First, the amount of iron remaining in the ground is very uncertain. It
may be more, or it may be less, than the present estimate.

Second, if the estimates are nearly correct, and if the present rate of
increase continues, all the high-grade ores will be exhausted by the
time the small boys of to-day are the business men of the nation.

Third, the best methods of reducing the drain on the supply are, (a) The
use of old iron as a mixture; (b) Carrying a part of the freight by
water to reduce the amount of iron required by the railroads; (c) The
larger use of concrete and cement to take the place of steel in
buildings; (d) Lessening the amount used for war; (e) The use of alloys.
This opens a large and promising field for invention. (f) More care in
preserving articles made of iron. This is a practical thing for every
person in our country to do. Every farm implement, or tool, that stands
out in the rain or is left without shelter during the winter, every
article carelessly lost or broken, has its part in making conditions
worse. All that are well cared for help to make the iron supply last a
little longer.

REFERENCES

Iron and Steel at Home and Abroad. (Andrew Carnegie.)

Conservation of Ores and Related Minerals. (Carnegie.) Report Governor's
Conference.

Report National Conservation Commission.

Reports Geological Survey.

Mineral Resources of the U. S. in 1908. Advance chapters available.

CHAPTER VIII

OTHER MINERALS

GOLD

Iron, in its usefulness to man, stands in a class to itself; but there
are dozens of other minerals that have their part in the comfort and
convenience of our daily life. Most of these, however, are found in
comparatively small quantities and have few uses.

The minerals which are in constant use by nearly all people and that are
found abundantly in the United States, are gold, silver, copper, lead,
zinc, and the elements used in manufacturing building materials.

Gold is valuable chiefly because it has been made the standard of money
value of the world. Africa produces one-third of the world's supply,
next come the United States and Australia, producing almost equal
amounts, Russia and Canada each produce a limited amount, and various
other countries together produce about one-sixteenth of the whole. (In
the statements of the gold supply of the United States the territory of
Alaska is included.)

Gold is not found alone but contained in quartz rock or sand. The m