The Wonder Book of Knowledge / The Marvels of Modern Industry and Invention, the Interesting Stories of Common Things, the Mysterious Processes of Nature Simply Explained

by Unknown

Courtesy of the Bethlehem Steel Co.

[428]

Front Door, with Time Lock, for Armor Plate Safe Deposit Vault

Thickness of front door plate, 12¹⁄₂ inches; weight of door plate, 12,000 pounds.

Courtesy of the Bethlehem Steel Co.

[429]

Reproduced by permission of the Philadelphia Museums.

Casting Pig Iron