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

[17] Illustrations by courtesy of the McClure Co.

[18] Illustrations by courtesy of New York Edison Co., unless otherwise indicated.

[19] Illustrations by courtesy of The Curtis Publishing Co.

[20] Courtesy of George A. Hormel & Co.

[21] Courtesy of The Field, New York City.

[22] Courtesy of The Field, New York City.

[23] Courtesy of the California Redwood Association.

[24] Illustrations by courtesy of The Brunswick-Balke-Collender Co.

[25] Illustrations by courtesy of the American Pin Company.

[26] Illustrations by courtesy of the Common Sense Gum Co. Story by courtesy of the American Chicle Co. and the Common Sense Gum Co.