﻿HYDROLOGY 
  OF 
  NEW 
  YORK 
  315 
  

  

  exact 
  to 
  justify 
  the 
  labor 
  of 
  preparing 
  a 
  tabulation 
  of 
  this 
  

   character. 
  1 
  

  

  Referring 
  to 
  the 
  tabulation 
  on 
  page 
  oil, 
  it 
  is 
  learned 
  that 
  the 
  

   rainfall 
  in 
  that 
  portion 
  of 
  the 
  basin 
  of 
  the 
  Great 
  Lakes 
  tributary 
  

   to 
  Niagara 
  river 
  was, 
  for 
  1868, 
  523,420 
  cubic 
  feet 
  per 
  second, 
  and 
  

   the 
  evaporation 
  from 
  the 
  water 
  surface 
  of 
  the 
  lakes 
  tributary 
  to 
  

   Niagara 
  river 
  was 
  101,890 
  cubic 
  feet 
  per 
  second. 
  Hence 
  the 
  

   evaporation 
  from 
  the 
  lake 
  surfaces 
  was 
  nearly 
  20 
  per 
  cent 
  of 
  the 
  

   rainfall 
  on 
  the 
  whole 
  basin. 
  Assuming 
  for 
  the 
  moment 
  the 
  truth 
  

   of 
  these 
  figures, 
  we 
  have 
  80 
  per 
  cent 
  of 
  the 
  total 
  rainfall 
  from 
  

   which 
  the 
  land 
  evaporation 
  must 
  be 
  deducted 
  before 
  anything 
  can 
  

   run 
  off. 
  Again 
  assuming 
  the 
  land 
  evaporation 
  at 
  1.70 
  feet, 
  there 
  

   results 
  a 
  loss 
  from 
  this 
  source 
  alone 
  of 
  298,000 
  cubic 
  feet 
  per 
  

   second; 
  adding 
  to 
  this 
  the 
  evaporation 
  loss 
  from 
  the 
  water 
  sur- 
  

   faces 
  gives 
  a 
  total 
  evaporation 
  loss 
  of 
  399,890 
  cubic 
  feet 
  per 
  

   second. 
  The 
  runoff 
  is 
  the 
  difference 
  between 
  rainfall 
  and 
  total 
  

   evaporation 
  losses. 
  If, 
  therefore, 
  the 
  land 
  evaporation 
  was 
  1.7 
  

   feet 
  for 
  the 
  year 
  1868. 
  the 
  runoff 
  would 
  have 
  been 
  in 
  reality 
  only 
  

  

  1 
  There 
  have 
  been 
  a 
  number 
  of 
  independent 
  measurements 
  of 
  volume 
  of 
  the 
  

   Niagara, 
  and 
  though 
  the 
  results 
  differ 
  widely, 
  they 
  probably 
  do 
  not 
  differ 
  

   more 
  than 
  the 
  actual 
  volume 
  of 
  the 
  river 
  at 
  various 
  stages 
  of 
  Lake 
  Erie. 
  

  

  Lyell 
  (1841 
  ?) 
  quotes 
  Ruggles 
  as 
  authority 
  for 
  a 
  volume 
  of 
  250,000 
  cubic 
  

   feet 
  per 
  second. 
  

  

  E. 
  R. 
  Blackwell, 
  computed 
  by 
  Allen 
  (Am. 
  Jour. 
  Sci., 
  1841), 
  obtains 
  374,000 
  

   cubic 
  feet 
  per 
  second. 
  His 
  work 
  was 
  afterwards 
  recomputed 
  by 
  D. 
  F. 
  

   Henry, 
  who 
  obtained 
  244,797 
  cubic 
  feet 
  per 
  second. 
  

  

  In 
  the 
  Annual 
  Report 
  of 
  the 
  Chief 
  of 
  Engineers, 
  United 
  States 
  Army, 
  

   for 
  1867-68, 
  D. 
  F. 
  Henry 
  gives 
  as 
  a 
  result 
  of 
  observations 
  in 
  August 
  and 
  

   September, 
  1867. 
  242,494 
  cubic 
  feet 
  per 
  second. 
  A 
  year 
  later 
  he 
  recom- 
  

   puted 
  from 
  the 
  same 
  data, 
  and 
  obtained 
  240,192 
  cubic 
  feet 
  per 
  second. 
  He 
  

   also 
  made 
  a 
  new 
  measurement 
  by 
  a 
  different 
  method 
  (see 
  report 
  for 
  1868- 
  

   V>9) 
  from 
  which 
  he 
  obtained 
  two 
  results, 
  304,307 
  and 
  258,586 
  cubic 
  feet 
  per 
  

   second. 
  

  

  W. 
  F. 
  Reynolds 
  (Annual 
  Report 
  of 
  the 
  Chief 
  of 
  Engineers, 
  United 
  States 
  

   Army, 
  1870?), 
  gives 
  the 
  result 
  of 
  observations 
  from 
  June 
  to 
  September, 
  

   1869, 
  212,860 
  cubic 
  feet 
  per 
  second. 
  

  

  In 
  the 
  Annual 
  Report 
  of 
  the 
  Chief 
  of 
  Engineers, 
  United 
  States 
  Army, 
  for 
  

   1871, 
  there 
  is 
  a 
  mention 
  of 
  a 
  result, 
  without 
  date 
  of 
  measurement, 
  245,296 
  

   cubic 
  feet 
  per 
  second. 
  

  

  In 
  the 
  Annual 
  Report 
  of 
  the 
  Chief 
  of 
  Engineers, 
  United 
  States 
  Army, 
  for 
  

   1891-92, 
  Quintus, 
  as 
  a 
  result 
  of 
  gaging, 
  gives 
  the 
  volume, 
  reduced 
  to 
  mean 
  

   stage, 
  as 
  232,800 
  cubic 
  feet 
  per 
  second. 
  

  

  Sir 
  Casimir 
  S. 
  Gzowski, 
  from 
  continuous 
  observations 
  at 
  the 
  Inter- 
  

   national 
  bridge, 
  1870-1873, 
  gives 
  an 
  average 
  discharge 
  for 
  that 
  period 
  of 
  

   246,000 
  cubic 
  feet 
  per 
  second. 
  

  

  