﻿TIMBER; 
  FORESTRY 
  119 
  

  

  it 
  has 
  been 
  possible 
  for 
  people 
  interested 
  in 
  lumbering 
  to 
  

   assert 
  that 
  clearing 
  off 
  the 
  forests 
  may 
  do 
  no 
  harm 
  to 
  the 
  

   climate 
  of 
  the 
  country. 
  No 
  one 
  should 
  be 
  deceived 
  by 
  such 
  

   arguments, 
  since 
  it 
  is 
  a 
  well-ascertained 
  fact 
  that 
  the 
  ivater 
  

   supply 
  of 
  any 
  region 
  is 
  made 
  far 
  more 
  irregular 
  by 
  the 
  removal 
  

   of 
  its 
  forests. 
  The 
  annual 
  rainfall 
  may 
  not 
  be 
  greatly 
  changed, 
  

   but 
  the 
  rivers 
  of 
  a 
  deforested 
  country 
  are 
  likely 
  to 
  overflow 
  

   their 
  banks 
  after 
  all 
  heavy 
  rains, 
  and 
  then 
  almost 
  disappear 
  

   during 
  the 
  driest 
  part 
  of 
  the 
  summer. 
  A 
  notable 
  example 
  of 
  

   this 
  summer 
  shrinkage 
  in 
  rivers 
  is 
  that 
  of 
  the 
  Susquehanna 
  ; 
  

   in 
  1816 
  it 
  was 
  estimated 
  that 
  this 
  river 
  delivered 
  five 
  hundred 
  

   million 
  gallons 
  per 
  day 
  at 
  its 
  season 
  of 
  minimum 
  flow 
  ; 
  in 
  1874 
  

   this 
  had 
  shrunk 
  to 
  less 
  than 
  half 
  the 
  amount, 
  although 
  the 
  

   annual 
  rainfall 
  remained 
  about 
  the 
  same. 
  1 
  Every 
  one 
  who 
  has 
  

   lived 
  in 
  a 
  prairie 
  country 
  knows 
  that 
  the 
  run-off 
  from 
  grasslands 
  

   is 
  so 
  rapid 
  that 
  creeks 
  which, 
  during 
  a 
  dry 
  time, 
  consist 
  merely 
  

   of 
  a 
  series 
  of 
  pools 
  may 
  be 
  running 
  bank-full 
  after 
  an 
  hour 
  or 
  

   two 
  of 
  heavy 
  rain. 
  From 
  plowed 
  land 
  the 
  run-off 
  is 
  even 
  more 
  

   rapid 
  than 
  from 
  grass-covered 
  land. 
  It 
  is 
  difficult 
  to 
  ascertain 
  

   just 
  what 
  proportion 
  of 
  the 
  total 
  rainfall 
  is 
  temporarily 
  held 
  

   by 
  the 
  forest 
  floor. 
  On 
  careful 
  observation 
  of 
  a 
  wooded 
  basin 
  

   in 
  the 
  Cevennes 
  Mountains 
  in 
  southern 
  France, 
  in 
  which 
  some- 
  

   what 
  more 
  than 
  50 
  per 
  cent 
  was 
  forest, 
  it 
  was 
  found 
  that 
  after 
  

   two 
  days 
  of 
  heavy 
  rain 
  more 
  than 
  eight 
  ninths 
  of 
  the 
  total 
  

   rainfall 
  was 
  held 
  by 
  the 
  soil; 
  water 
  so 
  held 
  may 
  then 
  run 
  

   away 
  gradually. 
  2 
  

  

  The 
  action 
  of 
  forests 
  in 
  retaining 
  water 
  and 
  slowly 
  distrib- 
  

   uting 
  it 
  is 
  largely 
  due 
  to 
  the 
  following 
  causes 
  : 
  

  

  1. 
  Snow 
  melts 
  gradually 
  in 
  the 
  shade 
  of 
  forests, 
  and 
  so 
  

   the 
  water 
  derived 
  from 
  its 
  thawing 
  is 
  given 
  off 
  little 
  by 
  little. 
  

  

  2. 
  Evaporation 
  goes 
  on 
  slowly 
  in 
  the 
  shade. 
  

  

  3. 
  The 
  forest 
  floor 
  is 
  often 
  covered 
  to 
  a 
  considerable 
  depth 
  

   with 
  a 
  layer 
  of 
  highly 
  absorbent 
  material, 
  such 
  as 
  decaying 
  

  

  1 
  See 
  Fernow, 
  "Forest 
  Influences," 
  Bulletin 
  7, 
  Division 
  of 
  Forestry, 
  

   TJ. 
  S. 
  Dept. 
  Agr., 
  1893. 
  

  

  2 
  Ibid. 
  

  

  