THE PROBLEM OF RENT 107

land. With building land, the plan on which capital is
expended in improvements is determined, as with agricultural
 land, by the prospective advantages to be secured
by such an expenditure of capital. But the nature of the
case makes a large part of the capital outlay on building
land such as gives its returns somewhat slowly, and changed
conditions, making a different kind of improvement more
advantageous, cannot, in general, meet with so prompt a
response as is possible as the result of like changes in
reference to agricultural land. Much of the capital represented
 by improvements of agricultural land gives a
return sufficient to replace it within a short period of years,
and thus opportunity is afforded to adapt the forms of
capital fairly quickly to the changing knowledge and needs
of agriculture, For the most part, similar changes in buildings
 in cities require a longer term of years before they can
be effected. The rent idea applied to an improved urban
site must generally be applied to the land and to a good
deal of capital effectively bound up with the land. In the
case of agricultural land, though the same is to some
extent true, the dissociation of land and capital can be more
easily conceived of, and occurs more rapidly, as a rule, in
practice.
For what is land-rent a payment? The Ricardian
phraseology is that it is the payment for the use of the
original and indestructible powers of the soil.” As Professor
Marshall has pointed out, the powers of the soil which are
original and indestructible are situation and area, implying
access to sunlight, rain, etc. Other properties of the soil
can be created and destroyed, but these are important as
determining whether it is worth while to attempt the modification
 of those other properties. As already indicated,
land as hired combines certain mechanical and chemical
conditions of the soil, which can be created or destroyed,
and the use of buildings, roads, etc., facilitating the working
of the land, with the use of the original and indestructible
powers referred to. Inasmuch as contracts for the hire of
tand aim at securing that its existing powers shall be
maintained, whether original or acquired, destructible or not,