other line of argument, which I shall now
notice briefly in conclusion. This second argument is, that the general
diffusion of intelligence in a community tends to quicken invention, and
leads to the discovery of those scientific principles and of those
ingenious labor-saving machines, by which the productive power of the
community is so greatly multiplied. The cotton-gin, the steam-engine,
the sewing-machine, and the reaping-machine would never have been
invented in a nation of boors. It is not asserted that every boy who
goes to school will become an inventor. But it is as certain as the laws
of mind and matter can make it, that inventions abound in a nation in
proportion to its progress in science and the general spread of
intelligence among the masses. Multiply common schools and you multiply
inventions. How much these latter increase man's producing power, and
so add to the aggregate of human wealth, it is needless to say. The
invention of Watt alone has quadrupled the productive power of the whole
human race. The aggregate steam-power of one single country, Great
Britain, equals the muscular capacity for labor of four hundred millions
of men--more than twice the number of adult males capable of labor on
our planet. Its aggregate power throughout the earth is equal to the
male capacity for manual work of four or five worlds like ours. The
commerce, the navigation, the maritime warfare, the agriculture, the
mechanic arts of the human race, have been revolutionized by this single
invention not yet a century old.

The application of scientific truths to the common industries of life is
becoming every day more and more a necessity. The village carpenter, no
less than the builder of the Niagara Suspension Bridge, makes hourly
reference to scientific laws. The carpenter who misapplies his formulae
for the strength of materials, builds a house which falls down. The
properties of the various mechanical powers are involved in every
machine. Every machine, indeed, it has been well said, is a solidified
mechanical theorem. The surveyor in determining the limits of one's
farm, the architect in planning a house, the builder in planning his
estimates, and the several master workmen who do the carpentry, masonry,
and finishing, are all dependent upon geometric truths. Bleaching,
dyeing, calico-printing, gas-making, soap-making, sugar-refining, the
reduction of metals from their ores, with innumerable other productive
industries,