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World Resources and the World Middle Class

Economic development means entry into the high-consumption world middle class. In view of the limits that are set by world resources, only new scientific and technical knowledge can accelerate the rate of entry...

By Nathan Keyfitz

A Natural Fission Reactor

Two billion years ago in west Africa a rich deposit of uranium ore began operating as a nuclear reactor. Long dormant but preserved intact, the reactor came to light during the mining of the deposit...

By George A. Cowan

Interactions between Hormones and Nerve Tissue

Steroid hormones secreted by the gonads and the adrenal cortex can be traced to target cells in the brain. In the newborn animal the sex hormones help to lay down brain circuits that control later behavior...

By Bruce S. McEwen

The Direct Reduction of Iron Ore

Methods of making steel without smelting ore in a blast furnace are becoming increasingly economic where steelmaking facilities of modest scale are needed, notably in the developing countries...

By Jack Robert Miller

The Geometry of Soap Films and Soap Bubbles

The possible configurations they can form are governed by a few elementary rules that have been known for more than a century. A new mathematical model provides a sound basis for those rules...

By Frederick J. Almgren and Jean E. Taylor


These small marine animals build themselves a gossamer house out of mucus. The house incorporates an elaborate apparatus for filtering food particles out of the seawater

By Alice Alldredge

Polarized-Light Navigation by Insects

Experiments demonstrate that bees and ants find their way home by the polarization of the light of the sky. The detection system insects have evolved for the purpose is remarkably sophisticated...

By Rudiger Wehner

Canals in America

They did much to open up the interior of the new United States. Although inland waterways still play a major role, the original canal boom quickly came to an end with the rise of the railroads...

By John S. McNown


  • 50 and 100 Years Ago, July 1976

  • Science and the Citizen, July 1976

  • Letters

    Letters to the Editors, July 1976

  • Recommended

    Books, July 1976

  • Mathematical Recreation

    Mathematical Games, July 1976

  • Departments

    The Authors, July 1976

  • Bibliography, July 1976

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