﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  47 
  

  

  of 
  the 
  United 
  States, 
  and 
  has 
  since 
  been 
  operated 
  as 
  a 
  bureau 
  of 
  

   that 
  department. 
  Complete 
  observations 
  are 
  taken 
  at 
  the 
  six 
  

   original 
  stations 
  established 
  by 
  the 
  United 
  States 
  Signal 
  Service, 
  

   including 
  barometer, 
  temperature, 
  dewpoint, 
  relative 
  humidity, 
  

   vapor 
  pressure, 
  precipitation, 
  wind, 
  cloudiness 
  and 
  electrical 
  

   phenomena. 
  Generally, 
  the 
  Kegents 
  and 
  the 
  Smithsonian 
  obser- 
  

   vations 
  only 
  included 
  temperature 
  and 
  precipitation, 
  although 
  

   there 
  were 
  a 
  few 
  exceptions 
  where 
  barometer 
  and 
  wind 
  were 
  

   taken. 
  The 
  Meteorological 
  Bureau 
  also 
  generally 
  confines 
  itself 
  

   to 
  temperature 
  and 
  precipitation, 
  except 
  that 
  at 
  the 
  central 
  office 
  

   at 
  Ithaca, 
  and 
  at 
  a 
  few 
  other 
  places, 
  barometer 
  and 
  cloudiness 
  

   are 
  taken. 
  The 
  same 
  statement 
  applies 
  to 
  the 
  work 
  of 
  the 
  

   Meteorological 
  Bureau 
  as 
  carried 
  on 
  under 
  the 
  direction 
  of 
  the 
  

   United 
  States 
  Department 
  of 
  Agriculture. 
  

  

  The 
  average 
  annual 
  temperature 
  is 
  generally 
  taken 
  as 
  decreas- 
  

   ing 
  with 
  altitude 
  at 
  the 
  ratio 
  of 
  1° 
  F. 
  to 
  every 
  300 
  feet 
  of 
  eleva- 
  

   tion, 
  the 
  rate 
  being 
  somewhat 
  below 
  this 
  average 
  in 
  winter 
  and 
  

   above 
  it 
  in 
  summer. 
  An 
  approximate 
  determination 
  for 
  the 
  State 
  

   indicates 
  that 
  the 
  rates 
  of 
  decrease 
  are 
  0.3° 
  F. 
  per 
  hundred 
  feet 
  

   elevation 
  for 
  the 
  winter, 
  and 
  0.4° 
  F. 
  per 
  hundred 
  feet 
  for 
  the 
  sum- 
  

   mer. 
  For 
  the 
  mountains 
  of 
  northern 
  New 
  York 
  a 
  much 
  smaller 
  

   variation 
  than 
  0.3° 
  F. 
  appears 
  to 
  hold 
  for 
  the 
  winter 
  months. 
  

  

  The 
  intimate 
  relation 
  which 
  exists 
  between 
  air 
  circulation 
  and 
  

   precipitation 
  in 
  New 
  York 
  is 
  one 
  of 
  the 
  most 
  interesting 
  facts 
  

   to 
  be 
  noted. 
  Owing 
  to 
  lack 
  of 
  moisture 
  in 
  the 
  continental 
  inte- 
  

   rior, 
  northwest 
  winds 
  in 
  the 
  spring, 
  summer 
  and 
  fall 
  are 
  essen- 
  

   tially 
  dry. 
  In 
  winter 
  their 
  dryness 
  proceeds 
  from 
  low 
  tempera- 
  

   ture 
  and 
  consequent 
  small 
  vapor-carrying 
  capacity. 
  The 
  winter 
  

   precipitation 
  is 
  due 
  almost 
  entirely 
  to 
  storm 
  areas 
  passing 
  either 
  

   actually 
  across 
  or 
  in 
  the 
  vicinity 
  of 
  this 
  State 
  and 
  deriving 
  their 
  

   supply 
  of 
  vapor 
  from 
  the 
  inflow 
  of 
  moist 
  air 
  w 
  r 
  hich 
  they 
  induce, 
  

   either 
  from 
  the 
  Atlantic 
  ocean 
  or 
  from 
  the 
  Gulf 
  region. 
  

  

  The 
  winter 
  months 
  — 
  December, 
  January, 
  and 
  February 
  — 
  have 
  

   somewhat 
  less 
  precipitation 
  than 
  either 
  of 
  the 
  other 
  seasons, 
  

   although 
  in 
  the 
  vicinity 
  of 
  the 
  Atlantic 
  coast, 
  on 
  the 
  southwestern 
  

   highlands 
  of 
  the 
  State, 
  and 
  in 
  the 
  region 
  of 
  the 
  Great 
  Lakes 
  the 
  

   winter 
  precipitation 
  is 
  relatively 
  large. 
  

  

  