ot yet utilized to any large extent. The minerals of South
America and Africa are in a very early stage of development. The total
world reserves will of course not be known until exploration and
development of the world's resources are complete--a time which will
probably never come. Figures of reserves represent only our present
partial state of knowledge and are likely to be considerably modified in
the future. Furthermore, the quantitative accuracy of knowledge of
reserves is so variable in different parts of the world that it is
almost impossible to make up world figures which have any great
validity. There are, however, certain broad facts ascertainable.

Every country in the globe is deficient in supplies of some minerals.
The United States is better off than any other country, but still lacks
many mineral commodities (see pp. 396-399.) No single continent has
sufficient reserves of all mineral commodities.

For the world, however, it may be stated with reasonable certainty that
the reserves of the principal minerals are now known to be ample with
the exception of those of oil, tin, and perhaps gold and silver. By
_ample_ we mean sufficient to give no cause for worry for the next few
decades. For many mineral commodities the amounts now actually in sight
will not last long, but the possibilities of extension and discovery are
so great that a long future availability of these commodities can be
counted upon with reasonable safety.

The present shortages in oil, tin, and other minerals mentioned may be
only temporary. There is a large part of the world still to be explored,
and the present reserves merely mark a stage in this exploration.
Nevertheless, the ratio of reserves and discovery on the one hand to
accelerated use on the other gives cause for much concern. Looking
forward to the future, the problem of mineral reserves in general is not
one of the possible ultimate amount which the earth may
contain--presumably in no case is this deficient--but of the success
with which the resource may be found and developed to keep up with the
rapid acceleration of demand. In the chapter on conservation the
suggestion is made that future difficulties are more likely to arise
from failure to coodinate the dynamic factors of supply and demand, than
from absolute shortage of material in the earth.

FOOTNOTES:

[10] Bastin, Edson S., and McCaskey, H. D., The work on mineral
resources done by the U. S. Geological Survey: _M