﻿HYDROLOGY 
  OF 
  NEW 
  YOfcPt 
  157 
  

  

  beneath 
  is 
  excluded 
  and 
  the 
  conditions 
  within 
  the 
  gage 
  are 
  differ- 
  

   ent 
  from 
  those 
  existing 
  in 
  outside 
  soil. 
  This 
  leads 
  to 
  the 
  earth 
  

   within 
  the 
  gage 
  becoming 
  abnormally 
  dry 
  in 
  times 
  of 
  drought, 
  and 
  

   on 
  the 
  advent 
  of 
  rain 
  absorbing 
  more 
  water 
  than 
  it 
  would 
  if 
  not 
  

   thus 
  isolated. 
  In 
  order 
  to 
  obviate 
  some 
  of 
  these 
  possible 
  diffi- 
  

   culties, 
  new 
  drain 
  gages 
  were 
  constructed 
  in 
  1888, 
  which 
  differ 
  

   from 
  the 
  preceding 
  gages 
  by 
  being 
  provided 
  with 
  an 
  artificial 
  

   water 
  table 
  which 
  is 
  kept 
  at 
  a 
  nearly 
  constant 
  hight 
  by 
  the 
  addi- 
  

   tion 
  of 
  sufficient 
  water, 
  daily, 
  to 
  make 
  up 
  the 
  loss 
  by 
  evaporation. 
  

  

  An 
  even 
  distribution 
  of 
  water 
  is 
  insured 
  by 
  a 
  layer 
  of 
  pebbles 
  

   placed 
  at 
  the 
  bottom 
  covered 
  with 
  another 
  of 
  clean 
  sand, 
  the 
  lat- 
  

   ter 
  reaching 
  up 
  far 
  enough 
  to 
  cover 
  the 
  drain 
  pipe. 
  The 
  soil 
  

   above, 
  while 
  not 
  directly 
  in 
  contact 
  with 
  water, 
  rests 
  upon 
  a 
  satu- 
  

   rated 
  layer 
  of 
  sand. 
  Four 
  drain 
  gages 
  were 
  constructed 
  on 
  the 
  

   new 
  plan 
  — 
  two 
  contain 
  a 
  column 
  of 
  soil 
  three 
  feet 
  in 
  depth, 
  ex- 
  

   clusive 
  of 
  the 
  sand 
  at 
  the 
  bottom, 
  while 
  the 
  other 
  two 
  contain 
  a 
  

   column 
  of 
  soil 
  six 
  feet 
  in 
  depth. 
  One 
  of 
  each 
  pair 
  was 
  filled 
  with 
  

   soil 
  in 
  place 
  in 
  order 
  to 
  preserve 
  its 
  natural 
  composition 
  and 
  

   solidity. 
  The 
  other 
  was 
  filled 
  with 
  air-dried 
  and 
  sifted 
  garden 
  

   soil. 
  Each 
  drain 
  gage 
  was 
  made 
  of 
  whiteoak 
  staves 
  of 
  equal 
  

   width, 
  cylindrical 
  in 
  form 
  and 
  lined 
  with 
  sheet 
  copper. 
  The 
  area 
  

   was 
  one 
  ten-thousandth 
  of 
  an 
  acre 
  as 
  before. 
  

  

  The 
  cylinders 
  filled 
  with 
  soil 
  in 
  place 
  were 
  sunk 
  about 
  the 
  col- 
  

   umns 
  of 
  soil 
  by 
  excavating 
  on 
  the 
  outside 
  and 
  dressing 
  down 
  the 
  

   column 
  to 
  fit 
  the 
  inside 
  of 
  the 
  cylinder. 
  The 
  cylinder 
  having 
  been 
  

   sunk 
  to 
  the 
  desired 
  depth 
  was 
  inclined 
  to 
  one 
  side 
  sufficiently 
  to 
  

   break 
  the 
  column 
  of 
  soil 
  at 
  the 
  lower 
  end, 
  when 
  the 
  plank 
  bottom 
  

   was 
  inserted 
  into 
  the 
  fissure 
  thus 
  formed. 
  After 
  various 
  manipu- 
  

   lations 
  which 
  it 
  is 
  not 
  necessary 
  to 
  describe, 
  the 
  cylinder 
  was 
  

   lifted 
  with 
  jackscrews 
  until 
  it 
  could 
  be 
  rolled 
  out 
  of 
  the 
  excava- 
  

   tion, 
  after 
  which 
  it 
  was 
  loaded 
  upon 
  a 
  wagon 
  and 
  hauled 
  to 
  the 
  

   pit 
  prepared 
  for 
  it, 
  where 
  it 
  was 
  unloaded, 
  with 
  the 
  end 
  intended 
  

   to 
  enter 
  the 
  soil 
  upward. 
  The 
  plank 
  (bottom 
  was 
  removed 
  and 
  six 
  

   inches 
  of 
  earth 
  taken 
  out 
  to 
  make 
  room 
  for 
  the 
  layer 
  of 
  sand 
  and 
  

   gravel 
  upon 
  which 
  the 
  column 
  of 
  soil 
  rests. 
  The 
  drain 
  tube 
  was 
  

   inserted, 
  soldered 
  to 
  place, 
  after 
  which 
  the 
  copper 
  bottom 
  was 
  

  

  