Features
Did a Meteorite Strike the Crawfordsville Ford?
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...
Vacuum Tubes in Industry
A New Use for Radium
Radio Goes Man-Hunting
New Temperature Measurements of the Sun, Moon, Mars
Chicago's 'Madison Square Garden'
Butterfly Farming
When Locomotives Go to Sea
A Machine Age 'Milk Maid'
Centrifugally-Spun Concrete Piles
Mass Production of Preserved Food
Salt Making in India
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
