t of the world's mineral production
is available for export beyond the countries of origin. Of this
exportable surplus the United States has about 40 per cent, consisting
principally of coal, copper, and formerly petroleum.

The value of the United States annual mineral production in recent years
has been from about $3,500,000,000 to $5,500,000,000. Annual imports of
mineral products into the United States have averaged recently in the
general vicinity of $450,000,000, the larger items being copper, tin,
fertilizers, petroleum, gems and precious stones, manganese, nickel, and
tungsten.

Again the perspective is changed when the value of water resources is
considered. As a physiologically indispensable resource, the value of
water in one sense is infinite. There is no way of putting an accurate
value on the total annual output used for drinking and domestic
purposes,--although even here some notion of the magnitude of the
figures involved may be obtained by considering the average per capita
cost of water in cities where figures are kept, and multiplying this
into the world population. This calculation would not imply that any
such amount is actually paid for water, because the local use of
springs, wells, and streams can hardly be figured on a cash basis; but,
if human effort the world over in securing the necessary water is about
as efficient as in the average American city, the figures would indicate
the total money equivalent of this effort.

SIGNIFICANCE OF GEOGRAPHIC DISTRIBUTION OF MINERAL PRODUCTION

The remarkable concentration of the world's mining and smelting around
the North Atlantic basin, indicated by the foregoing figures, does not
mean that nature has concentrated the mineral deposits here to this
extent. It is an expression rather of the localized application of
energy to mineral resources by the people of this part of the world. The
application of the same amount of energy in other parts of the world
would essentially change the distribution of current mineral production.
The controlling factor is not the amount of minerals present in the
ground; this is known to be large in other parts of the world and more
will be found when necessary. Controlling factors must be looked for in
historical, ethnological, and environmental conditions. This subject is
further discussed in the chapters on the several resources, and
particularly in relation to iron and steel.

THE INCREASING RATE OF PRODUCTION