Soils  with  a  very  high  percentage  of  total  sands
are  loose  and  open  and  possess  in  large  measure
the  characteristics  of  sand ;  those  with  less  sand
are  not  so  open  and  loose,  are  better  adapted  to
<;rop  production,  and  are  classed  as  loams.  Soils
with  a  high  percentage  of  silt,  such  as  the  loess
soils,  are  usually  easily  kept  in  the  best  of  physical
condition,  while  soils  with  a  high  percentage  of
clay  are  plastic,  retentive  of  moisture,  with  a
strong  tendency  to  form  clods  when  worked  in  a
wet  condition  and  to  shrink  and  crack  in  a  period
of  drought.
However,  the  data  afforded  by  a  mechanical
analysis  do  not  enable  the  farmer  to  fix  unerr-
ingly on  definite  methods  of  soil  management.  In
a  general  way  he  can  determine  whether  his  soil  is
heavy,  whether  it  is  likely  to  leach  or  whether  it
will  pulverize  satisfacljprily  under  proper  cultiva-
tion. The  investigations  conducted  by  the  Bureau
of  Soils  in  recent  years  show  that  the  adaptability
of  certain  soils  for  special  crops  can  be  determined
in  large  measure  by  a  mechanical  analysis.
Many  different  methods  of  mechanical  analysis
have  been  employed  by  European  and  American
investigators.  Two  of  the  American  methods  which
have  given  very  satisfactory  results  are  known
as  the  Osborne  method  (Rep.  Experiment  Station,
Conn.,  1886,  141 ;  1887,  144 ;  1888,  154 ;  Wiley
op.  cit.,  196),  and  the  Hilgard  method  (American
Journal  Science  and  Art,  1873, 288,  333;  California
Experiment  Station  Report,  1891-92,  248 ;  Wiley,
op.  cit.,  225 ;  pp.  366-369,  following).
