produced a great revolution in national policy.

In former ages wars were made for the procuring of slaves. A conqueror
transported entire populations, and extorted from them forced labor, for
it was only by human labor that human labor could be relieved. But when
it was discovered that physical agents and mechanical combinations could
be employed to incomparably greater advantage, public policy underwent a
change; when it was recognized that the application of a new principle,
or the invention of a new machine, was better than the acquisition of an
additional slave, peace became preferable to war. And not only so, but
nations possessing great slave or serf populations, as was the care in
America and Russia, found that considerations of humanity were supported
by considerations of interest, and set their bondmen free.

SCIENTIFIC INVENTIONS. Thus we live in a period of which a
characteristic is the supplanting of human and animal labor by machines.
Its mechanical inventions have wrought a social revolution. We appeal
to the natural, not to the supernatural, for the accomplishment of our
ends. It is with the "modern civilization" thus arising that Catholicism
refuses to be reconciled. The papacy loudly proclaims its inflexible
repudiation of this state of affairs, and insists on a restoration of
the medieval condition of things.

That a piece of amber, when rubbed, will attract and then repel light
bodies, was a fact known six hundred years before Christ. It remained an
isolated, uncultivated fact, a mere trifle, until sixteen hundred years
after Christ. Then dealt with by the scientific methods of mathematical
discussion and experiment, and practical application made of the result,
it has permitted men to communicate instantaneously with each other
across continents and under oceans. It has centralized the world. By
enabling the sovereign authority to transmit its mandates without
regard to distance or to time, it has revolutionized statesmanship and
condensed political power.

In the Museum of Alexandria there was a machine invented by Hero, the
mathematician, a little more than one hundred years before Christ. It
revolved by the agency of steam, and was of the form that we should
now call a reaction-engine. This, the germ of one of the most important
inventions ever made, was remembered as a mere curiosity for seventeen
hundred years.

Chance had nothing to do with the invention of the modern steam-engine.
It was