metals constitute about five-sixths of the known elementary
bodies. They are distinguished by a peculiar luster, by their
opacity, and by their power of conducting heat and electricity.
With few exceptions, metals possess considerable specific
gravity, hardness and cohesion, and require a high degree of
heat to liquefy them. One, mercury, is liquid at ordinary
temperatures; and a very few, as sodium and potassium, are
lighter than water, which they decompose with such energy as to
The properties which characterize metals, and by
which distinctive qualities are shown, are tabulated on page 2.
The various figures are collected from a multitude of sources,
the best attainable.
The authorities often differ somewhat widely, but this can
be accounted for from the fact that few metals are obtained
pure. The peculiarities in the same metals obtained from
different localities are often unnoticed, and account for the
variable statements of the cohesion in the tables compiled by
those who have investigated the properties of metals and
published the results.
Iron and steel, though strictly alloys, are usually spoken
of by the mechanic as metals; and none are so valuable as these.
A few words on their origin and production will be read with
interest by all mechanicians who desire to learn the operations
involved in the manufacture of the materials which they are
constantly using, not only for the construction of every
description of mechanism, but also in the form of tools and
appliances by which rough metal is wrought to shape.
Pure metallic iron has but little commercial
use, and in this state is comparatively unknown ; it is when
combined with carbon, sometimes modified by other elements, that
pure iron becomes the iron of commerce, and is known as
malleable iron, steel, and cast iron, as the proportion of
carbon is increased.
Pure iron may be obtained by placing a mixture
of magnetic oxide of iron and fragments of commercial iron, such
as filings, in a crucible, and heating to a white heat - the
crucible being meanwhile covered.
The pure iron thus obtained is softer than ordinary soft
malleable iron; it is very tenacious and ductile, and its
malleability is not affected by heating and suddenly cooling.
Though it does not retain magnetism, its magnetic power is very
The more free from impurities, the higher will be the electrical
conductivity of the metal and the greater the heat required for
its fusion - admixture of carbon reducing the point at which
pure iron melts, which is but little below the melting-point of
Though unaffected by dry air at ordinary temperatures, iron,
when in a state of very fine division, is liable to spontaneous