al methods are improving, and the organization of productive
establishments is perfecting itself; while over against these changes
in industry is an evolution in the wants of the individual consumer,
whom industry has to serve. The nature, the causes, and the effects of
these changes are among the subjects treated in this volume.

The Political Economy of the century following the publication of the
"Wealth of Nations" dealt more with static problems than with dynamic
ones. It sought to obtain laws which fixed the "natural" prices of
goods and those which, in a like way, governed the natural wages of
labor and the interest on capital. This term _natural_ as thus used,
was equivalent to static. If the laws of value, wages, and interest
had at this time been correctly stated, they would have furnished
standards to which, in the absence of all change and disturbance,
actual values, wages, and interest would ultimately have conformed.
The economic theory of this time succeeded in formulating, correctly
or otherwise, principles of economic statics and a fragment or two of
a science of economic dynamics, although the distinction between the
two divisions of the science was not clearly before the writers' eyes.
The law of population contained in the work of Malthus is the only
systematic statement then made of a general law of economic change.
Though histories of wages, prices, etc., furnished some material for a
science of Economic Dynamics, none of them attained the dignity of a
presentation of law or merited a place in Economic Theory. Students of
Political Economy were at that date scarcely awakened to the
perception of laws of dynamics, and still less were they conscious of
the need of a systematic statement of them. A modest beginning in the
way of formulating such laws the present work endeavors to make.

The first fact which becomes apparent when economic progress is
studied, is that static laws have a general application and are as
efficient in a society which is undergoing rapid transformation as in
one that is altogether changeless. Water in a tranquil pool is
affected by static forces. Let a quantity of other water rush in and
there are superinduced on these forces others which are highly
dynamic. The original forces are as strongly operative as ever, and if
the inflow were to stop, would again reduce the surface to a level.
The laws of hydrostatics affect the waters in the rapids of Niagara as
truly as they do th