of capital and the use of machinery will usually enhance on balance
the demand for labor. Moreover, though this is not conclusive, there
is little room for doubt that an obstructive attitude towards the
extension of machinery in a particular country, or a particular
district, is misguided. For its effect must be to make production
more costly there than it is elsewhere, and to lead, slowly perhaps,
but very surely, to the transference of the industry to other regions.


§6. _Conclusions as to Joint Supply and Joint Demand_. Here, however,
we are beginning to digress. Let us sum up in a general form our
conclusions as to the way in which changes in the supply or demand of
a commodity react upon the demand or supply of the other things with
which it is jointly demanded or supplied. Everything turns, as we have
seen, on the possibility of variation in the proportions in which the
things are used or produced together; and this, it is also clear, is a
matter of degree. Our conclusions, therefore, had best take the
following form:--

LAW VII. When two or more things are jointly demanded, in proportions
which cannot easily be varied, the tendency will be for an increase
(or decrease) in the supply of one of them to increase (or
decrease) the demand for the others. These results will be more
certain, and more marked, the more difficult it is to vary the
proportions in which the things are used.

Similarly, when two or more things are jointly supplied, in
proportions which cannot easily be varied, the tendency will be for
an increase (or decrease) in the demand for one of them to increase
(or decrease) the supply of the others. These results again will be