73
Throughout the past century, minerals have tended
to be used with increasing efficiency. Greater efficiency
in fuel use, as is commonly known, has greatly increased
the amount of work that can be performed by burning a
ton of coal or a gallon of oil. Similar increases in
production per ton of iron and copper have occurred as
a result of improvements in the quality of the metals
themselves, and of changes in metals markets, and in the
4l
complexity of final products. Greater production per
ton of new metal also has resulted from the recovery of
old scrap and from the substitution of other materials
for iron and copper in some processes. Each of these
influences will be considered in turn.
Improvements in quality have been particularly
b2
important to iron and steel.
As a matter of fact, it is rather misleading to
talk simply about "steel," This term may have
been justified in the early days of the industry
when plain carbon steel was its chief product,
but today there is actually a large family of
steels covering a wide variety of useful prop
erties. Many of these steels are tailor-made
for a particular application. As one example,
silicon steels are specially designed to allow the
maker of electrical machinery to take full advantage
of their unique electrical and magnetic qualities.
Again, special alloy steels of high toughness at
41
Production of steel ingots per $1^60 billions
of durable goods and construction fell from .93 million
tons in 1929 to .65 million tons in i960. See Landsberg,
Resources in America's Future, p. 890, Table A16-21.
42
This has been true in other industries as well.
Cf. William Woodruff, "Growth of the Rubber Industry of
Great Britain and the United States," Journal of Economic
His to ry, XV (December, 1935) > 376-91*