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

[37] Illustrations by courtesy of the Bethlehem Steel Co.

[38] Illustrations by courtesy of the Bethlehem Steel Co.

[39] Illustrations by courtesy of the Bethlehem Steel Co.

[40] Illustrations by courtesy of the Bethlehem Steel Co.

[41] Illustrations by courtesy of the Bethlehem Steel Co.

[42] Illustrations by courtesy of the Bethlehem Steel Co.

[43] Illustrations by courtesy of the Bethlehem Steel Co.

[44] Illustrations by courtesy of the Bethlehem Steel Co.

[45] Illustrations by courtesy of the Bethlehem Steel Co.

[46] Illustrations by courtesy of United Shoe Machinery Co.