﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  139 
  

  

  accepting 
  it 
  for 
  one 
  month 
  as 
  true, 
  because 
  rainfall 
  or 
  snowfall 
  

   at 
  the 
  end 
  of 
  the 
  month 
  can 
  be 
  easily 
  carried 
  over 
  to 
  the 
  next. 
  

   This 
  is 
  also 
  true 
  sometimes 
  for 
  two 
  months, 
  but 
  for 
  the 
  present 
  

   it 
  seems 
  quite 
  doubtful 
  that 
  other 
  than 
  in 
  exceedingly 
  rare 
  cases 
  

   would 
  negative 
  evaporation 
  occur 
  for 
  three 
  consecutive 
  months. 
  

   Its 
  occurrence 
  for 
  six 
  consecutive 
  months, 
  or 
  for 
  the 
  entire 
  storage 
  

   period, 
  is 
  believed 
  to 
  be 
  impossible. 
  It 
  may, 
  however, 
  be 
  again 
  

   pointed 
  out 
  that 
  its 
  occurrence 
  renders 
  an 
  attempt 
  at 
  monthly 
  

   diagrams 
  showing 
  the 
  relation 
  between 
  rainfall 
  and 
  runoff 
  absurd. 
  

  

  Assuming 
  that 
  the 
  foregoing 
  propositions 
  are 
  reasonably 
  true, 
  

   it 
  follows 
  that 
  the 
  frequency 
  of 
  the 
  occurrence 
  of 
  negative 
  

   evaporation 
  in 
  gaging 
  records 
  may 
  be 
  in 
  some 
  degree 
  a 
  criterion 
  

   as 
  to 
  their 
  accuracy. 
  The 
  writer, 
  however, 
  does 
  not 
  wish 
  to 
  urge 
  

   this 
  very 
  strongly, 
  but 
  merely 
  to 
  point 
  it 
  out 
  as 
  a 
  possibility. 
  

   The 
  writer 
  has 
  no 
  desire 
  to 
  be 
  insistent 
  on 
  this 
  point. 
  There 
  is 
  

   very 
  little 
  on 
  the 
  subject 
  of 
  negative 
  evaporation 
  in 
  engineering 
  

   literature, 
  and 
  the 
  writer 
  will 
  be 
  glad 
  to 
  have 
  the 
  observations 
  

   and 
  conclusions 
  of 
  others. 
  

  

  In 
  a 
  report 
  on 
  the 
  flow 
  of 
  the 
  river 
  Thames, 
  by 
  A. 
  R. 
  Binnie, 
  

   Chief 
  Engineer 
  of 
  the 
  London 
  County 
  Council, 
  1 
  the 
  matter 
  of 
  nega- 
  

   tive 
  evaporation 
  is 
  elaborately 
  discussed, 
  and 
  in 
  order 
  to 
  obtain 
  

   all 
  the 
  information 
  possible 
  about 
  it 
  Mr 
  Binnie 
  applied 
  to 
  

   George 
  J. 
  Symons, 
  F. 
  R. 
  S., 
  to 
  assist 
  him 
  in 
  arriving 
  at 
  some 
  

   approximate 
  idea 
  on 
  the 
  subject. 
  Mr 
  Symons 
  submitted 
  an 
  exceed- 
  

   ingly 
  lucid 
  and 
  conclusive 
  report. 
  Eleven 
  distinct 
  cases 
  of 
  nega- 
  

   tive 
  evaporation 
  were 
  submitted 
  to 
  him 
  for 
  study 
  and 
  comment. 
  

   In 
  regard 
  to 
  these 
  he 
  arrived 
  at 
  the 
  following 
  conclusions 
  : 
  

  

  1) 
  Under 
  normal 
  conditions 
  a 
  fall 
  of 
  rain 
  will 
  increase 
  the 
  flow 
  

   at 
  Teddington 
  weir 
  on 
  the 
  second 
  day 
  after 
  it 
  falls. 
  

  

  2) 
  Under 
  normal 
  conditions 
  the 
  water 
  running 
  off 
  from 
  any 
  

   given 
  fall 
  of 
  rain 
  will 
  all 
  reach 
  Teddington 
  weir 
  before 
  the 
  tenth 
  

   subsequent 
  day. 
  

  

  3) 
  In 
  the 
  winter 
  an 
  interval 
  of 
  two 
  months, 
  or 
  in 
  extreme 
  

   cases 
  even 
  more, 
  may 
  elapse 
  between 
  the 
  precipitation 
  of 
  moisture 
  

   from 
  the 
  clouds 
  and 
  its 
  flow 
  over 
  Teddington 
  weir. 
  

  

  Report 
  on 
  the 
  Flow 
  of 
  the 
  River 
  Thames, 
  by 
  A. 
  R. 
  Binnie. 
  Publication 
  

   of 
  the 
  London 
  County 
  Council, 
  dated 
  November 
  1, 
  1892. 
  

  

  . 
  

  

  