The most potent influence of all, however, has been the matter of
internal economic development, stimulated by free trade among the
states. This development has gone on apace with little regard for state
lines. The invention of railways drew the different sections of the
country together in a common growth, and tended to make the barriers
interposed by state lines and state laws seem artificial and cumbersome.
In fact, they sometimes came to be regarded as intolerable and
destructive of progress. The spectacle of men clamoring for federal
control of their industries to escape the burdens of a diversified state
interference has been a frequent phenomenon of recent years.[1]

[Footnote 1: See e.g. the efforts of the life insurance interests: _N.Y.
Life Ins. Co. v. Deer Lodge County_, 231 U.S., 495.]

The foregoing enumeration by no means covers all the forces which have
been at work. In recent years a strong tendency toward centralization
and combination has developed, a tendency pervading all the interests
and activities of men. Moreover, new views have arisen concerning the
functions and scope of government, views challenging the _laissez faire_
doctrines of earlier days and demanding a greater measure of
governmental interference with the affairs of the individual. These
tendencies, however, are not peculiar to America and lie outside the
scope of the present discussion.

In considering the methods by which the change of spirit toward the
Constitution has been put into effect, one is struck by the
comparatively small part played by the only method contemplated by the
framers, viz., constitutional amendment. This method is entirely
practicable and fairly expeditious provided a sufficient number favor