RENT

205

conveyed  along  costly  aqueducts.  To  be
strictly  logical,  if  we  take  the  narrower  view
of  rent,  we  ought  to  say  that  the  marginal
land  earns  its  marginal  worth  (a  scarcity
price)  and  not  rent,  but  that  super-marginal
land  earns  its  marginal  worth  plus  an
extra  sum  (differential  rent)  which  measures
the  differential  advantages  enjoyed  by  it,  that
is  to  say,  a  sum  which  would  render  the  substitution ­
  of  that  land  for  marginal  land  a  matter
of  indifference.
It  goes  without  saying  that  the  payment
for  land  of  a  sum  representing  its  marginal
worth  is  a  phenomenon  foreign  to  our  experience. ­
  Even  under  conditions  of  such  a
kind  that  a  community  is  dependent  for  its
food  upon  the  produce  of  its  own  country,  it
will  generally  be  found  that  there  is  some  land
of  some  quality,  though  it  may  be  of  a  very
low  quality  and  very  inconveniently  located,
which  has  not  yet  been  brought  under  the
plough  or  used  for  grazing.  And  when  we
come  to  modern  conditions  wherein  all
parts  of  the  world  are  linked  together  by
international  trade,  we  find  unlimited  tracts
of  unoccupied  land  available  for  the  production ­
  of  the  food  supply  of  the  future
population.  Hence  it  is  readily  comprehensible ­
  why  it  is  that  in  economic  writings