does crack, the iron
beneath is not so apt to rust and scale off the coating.

These, then, are some of the methods which are now being used to combat
our eternal enemy, the rust that doth corrupt. All of them are useful in
their several ways. No one of them is best for all purposes. The claim
of "rust-proof" is no more to be taken seriously than "fire-proof." We
should rather, if we were finical, have to speak of "rust-resisting"
coatings as we do of "slow-burning" buildings. Nature is insidious and
unceasing in her efforts to bring to ruin the achievements of mankind
and we need all the weapons we can find to frustrate her destructive
determination.

But it is not enough for us to make iron superficially resistant to rust
from the atmosphere. We should like also to make it so that it would
withstand corrosion by acids, then it could be used in place of the
large and expensive platinum or porcelain evaporating pans and similar
utensils employed in chemical works. This requirement also has been met
in the non-corrosive forms of iron, which have come into use within the
last five years. One of these, "tantiron," invented by a British
metallurgist, Robert N. Lennox, in 1912, contains 15 per cent. of
silicon. Similar products are known as "duriron" and "Buflokast" in
America, "metilure" in France, "ileanite" in Italy and "neutraleisen" in
Germany. It is a silvery-white close-grained iron, very hard and rather
brittle, somewhat like cast iron but with silicon as the main additional
ingredient in place of carbon. It is difficult to cut or drill but may
be ground into shape by the new abrasives. It is rustproof and is not
attacked by sulfuric, nitric or acetic acid, hot or cold, diluted or
concentrated. It does not resist so well hydrochloric acid or sulfur
dioxide or alkalies.

The value of iron lies in its versatility. It is a dozen metals in one.
It can be made hard or soft, brittle or malleable, tough or weak,
resistant or flexible, elastic or pliant, magnetic or non-magnetic, more
or less conductive to electricity, by slight changes of composition or
mere differences of treatment. No wonder that the medieval mind ascribed
these mysterious transformations to witchcraft. But the modern
micrometallurgist, by etching the surface of steel and photographing it,
shows it up as composite as a block of granite. He is then able to pick
out its component minerals, ferrite, austenite, martensite, pearlite,
graphite, cementite, a