RENT

201

tuted  for  any  of  quality  A,  it  must  be  at  the  best
that  of  quality  B  ;  and,  therefore,  the  inferior
will  have  to  be  substituted  for  the  superior.
Such  a  substitution  would  not  prove  profitable
until  the  rent  of  land  A  became  something
greater  than  what  would  be  lost  by  evacuating
some  of  A  and  occupying  in  its  place  some  of
B.  Hence  rent  of  land  A  can  be  no  more  than
10  bushels  an  acre.  And,  broadly  speaking,
it  can  be  no  less,  because  the  competition  of
farmers  for  the  better  land  would  force  up
its  annual  value  until  the  substitution  of
land  B  for  land  A  (in  view  of  the  rent  of  land
A)  was  a  matter  of  indifference.
Let  us  now  take  a  further  step  in  the
demonstration  and  suppose  that  the  demand
for  the  produce  of  the  soil  is  such  that  some  of
land  C  must  be  occupied.  Then  eventually  the
rent  of  B  would  be  15  bushels,  the  difference
between  the  yield  of  B,  50  bushels,  and  the
yield  of  C,  35  bushels  ;  and  the  rent  of
A  would  be  25  bushels  per  acre,  the  difference
between  its  yield,  60  bushels,  and  the  yield  of
C,  35  bushels.  Finally  when  D,  which  bears
15  bushels  an  acre,  is  tilled,  C  with  a  produce
of  35  bushels  an  acre  will  bear  a  rent  of  20
bushels,  that  is  35  minus  15.  B,  with  its  output
of  50  bushels  an  acre,  will  earn  a  rent  of  35
bushels,  that  is  50  minus  15  ;  and  the  rent  of