﻿138 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  there 
  is 
  at 
  the 
  same 
  time 
  an 
  atmosphere 
  more 
  or 
  less 
  saturated, 
  

   with 
  an 
  absence 
  of 
  sunshine 
  ; 
  while 
  in 
  dry 
  seasons 
  the 
  scarcity 
  of 
  

   rain 
  results 
  in 
  great 
  dryness 
  of 
  the 
  soil, 
  with 
  scant, 
  slow 
  evapora- 
  

   tion. 
  1 
  

  

  'Negative 
  evaporation. 
  In 
  a 
  strictly 
  scientific 
  sense 
  this 
  term 
  is 
  

   taken 
  to 
  mean 
  that 
  when 
  the 
  temperature 
  of 
  the 
  evaporating 
  sur- 
  

   face 
  is 
  lower 
  than 
  the 
  dewpoint, 
  water 
  is 
  deposited 
  on 
  that 
  sur- 
  

   face. 
  As 
  regards 
  the 
  rainfall, 
  runoff, 
  and 
  evaporation 
  tables, 
  

   herewith 
  included, 
  negative 
  evaporation 
  means 
  that 
  the 
  runoff 
  

   for 
  certain 
  months 
  is 
  greater 
  than 
  the 
  rainfall. 
  Sometimes 
  this 
  

   may 
  legitimately 
  happen 
  when 
  a 
  heavy 
  rainfall 
  comes 
  at 
  the 
  end 
  

   of 
  the 
  month, 
  or 
  when, 
  with 
  much 
  snowfall, 
  the 
  temperature 
  of 
  

   the 
  month 
  is 
  mostly 
  below 
  freezing. 
  In 
  order 
  to 
  show 
  as 
  much 
  

   as 
  possible 
  in 
  regard 
  thereto, 
  the 
  writer 
  gives 
  the 
  detail 
  for 
  each 
  

   of 
  the 
  tables 
  of 
  Muskingum, 
  Genesee, 
  Croton 
  and 
  Hudson 
  rivers, 
  

   together 
  with 
  a 
  tentative 
  view 
  as 
  to 
  the 
  real 
  significance 
  of 
  the 
  

   so-called 
  negative 
  evaporation. 
  

  

  On 
  Muskingum 
  river, 
  during 
  the 
  8 
  years 
  gaged, 
  negative 
  evapo- 
  

   ration 
  is 
  shown 
  only 
  twice 
  for 
  one 
  month. 
  

  

  On 
  Genesee 
  river 
  the 
  detailed 
  tabulation 
  shows 
  negative 
  evapo- 
  

   ration 
  5 
  times 
  for 
  one 
  month 
  and 
  once 
  for 
  two 
  consecutive 
  months, 
  

   a 
  total 
  of 
  7 
  months 
  in 
  all. 
  

  

  On 
  Croton 
  river, 
  for 
  the 
  entire 
  period 
  of 
  32 
  years, 
  negative 
  

   evaporation 
  is 
  shown 
  29 
  times 
  for 
  one 
  month 
  and 
  6 
  times 
  for 
  two 
  

   consecutive 
  months, 
  a 
  total 
  of 
  41 
  months 
  in 
  all. 
  

  

  On 
  Hudson 
  river 
  negative 
  evaporation 
  is 
  shown 
  7 
  times 
  for 
  one 
  

   month 
  and 
  4 
  times 
  for 
  two 
  consecutive 
  months, 
  a 
  total 
  of 
  15 
  

   months. 
  

  

  The 
  writer 
  has 
  no 
  doubt 
  that, 
  except 
  in 
  very 
  cold 
  climates, 
  when 
  

   negative 
  evaporation 
  occurs 
  for 
  three 
  or 
  more 
  consecutive 
  months, 
  

   there 
  is 
  an 
  error 
  in 
  the 
  gagings. 
  He 
  also 
  doubts 
  their 
  accuracy 
  

   somewhat 
  when 
  negative 
  evaporation 
  appears 
  for 
  two 
  consecutive 
  

   months. 
  As 
  regards 
  the 
  storage 
  period, 
  there 
  is 
  no 
  difficulty 
  in 
  

  

  1 
  Since 
  the 
  presistency 
  of 
  evaporation 
  has 
  been 
  extensively 
  discussed 
  in 
  

   the 
  writer's 
  paper 
  on 
  Stream 
  Flow 
  in 
  Relation 
  to 
  Forests, 
  it 
  is 
  merely 
  

   touched 
  on 
  here. 
  

  

  