﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  85 
  

  

  These 
  gages 
  were 
  located 
  at 
  Chestnut 
  Hill 
  reservoir, 
  in 
  the 
  city 
  

   of 
  Boston, 
  but 
  the 
  observations 
  for 
  wind 
  velocity 
  were 
  taken 
  from 
  

   the 
  Signal 
  Service 
  observations, 
  5 
  miles 
  distant. 
  With 
  only 
  five 
  

   exceptions 
  during 
  the 
  five-year 
  period, 
  the 
  upper 
  gage 
  delivered 
  

   materially 
  less 
  water 
  than 
  the 
  ground 
  gage, 
  the 
  average 
  difference 
  

   being 
  10.6 
  per 
  cent 
  for 
  the 
  whole 
  period. 
  But 
  snowfalls 
  and 
  

   mixtures 
  of 
  snow 
  and 
  rain 
  are 
  not 
  included 
  in 
  the 
  table 
  of 
  data 
  

   given 
  in 
  the 
  paper. 
  

  

  The 
  results 
  recorded 
  by 
  Professor 
  Abbe 
  are 
  somewhat 
  more 
  

   extensive 
  than 
  those 
  presented 
  by 
  Mr 
  FitzGerald, 
  though 
  Mr 
  

   FitzGerald 
  states 
  in 
  his 
  paper 
  that 
  he 
  has 
  prepared 
  a 
  series 
  of 
  

   experiments 
  with 
  nine 
  gages 
  and 
  a 
  self-recording 
  anemometor, 
  

   from 
  which 
  in 
  the 
  course 
  of 
  time 
  some 
  more 
  definite 
  results 
  may 
  

   be 
  reached. 
  So 
  far 
  as 
  the 
  writer 
  knows, 
  this 
  second 
  series 
  of 
  

   observations 
  has 
  not 
  been 
  published. 
  

  

  In 
  order 
  to 
  show 
  how 
  the 
  catch 
  of 
  rainfall 
  diminishes 
  with 
  

   hight 
  of 
  the 
  gage, 
  Professor 
  Abbe 
  gives 
  in 
  his 
  table 
  No. 
  IV 
  the 
  

   results 
  of 
  observations 
  at 
  different 
  places. 
  These 
  range 
  from 
  90 
  

   per 
  cent 
  of 
  a 
  gage 
  at 
  the 
  ground 
  to 
  47 
  per 
  cent. 
  In 
  tables 
  Nos. 
  

   I, 
  II, 
  and 
  III, 
  Professor 
  Abbe 
  also 
  gives 
  the 
  result 
  of 
  various 
  

   gages, 
  which 
  gave 
  52 
  to 
  7 
  per 
  cent 
  less 
  of 
  rainfall, 
  and 
  from 
  80 
  to 
  

   16 
  per 
  cent 
  less 
  of 
  snowfall, 
  than 
  gages 
  at 
  the 
  ground. 
  Professor 
  

   Abbe 
  remarks 
  that 
  these 
  tables 
  show 
  conclusively 
  the 
  large 
  

   influence 
  of 
  wind 
  on 
  the 
  catch 
  of 
  rain, 
  but 
  show 
  nothing 
  of 
  its 
  

   influence 
  on 
  the 
  catch 
  of 
  snow. 
  As 
  an 
  observational 
  method 
  of 
  

   obtaining 
  the 
  true 
  rainfall 
  from 
  gage 
  readings, 
  Professor 
  Abbe 
  

   suggests 
  the 
  following 
  as 
  offering 
  a 
  fair 
  approximation 
  : 
  

  

  If 
  the 
  present 
  gage 
  has 
  been 
  standing 
  in 
  an 
  open 
  field 
  at 
  a 
  few 
  

   feet 
  elevation, 
  place 
  two 
  or 
  more 
  similar 
  gages 
  near 
  it, 
  and 
  simi- 
  

   larly 
  located 
  as 
  far 
  as 
  obstacles 
  are 
  concerned, 
  except 
  only 
  that 
  

   one 
  of 
  these 
  is 
  to 
  be 
  decidedly 
  lower 
  than 
  the 
  old 
  one 
  and 
  the 
  

   other 
  decidedly 
  higher. 
  From 
  a 
  comparison 
  of 
  the 
  simultaneous 
  

   records 
  of 
  any 
  two 
  gages 
  and 
  their 
  altitudes, 
  we 
  should 
  for 
  each 
  

   separate 
  rainfall, 
  rather 
  than 
  for 
  the 
  monthly 
  and 
  annual 
  sums, 
  

   deduce 
  the 
  normal 
  rainfall 
  by 
  the 
  solution 
  of 
  two 
  or 
  more 
  equa- 
  

   tions 
  of 
  the 
  form 
  : 
  

  

  Observed 
  catch 
  of 
  gage-— 
  (1 
  — 
  x 
  altitude) 
  x( 
  desired 
  catch 
  of 
  normal 
  

   pit 
  gage). 
  (1) 
  

  

  