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Earlier Maturation in Man

Over the past 100 years people have been not only getting bigger but also getting bigger earlier. By the same token there has been a dramatic decline in the age of puberty

By J. M. Tanner

The Beneficiation of Iron Ores

As North America's high-grade iron deposits approach exhaustion steel production increases. The apparent paradox is due largely to the development of ingenious ways to enrich lower-grade ores...

By M. M. Fine

How Proteins Start

The chain of amino acid units that constitutes a protein molecule begins to grow when a variant of one of the standard amino acids is delivered to the site of synthesis by a specific transfer agent...

By Brian F. C. Clark and Kjeld A. Marcker

Remote Sensing of Natural Resources

Several devices are now available to supplement the aerial camera in detecting natural resources from airplanes and spacecraft. They include radar, gamma ray detectors and sensors of infrared energy...

By Robert N. Colwell

The g Factor of the Electron

It is the index of the ratio of the electron's magnetic moment to its spin angular momentum. An interesting number in its own right, its precise measurement has had far-reaching implications...

By H. R. Crane

The Venous System

The veins constitute a reservoir for the blood supply, not merely a system of passive conduits. They constrict and dilate actively, thus maintaining a satisfactory distribution of blood in the body...

By J. Edwin Wood

The Circulation of the Sun's Atmosphere

A new hypothesis may explain how the sun can rotate faster at its equator than it does elsewhere. Analysis of sunspot movements has provided a clue to this 100-year-old mystery

By Victor P. Starr and Peter A. Gilman

Perpetual Motion Machines

Over the past 400 years numerous inventors have proposed marvelous ways of getting something for nothing. All these proposals have foundered on either the first or the second law of thermodynamics...

By Stanley W. Angrist


  • 50 and 100 Years Ago: January 1968

  • Science and the Citizen: January 1968

  • Letters

    Letters to the Editors, January 1968

  • Recommended


  • Mathematical Recreation

    Mathematical Games

  • Amateur Scientist

    The Amateur Scientist

  • Departments

    The Authors

  • Bibliography

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