 
  exists, 
  formed 
  by 
  the 
  shallow 
  waters 
  of 
  Jamaica 
  and 
  

   Hempstead 
  bays. 
  The 
  Atlantic 
  shore 
  does 
  not 
  anywhere 
  touch 
  

   the 
  slope 
  of 
  the 
  central 
  ridge, 
  but 
  is 
  separated 
  from 
  it 
  by 
  the 
  

   wide 
  gravelly 
  plain. 
  

  

  In 
  1900 
  Prof. 
  W. 
  O. 
  Crosby 
  reported 
  in 
  relation 
  to 
  the 
  geology 
  

   of 
  Long 
  Island 
  and 
  its 
  relations 
  to 
  public 
  water 
  supplies, 
  the 
  

   main 
  purpose 
  of 
  this 
  study 
  being 
  to 
  determine 
  what 
  light 
  the 
  

   present 
  knowledge 
  of 
  the 
  geologic 
  structure 
  of 
  Long 
  Island 
  

   throws 
  upon 
  these 
  problems. 
  The 
  main 
  questions 
  considered 
  

   were: 
  

  

  1) 
  Is 
  it 
  possible 
  to 
  obtain 
  a 
  copious 
  supply 
  of 
  water 
  from 
  

   deep 
  wells 
  on 
  Long 
  Island, 
  200 
  feet 
  or 
  more 
  in 
  depth, 
  passing- 
  

   through 
  the 
  blue 
  clay 
  into 
  the 
  gray 
  gravel 
  and 
  the 
  still 
  deeper 
  

   water-bearing 
  strata 
  of 
  the 
  cretaceous? 
  A 
  supply 
  of 
  quality 
  

   suitable 
  for 
  domestic 
  purposes 
  and 
  in 
  quantity 
  sufficient 
  for 
  a 
  

   substantial 
  addition 
  to 
  Brooklyn's 
  water 
  supply, 
  say 
  10,000,000 
  

   gallons, 
  25,000,000 
  gallons, 
  50,000,000 
  gallons, 
  or 
  more 
  per 
  day, 
  

   or 
  the 
  equivalent 
  of 
  the 
  yield 
  of 
  a 
  catchment 
  area 
  of 
  10, 
  25, 
  50 
  

   or 
  more 
  square 
  miles? 
  

  

  2) 
  What 
  certainty 
  or 
  probability 
  is 
  there 
  that 
  wells 
  40 
  to 
  

   80 
  feet 
  deep, 
  sunk 
  in 
  the 
  yellow 
  gravel 
  but 
  not 
  penetrating 
  the 
  

   blue 
  clay, 
  in 
  the 
  region 
  east 
  of 
  Massapequa, 
  can 
  be 
  made 
  to 
  

   yield 
  water 
  of 
  suitable 
  quality 
  for 
  domestic 
  supply 
  and 
  in 
  quan- 
  

   tity 
  equal 
  to 
  the 
  total 
  average 
  catch 
  of 
  rainfall 
  on 
  a 
  catch- 
  

  

  