Now times have changed. Projections of

 materials adequacy are available for periods extending

 some thirty years into the future, with longer range

 projections extending part way into the next century--

 very short periods when compared to the several thousand

 years over which human history extends, or even to the

 two centuries during which the United States has

 existed as a nation. And yet, even that limited

 perspective reveals a worsening minerals situation for

 the United States.

 In a study of America's resource needs conducted

 by Resources for the Future, Inc. in 1964, projections

 were made of expected metals requirements through the

 year 2000. Some of the results are summarized in

 Table 3. According to these projections, if lower

 grades of ore are used, domestic supplies of iron

 will be adequate to the end of the century; the adequacy

 of copper is questionable; and the domestic reserves

 of most of the rest are inadequate.

 The days when America could depend upon her

own supplies of minerals have ended, and the United

States must henceforth look to the rest of the world.

But other expanding world economies probably will

require great amounts ofminerals as well, and world

mineral supplies are not limitless. Under these

circumstances, the ability of the United States and

other nations to experience rapid rates of growth

indefinitely must be questioned.