﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  713 
  

  

  be 
  covered 
  by 
  the 
  terminal 
  moraine 
  of 
  the 
  continental 
  glacier, 
  

   with 
  surface 
  formation 
  very 
  impervious. 
  The 
  conditions, 
  there- 
  

   fore, 
  are 
  quite 
  different 
  here 
  from 
  Long 
  Island, 
  where 
  extensive 
  

   areas 
  of 
  coarse 
  sand 
  permit 
  a 
  large 
  proportion 
  of 
  the 
  rainfall 
  

   to 
  sink 
  into 
  the 
  earth. 
  Moreover, 
  the 
  geologic 
  structure 
  is 
  

   such 
  as 
  to 
  render 
  it 
  improbable 
  that 
  any 
  such 
  large 
  amount 
  of 
  

   ground 
  water 
  can 
  be 
  obtained 
  as 
  in 
  the 
  adjacent 
  area 
  of 
  New 
  

   Jersey. 
  

  

  The 
  geology 
  of 
  Staten 
  Island 
  has 
  been 
  reported 
  upon 
  by 
  Pro- 
  

   fessor 
  W. 
  O. 
  Crosby 
  of 
  the 
  Massachusetts 
  Institute 
  of 
  Technology. 
  

   In 
  this 
  report 
  it 
  is 
  stated 
  that 
  borings 
  in 
  the 
  vicinity 
  of 
  Wood- 
  

   bridge 
  and 
  Perth 
  Amboy 
  show 
  that 
  the 
  traprock 
  and 
  the 
  ridge 
  

   of 
  crystalline 
  rocks 
  are 
  continued 
  only 
  at 
  moderate 
  depths 
  below 
  

   the 
  surface, 
  and 
  that 
  in 
  consequence 
  the 
  cretaceous 
  strata 
  under- 
  

   lying 
  the 
  entire 
  lowlands 
  south 
  of 
  the 
  serpentine 
  ridge, 
  and 
  which 
  

   in 
  New 
  Jersey 
  embrace 
  several 
  good 
  water 
  horizons, 
  are 
  cut 
  off 
  

   from 
  the 
  catchment 
  areas 
  either 
  on 
  the 
  mainland 
  or 
  on 
  the 
  

   northern 
  part 
  of 
  Staten 
  Island. 
  Moreover, 
  the 
  fact 
  that 
  the 
  wells 
  

   penetrating 
  the 
  cretaceous 
  strata 
  are 
  practical 
  failures 
  indicates 
  

   that 
  the 
  water-bearing 
  strata 
  outcrop 
  on 
  this 
  island 
  only 
  to 
  a 
  

   very 
  limited 
  extent 
  or 
  not 
  at 
  all. 
  

  

  The 
  gray 
  gravel 
  and 
  blue 
  gray 
  formations 
  of 
  Long 
  Island 
  are, 
  

   so 
  far 
  as 
  can 
  be 
  observed, 
  wholly 
  wanting 
  on 
  Staten 
  Island, 
  and 
  

   the 
  yellow 
  gravel, 
  which 
  is 
  an 
  important 
  reservoir 
  of 
  ground 
  

   water 
  on 
  Long 
  Island, 
  has 
  only 
  a 
  limited 
  development 
  on 
  Staten 
  

   Island, 
  being 
  practically 
  confined 
  to 
  the 
  cretaceous 
  lowlands, 
  

   which 
  are 
  the 
  source 
  of 
  such 
  wells 
  as 
  are 
  not 
  failures. 
  

  

  Moreover, 
  the 
  greater 
  portion 
  of 
  the 
  area 
  of 
  Staten 
  Island 
  

   is 
  covered 
  by 
  bowlder 
  clay, 
  which 
  is 
  of 
  an 
  exceptionally 
  imper- 
  

   vious 
  character, 
  as 
  proved 
  by 
  numerous 
  ponds 
  more 
  or 
  less 
  

   effectually 
  sealing 
  the 
  catchment 
  areas 
  of 
  strata 
  which 
  might 
  

   otherwise 
  be 
  water-bearing. 
  The 
  bowlder 
  clay 
  is 
  in 
  many 
  places 
  

   from 
  50 
  feet 
  to 
  200 
  feet 
  thick. 
  

  

  To 
  summarize, 
  the 
  geologic 
  conditions 
  affecting 
  the 
  storage 
  

   and 
  flow 
  of 
  ground 
  water 
  are 
  generally 
  unfavorable, 
  because 
  all 
  

   the 
  formations, 
  excepting 
  the 
  yellow 
  gravel, 
  are 
  naturally 
  of 
  little 
  

   value 
  as 
  sources 
  of 
  ground 
  water. 
  Unfortunately, 
  the 
  yellow 
  

   gravel 
  has 
  not 
  only 
  a 
  limited 
  catchment 
  area, 
  but 
  the 
  small 
  areas 
  

  

  