g it. If we credit to this
second unit of labor what it adds to the product that was created
before it came into the field, we shall find that it is a certain
positive amount, but obviously less than the total product which was
realized by the first unit _and all the capital_. It is even less than
a half of the product of the two units using all the capital. Perhaps
the first unit of labor, when it used all the capital, created ten
units of product; while the two units of labor, using this same
original amount of capital, produce sixteen units of product. The
clear addition to the original product which is caused by the added
labor of the second squad of workmen is only six units, while a half
of the total product after the addition to the labor has been made is
eight. This figure represents the amount we may attribute to one unit
of labor and a half of the total capital, while six represent what is
_causally_ due to one unit of bare labor only. With all the capital
and one unit of labor we get ten units of product, while the addition
of one unit of bare labor brings the total amount up to sixteen. Six
units find the cause of their existence in the presence of the second
unit of labor, and the second unit therefore shows, as compared with
the first, a diminished productivity.

_Product of the Third Unit of Labor._--We will now introduce a third
unit of labor, leaving the amount of capital still unchanged, but
again altering the forms of it so as to adapt them to the needs of a
still larger working force. We will make the buildings larger and
therefore, of necessity, cheaper in their forms and materials. We will
make the tools and machines more numerous and simple, and will do
everything that is necessary in order to make the fixed amount of
capital--the fund amounting to a given number of "dollars"--embody
itself in the number and the kinds of capital goods that are requisite
in order to supply three times the original number of workmen. The
third unit of labor now adds something to the product realized by the
first two, but the addition is smaller than it was in the case of the
second unit.

_Products of a Series of Units of Labor._--If we continue this process
till we have ten units of labor, employing the same amount of capital
as was formerly used by one, we shall find that each unit as it begins
to work adds less to the previous product than did the unit which
preceded it, and that the tenth unit adds the least o