﻿164 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  We 
  have 
  seen 
  in 
  the 
  preceding 
  that 
  it 
  is 
  somewhat 
  uncertain 
  

   whether 
  difference 
  in 
  soil 
  due 
  to 
  difference 
  in 
  character 
  of 
  rocks 
  

   has 
  much 
  influence 
  on 
  the 
  runoff, 
  although 
  casually 
  it 
  appears 
  that 
  

   sandy 
  soils, 
  from 
  their 
  porousness, 
  do 
  considerably 
  affect 
  tbe 
  

   result. 
  Recent 
  European 
  studies 
  of 
  this 
  subject 
  have 
  shown 
  

   (1) 
  that 
  in 
  many 
  river 
  basins 
  the 
  annual 
  runoff 
  stands 
  in 
  a 
  nearly 
  

   constant 
  relation 
  to 
  the 
  rainfall, 
  and 
  (2) 
  that 
  this 
  constancy 
  is 
  

   more 
  marked 
  when 
  the 
  excess 
  rain 
  fall 
  above 
  a 
  certain 
  minimum 
  

   annual 
  depth 
  is 
  considered. 
  This 
  latter 
  statement 
  is 
  equivalent 
  to 
  

   saying 
  that 
  if 
  the 
  yearly 
  rainfall 
  is 
  less 
  than 
  such 
  minimum 
  depth 
  

   little 
  or 
  no 
  runoff 
  will 
  take 
  place. 
  1 
  

  

  The 
  general 
  truth 
  of 
  this 
  proposition 
  is 
  shown 
  by 
  many 
  western 
  

   streams 
  where 
  the 
  runoff 
  is 
  little 
  or 
  nothing. 
  In 
  New 
  Jersey 
  12 
  

   inches 
  of 
  rain 
  during 
  the 
  summer 
  season 
  produce 
  a 
  runoff 
  of 
  1.5 
  

   inches, 
  though 
  others 
  have 
  stated 
  a 
  somewhat 
  different 
  relation. 
  

   In 
  the 
  State 
  of 
  New 
  York 
  from 
  1.7 
  to 
  2 
  inches 
  may 
  be 
  considered 
  

   the 
  general 
  range. 
  As 
  to 
  the 
  amount 
  of 
  rain 
  required 
  to 
  produce 
  

   any 
  runoff 
  at 
  all, 
  from 
  12.5 
  to 
  16.5 
  inches 
  have 
  been 
  given. 
  For 
  

   this 
  minimum 
  many 
  western 
  streams 
  do 
  not 
  run 
  more 
  than 
  0.25 
  

   to 
  0.5 
  inch, 
  and 
  some 
  even 
  are 
  perfectly 
  dry. 
  These 
  statements 
  

   indicate 
  that 
  the 
  character 
  of 
  the 
  soil, 
  nature 
  of 
  vegetation, 
  the 
  

   elevation, 
  etc. 
  are 
  of 
  comparatively 
  small 
  importance 
  as 
  regards 
  

   relation 
  between 
  the 
  yearly 
  volumes 
  of 
  rainfall 
  and 
  runoff. 
  If, 
  

   however, 
  we 
  consider 
  the 
  rainfall 
  and 
  runoff 
  of 
  the 
  several 
  periods, 
  

   as 
  shown 
  by 
  the 
  accompanying 
  tables, 
  it 
  is 
  not 
  entirely 
  certain 
  

   that 
  these 
  propositions 
  are 
  other 
  than 
  approximately 
  true. 
  The 
  

   weight 
  of 
  evidence 
  indeed 
  is, 
  on 
  the 
  whole, 
  negative. 
  Mr 
  Ver- 
  

   meule 
  is 
  disposed 
  to 
  attribute 
  nearly 
  all 
  of 
  the 
  differences 
  between 
  

   streams 
  to 
  difference 
  in 
  geology, 
  and 
  accordingly 
  gives 
  a 
  geologic 
  

   classification 
  for 
  the 
  New 
  Jersey 
  streams. 
  Mr 
  Vermeule 
  says: 
  

  

  As 
  a 
  rule, 
  the 
  watersheds 
  which 
  lie 
  upon 
  the 
  same 
  geological 
  

   formation 
  will 
  be 
  found 
  to 
  have 
  a 
  strong 
  resemblance, 
  both 
  in 
  the 
  

   character 
  of 
  flow 
  and 
  in 
  the 
  chemical 
  composition 
  of 
  the 
  waters. 
  

  

  Yet, 
  as 
  will 
  be 
  shown 
  later, 
  the 
  Genesee 
  and 
  Oswego 
  rivers, 
  two 
  

   streams 
  with 
  approximately 
  the 
  same 
  runoff, 
  lie 
  mostly 
  in 
  differ- 
  

   l 
  Barge 
  Canal 
  Report, 
  p. 
  798. 
  

  

  