rnishings; but if he has a
tolerable supply of such things, he will hardly choose to add to it by
staying in the shop when his strength has been exhausted and he is
eager to reach his home.

_Specific Cost at its Maximum a Measure of Specific Utility._--Two
very important principles are at work whenever a man is performing
labor in order to create wealth. The more consumers' wealth he gets,
the less important to him are the successive units of it, and the more
do these successive units cost him. The tenth hour of labor adds to
his supply of food, but this addition is not as important as the
supplies that were already on hand. If we divide the supply into
tenths and let the man produce a tenth in each successive hour, the
first tenth, which rescues him from starvation, is the most important,
while the last tenth, which comes nearest to glutting his appetite, is
least important. This last increment, however, is produced by the
greatest sacrifice, for it is gained by making the working day ten
hours long instead of nine.

[Illustration]

Let the hours of the working day be counted along the line _AD_, and
let us suppose that a man gets unit after unit of consumers' wealth,
as he works hour after hour, and the units grow less and less
important. The first and most important we may measure by the vertical
line _AB_. The second is worth less, the third still less, and the
last one is worth only the amount _CD_. This means that the successive
units of what we may call general commodity for personal use have
declined in utility along the curve _BC_. On the other hand, as the
man's labor has been prolonged, it has grown more and more wearying
and irksome. The sacrifice that it involved at first was almost
nothing, but the sacrifice of the succeeding hours has increased
until, in the last hour, it amounts to the quantity expressed by
_CD_.[2] As the man has continued to work, the onerousness of working
has increased along the ascending line _AC_ until the point has been
reached where it is so great that it is barely compensated by the
fruits of the labor. The man will then work no longer. If he were to
do so, his sacrifice would become still larger and his reward still
less. Up to this point it is profitable to work, for every hour of
labor has brought him something so useful that it has more than paid
for whatever sacrifice he has made in order to get it. Beyond this
point this is not the case. The line _CD_ represents the c