would be little left to show that man had ever learned to extract iron
from its ores. The old question, "What becomes of all the pins?" may be
as well asked of rails, pipes and threshing machines. The end of all
iron is the same. However many may be its metamorphoses while in the
service of man it relapses at last into its original state of oxidation.
To save a pound of iron from corrosion is then as much a benefit to the
world as to produce another pound from the ore. In fact it is of much
greater benefit, for it takes four pounds of coal to produce one pound
of steel, so whenever a piece of iron is allowed to oxidize it means
that four times as much coal must be oxidized in order to replace it.
And the beds of coal will be exhausted before the beds of iron ore.

If we are ever to get ahead, if we are to gain any respite from this
enormous waste of labor and natural resources, we must find ways of
preventing the iron which we have obtained and fashioned into useful
tools from being lost through oxidation. Now there is only one way of
keeping iron and oxygen from uniting and that is to keep them apart. A
very thin dividing wall will serve for the purpose, for instance, a film
of oil. But ordinary oil will rub off, so it is better to cover the
surface with an oil-like linseed which oxidizes to a hard elastic and
adhesive coating. If with linseed oil we mix iron oxide or some other
pigment we have a paint that will protect iron perfectly so long as it
is unbroken. But let the paint wear off or crack so that air can get at
the iron, then rust will form and spread underneath the paint on all
sides. The same is true of the porcelain-like enamel with which our
kitchen iron ware is nowadays coated. So long as the enamel holds it is
all right but once it is broken through at any point it begins to scale
off and gets into our food.

Obviously it would be better for some purposes if we could coat our
iron with another and less easily oxidized metal than with such
dissimilar substances as paint or porcelain. Now the nearest relative to
iron is nickel, and a layer of this of any desired thickness may be
easily deposited by electricity upon any surface however irregular.
Nickel takes a bright polish and keeps it well, so nickel plating has
become the favorite method of protection for small objects where the
expense is not prohibitive. Copper plating is used for fine wires. A
sheet of iron dipped in melted tin comes out coated with a