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the  distance  apart  depending  upon  the  nature  of  the  land  and  the 
slope  of  the  surface,  as  in  case  of  sidehill  ditches.  Theoretically, 
it  is  intended  to  have  the  surface  between  these  two  furrows  level 
so  that  there  will  he  no  chance  for  the  water  to  run  off  over  the 
surface.  On  a small  scale  this  levelling  can  be  done  with  a horse 
shovel,  and  tlie  land  thus  put  once  into  a condition  to  prevent 
washing.  In  this  case  the  banks  of  the  terrace  are  sodded  or  seeded 
with  grass  to  prevent  them  from  washing.  In  the  held  practice, 
however,  the  soil  is  moved  gradually  with  a plough,  the  furrow  be- 
ing thrown  always  downhill  and  the  soil  gradually  worked  down  to 
a level  plain.  There  are  sever. d forms  of  reversible  ploughs  which 
are  admirably  adapted  to  this  purpose,  being  turned  readily  from  a 
right  to  a left  handed  plough,  so  that  in  going  back  and  forth  the 
furrow  is  always  thrown  downhill.  If  requires,  of  course,  a num- 
ber of  years  of  such  cultivation  to  get  the  surface  into  even  approxi- 
mately a level  condition,  but  with  patience  and  thorough  cultivation 
the  soil  very  quickly  assumes  a comparatively  level  aspect  and 
erosion  is  reduced  to  a minimum.  This  is  a more  expensive  method, 
but  if  intelligently  done  it  is  much  more  efficient  and  much  more 
durable  than  depending  upon  sidehill  ditclies  to  prevent  erosion. 
As  was  said  in  the  case  of  the  sidehill  ditches,  unless  this  work  is 
well  done  it  had  much  better  be  left  undone,  as  it  may  seriously 
injure  the  held. 
Where  erosion  has  proceeded  so  far  as  to  render  the  land  at  pre- 
sent unht  for  cultivation,  or  where  the  land  is  not  needed  for  cul- 
tivation and  it  is  desired  to  prevent  erosion,  the  land  should  be 
given  up  to  trees,  herbs,  or  grasses  of  some  kind  according  to  one 
or  other  of  the  following  methods. 
Recovering  Gullied  Hillsides  by  Reforestation. 
Forest  ground  is  not  subject  to  this  erosive  action  of  the  rainfall 
because  in  a forest  a large  part  of  the  rainfall  never  reaches  the 
soil,  as  20  or  30  per  cent,  is  intercepted  by  the  foliage  and  eva- 
porated before  it  reaches  the  ground.  The  rainfall  which  reaches 
the  surface  is  rapidly  absorbed,  as  the  soil  is  kept  granular  and 
loose  and  much  more  of  the  water  is  carried  off  by  underdrainage 
rather  than  by  surface  drainage. 
The  forest  covering  protects  the  soil  in  the 
FOLLOWING  WAVS. 
1.  By  preventing  rain  from  tailing  directly  upon  the  soil,  the 
foliage  of  the  tree  crowns  intercepting  and  breaking  its  force,  the 
water  reaching  the  soil  more  gently  from  the  leaves  and  along  the 
branches  and  trunks  of  the  trees. 
2.  By  interposing  a loose  cover  or  mulch  of  litter  formed  by 
the  fallen  leaves  and  branches,  which  breaks  the  direct  force  of  the 
raindrops  and  keeps  the  soil  from  being  compacted  or  puddled  by 
their  blow. 
3.  The  deeply  penetrating  roots,  and  holes  left  from  decayed 
stumps  and  roots  of  trees,  assist  in  this  underground  drainage. 
