ct; but
during the war it became necessary to accept almost any kind of coal,
with a resulting net loss in quantity and in grade of output.

For a considerable number of mineral resources, such as the
ferro-alloys, foreign sources of supply were cut off during the war,
requiring the development and use, at high cost, of low-grade scattered
supplies in the United States. It was found possible to produce enough
chromite in the United States for domestic requirements, but at two or
three times the normal price of imported chromite. The grade was low and
the loss in efficiency to the consuming interests was a high one. The
extremely limited natural supplies were raided almost to the point of
exhaustion.

With the post-war resumption of importation of minerals of this kind,
producers naturally began a fight for a protective tariff, and the
question is yet unsettled. The tariff, if enacted, would in most cases
have to be a high one in order to permit the use of domestic supplies.
The results would be a large increase in cost to other industries,
decreased efficiency, and the early exhaustion of limited supplies in
this country. Most of the mineral resources have been concentrated by
nature in a comparatively few places in the world; and when the two
elements of conservation are considered--the materials themselves and
the human energy expended in obtaining and using them--it is clear that
any measure which interferes with the natural distribution of the
favored ores is anti-conservational from the world standpoint.

CONSERVATION OF COAL

In the sections on mineral resources, there are many casual references
to conservation of specific minerals. Here we shall not go further than
to introduce a brief discussion of the conservation of coal as
illustrative of the general problem of conservation of mineral
resources.

It has been estimated that the United States possesses, to a depth of
3,000 feet, in beds 14 inches or over, 3,538,554,000,000 tons of coal,
and an additional reserve between 3,000 and 6,000 feet of
666,600,000,000 tons.[42] If all the unmined coal to a depth of 3,000
feet could be placed in one great cubic pile, the pile would be 18 miles
long, 18 miles wide, and 18 miles high. Of the original amount of coal
to this depth only about 0.4 of 1 per cent has been mined or wasted in
mining. The wastage is estimated at about 50 per cent. If the annual
production of coal were to remain the same as in recent years,