ement will be radically supplanted, and when this valuable mineral
will be as completely superseded as the stone of the aborigines. With
all its apparent potency, it has its evident weaknesses; moisture is
everywhere at war with it, gases and temperature destroy its fiber and
its life, continued blows or motion crystallize and rob it of its
strength, and acids will devour it in a night. If it be possible to
eliminate all, or even one or more, of these qualities of weakness in
any metal, still preserving both quantity and quality, that metal will
be the metal of the future.

The coming metal, then, to which our reference is made is aluminum, the
most abundant metal in the earth's crust. Of all substances, oxygen is
the most abundant, constituting about one-half; after oxygen comes
silicon, constituting about one-fourth, with aluminum third in all the
list of substances of the composition. Leaving out of consideration the
constituents of the earth's center, whether they be molten or gaseous,
more or less dense as the case may be, as we approach it, and confining
ourselves to the only practical phase of the subject, the crust, we find
that aluminum is beyond question the most abundant and the most useful
of all metallic substances.

It is the metallic base of mica, feldspar, slate, and clay. Professor
Dana says: "Nearly all the rocks except limestones and many sandstones
are literally ore-beds of the metal aluminum." It appears in the gem,
assuming a blue in the sapphire, green in the emerald, yellow in the
topaz, red in the ruby, brown in the emery, and so on to the white,
gray, blue, and black of the slates and clays. It has been dubbed "clay
metal" and "silver made from clay;" also when mixed with any
considerable quantity of carbon becoming a grayish or bluish black "alum
slate."

This metal in color is white and next in luster to silver. It has never
been found in a pure state, but is known to exist in combination with
nearly two hundred different minerals. Corundum and pure emery are ores
that are very rich in aluminum, containing about fifty-four per cent.
The specific gravity is but two and one-half times that of water; it is
lighter than glass or as light as chalk, being only one-third the weight
of iron and one-fourth the weight of silver; it is as malleable as gold,
tenacious as iron, and harder than steel, being next the diamond. Thus
it is capable of the widest variety of uses, being soft when ductility,
fi