253 
crops,  or  rye,  oats,  or  field  peas  should  be  sown  to  help  hold  the 
surface.  Little  by  little,  but  inoia?  rapidly  than  would  be  expected 
from  the  forbidding  aspect  of  the  field,  the  land  can  be  re;  lairned 
again  and  made  productive  througli  the  accumulation  of  humus  and 
organic  matter.  .A  soil  containing  a fair  quantity  of  humus  will 
wash  less  readily  than  one  nearly  destitute  of  this  matter. 
A soil  containing  a fair  supply  cf  lime  is  much  less  liable  to 
wash  than  one  similarly  situated  and  exposed  which  is  deficient  in 
lime.  The  reason  of  this  is  that  clays  whi^h  are  deficient  in  lime, 
when  once  brought  into  suspension  by  moving  waters,  will  remain 
in  suspension  and  keep  the  water  turbid  for  a long  time.  Clays 
which  are  heavily  impregnated  with  lime  salts,  on  the  otlmr  hand, 
are  in  a flocculated  state,  the  fine  grains  of  clay  being  held  together 
and  in  contact  with  the  larger  grains  of  sand.  This  flocculated 
mass  quickly  settles  and  is  originally  not  so  easily  disturbed  and 
carried  off  by  moving  water.  .\  field  treated  with  an  abundance 
of  lime  is  thus  less  easily  washed  by  heavy  rains.  1 he  results  of 
investigations  by  Schulze,  Schloesing,  and  Hilgard  have  shown  in 
a most  emphatic  way  the  beneficial  changes  which  take  place, 
especially  in  stiff  clav  soils,  by  the  application  of  lime. 
The  change  in  the  physical  condition  of  the  soil  which  is  pro- 
duced by  the  lime,  and  which  is  likewise  produced  by  a number  of 
other  chemicals  ordinarily  used  in  commercial  fertilizers,  is  another 
important  factor  worthv  of  consideration.  .A  stiff  clay  soil  is 
practically  impervious  to  the  penetration  of  surface  water  when  it 
is  delivered  in  such  torrents  as  we  are  liable  to  have  in  our  summer 
storms.  A well-limed  soil,  on  the  contrary,  although  it  may  con- 
tain as  much  clay  but  in  which  the  particles  are  flocculated  or 
drawn  together,  is  much  more  pervious  to  water,  and  the  amount 
of  water' which  the  soil  will  carry  down  through  underdrainage  is 
increased,  and  the  excess  which  has  to  flow  off  over  the  surface  is 
diminished.  The  surface  washing  of  cultivated  fields,  especially 
those  which  are  naturally  deficient  in  lime,  can  be  greatly  dimin- 
ished, therefore,  by  the  free  application  of  this  substance  to  them. 
.A  number  of  the  ordinary  fertilizing  materials  have  an  important 
effect  upon  the  texture  of  soils  and  upon  the  permeability  of  soils 
to  water,  but  few  systematic  investigations  have  been  carried  on 
in  this  line  and  not  much,  except  of  local  importance,  has  been 
definitely  settled  by  experiments  or  by  the  experiences  of  farmers. 
Washing  of  lands  may  br  prlvented  by  methods  of 
CULTIVATION  AND  UNDER  DRAIN  AGE. 
The  depth  and  character  of  the  tillage  are  very  impoitant  factors, 
in  the  washing  of  lands.  A field  in  a condition  ol  fine  tilth  and 
ploughed  to  a depth  of  ten  inche.s  will  hold  two  inches  of  rain  fall 
and  absorb  it  very  readily,  and  a soil  in  such  a condition  will  suflei' 
no  surface  washing  from  any  ordinary  rainfall.  Where  it  is  possi- 
ble, therefore,  land  which  is  liable  to  wash  should  have  the  soil 
gradually  deepf*m*d  and  bi‘  k*r*j-)t  in  a lim*  stat«'  ol  tilth  so  as  to  in- 
