These were primarily gold or copper,
though possibly some original genius may have happened upon a bit of
meteoric iron and pounded it out into a sword. But when man found that
the red ocher he had hitherto used only as a cosmetic could be made to
yield iron by melting it with charcoal he opened a new era in
civilization, though doubtless the ocher artists of that day denounced
him as a utilitarian and deplored the decadence of the times.

Iron is one of the most timid of metals. It has a great disinclination
to be alone. It is also one of the most altruistic of the elements. It
likes almost every other element better than itself. It has an especial
affection for oxygen, and, since this is in both air and water, and
these are everywhere, iron is not long without a mate. The result of
this union goes by various names in the mineralogical and chemical
worlds, but in common language, which is quite good enough for our
purpose, it is called iron rust.

[Illustration: By courtesy _Mineral Foote-Notes_.

From Agricola's "De Re Metallica 1550." Primitive furnace for smelting
iron ore.]

Not many of us have ever seen iron, the pure metal, soft, ductile and
white like silver. As soon as it is exposed to the air it veils itself
with a thin film of rust and becomes black and then red. For that reason
there is practically no iron in the world except what man has made. It
is rarer than gold, than diamonds; we find in the earth no nuggets or
crystals of it the size of the fist as we find of these. But
occasionally there fall down upon us out of the clear sky great chunks
of it weighing tons. These meteorites are the mavericks of the universe.
We do not know where they come from or what sun or planet they belonged
to. They are our only visitors from space, and if all the other spheres
are like these fragments we know we are alone in the universe. For they
contain rustless iron, and where iron does not rust man cannot live, nor
can any other animal or any plant.

Iron rusts for the same reason that a stone rolls down hill, because it
gets rid of its energy that way. All things in the universe are
constantly trying to get rid of energy except man, who is always trying
to get more of it. Or, on second thought, we see that man is the
greatest spendthrift of all, for he wants to expend so much more energy
than he has that he borrows from the winds, the streams and the coal in
the rocks. He robs minerals and plants of the energy which