he whole income of the society
consists in _A'''_'s, a certain number of the _A'''_'s that are
withdrawn for consumption go to capitalists as interest on the
permanent fund which is kept in existence in the form of _A_, _A'_,
_A''_, and _A'''_. A certain other part of the outflow of _A'''_'s
goes also to capitalists as interest on that other permanent fund
which is maintained in the form of tools, machines, and buildings,
such as must everywhere be used in the series. A third part of the
flow of _A'''_'s is wages of labor in this group; and a final portion
is what we have called the sinking fund, the amount that is given over
as an income to the producers in another group, not here represented,
who keep the stock of buildings, tools, etc., intact. These four
withdrawals of income constitute the process by which the stock of
passive goods is depleted, and the grand resultant of all industry is
to atone for that depletion.

_Labor and the Obtaining of its Product, in Static Industry,
Synchronous._--One function of the permanent series of _A_'s is to
enable labor everywhere to get its virtual product without waiting,
and that too in the form in which it needs it for use. The labor that
converts _A''_ into _A'''_ supplies the waste of tissue that takes
place at that end of the line by withdrawal of an _A'''_. The labor
that turns _A'_ into _A''_ replaces the waste that takes place at that
point when an earlier _A''_ becomes an _A'''_. The labor at _A'_
replaces the waste at that point, and that at _A_ replaces the waste
at still another point. They are all at work keeping the stock of
_A_'s unimpaired, and one of them does as much toward keeping up the
perpetual flow of _A'''_'s as any other.

If we pump water in at one end of a full reservoir, we instantly cause
it to overflow at the other end; and every worker in such a series as
we have described may be thought of as putting something into the
permanent reservoir of capital and so causing a corresponding
overflow. He gets his reward day by day as the work proceeds. Wherever
a laborer may be in such a series, his work creates a ripened product
as it goes on. He has not to wait for it. His work and its fruit are
synchronous.

_Differences between Land and Made Instruments Apparent in Dynamic
Conditions._--A point that has great theoretical interest is the
nature of the difference between land and other productive
instruments. In a static society the difference would be