it was to be
found only as a curiosity in the chemical laboratories. The discovery
that the metal could be extracted cheaply from cryolite, a mineral with
an aluminium base, obtained from Ivigtut, Greenland, led to a sparing
use of the metal in the economic arts.

The chief step in the production of the metal dates from the time that
the mineral _bauxite_, a hydroxide of aluminium and iron, was decomposed
in the electric furnace. The process has been repeatedly improved, and
under the patents covered by the Hall process the crude metal is now
produced at a market price of about eighteen cents per pound. The entire
production of the United States is controlled by the Pittsburg Reduction
Company, which also manufactures much of the commercial product of
England. The competitor of the Pittsburg Reduction Company is an
establishment in Germany, near Bremen.

Aluminium does not corrode; it is easily rolled, drawn, or cast; and,
bulk for bulk, it is less than one-third as heavy as copper. Because of
these properties it has a great and constantly growing economic value.
Because of its greater size, a pound of aluminium wire will carry a
greater electric current than a pound of copper wire of the same length.
It therefore has an increasing use as a conductor of electricity.

Bauxite, the mineral from which the metal is now chiefly extracted, is
obtained in two localities. One extends through Georgia and Alabama;
the other is in Arkansas.

=Lead.=--Lead is neither so abundant nor so widely diffused as iron,
copper, and the precious metals, but the supply is fully equal to the
demand. Lead ores, mainly galena or lead sulphide, occur abundantly in
the Rocky Mountains, Colorado, Idaho, and Utah, producing more than half
the total output of the United States. In these localities, in Mexico,
and in the Andean states of South America it is used mainly in the
smelting of silver ores.

Metallic lead is used largely in the manufacture of water-pipes, and for
this purpose it must be very nearly pure. It is also rolled into sheets
to be used as lining for water-tanks. The fact that the edges of
sheet-lead and the ends of pipes may be readily joined with solder gives
to lead a great part of its economic value. Alloyed with arsenic it is
used in making shot; alloyed with antimony it forms type metal; alloyed
with tin it forms pewter and solder.

The greater part, however, is manufactured into the carbonate or "white"
lead that is use