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Features

The Eyes and Ears of the Railroad

By Francis X. Milholland

Did a Meteorite Strike the Crawfordsville Ford?

By Charles Clayton Wylie

New Light on Old Foods

Unique Solutions of Bridge Construction Problems

The heaviest lift span in the world, weighing 1580 tons, in the new bridge. The bridge proper has a clearance of 70 feet, but the great lift span can be opened to a clearance of 135 feet in only 85 seconds

By C. R. Harding

Vacuum Tubes in Industry

By Raymond Francis Yates

A New Use for Radium

By Robert F. Mehl

Radio Goes Man-Hunting

By W. M. J. Barkley

New Temperature Measurements of the Sun, Moon, Mars

By Henry Norris Russell

Chicago's 'Madison Square Garden'

Butterfly Farming

By Adeline Taylor

When Locomotives Go to Sea

A Machine Age 'Milk Maid'

By James A. Tobey

Centrifugally-Spun Concrete Piles

By L. R. Need

Mass Production of Preserved Food

Salt Making in India

By C. F. Strickland

Departments

  • Departments

    Across the Editor's Desk, April 1931

  • Back of Frontispiece, April 1931

  • The Red Fusee is a Signal to Stop

  • Our Point of View, April 1931

  • Large-Scale Insect Trapping, Synthetic Ham—What Next and more

  • Stocking Repair Method Patent Held Valid, "Kalas-Sill" Not Registrable as Trademark and more

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April 1931

Think Outside the Gift Box