[11] Ill.u.s.trations by courtesy of R. Hoe & Co.
[12] Ill.u.s.trations by courtesy of the A. I. Root Co.
[13] Ill.u.s.trations by courtesy of the Hotpoint Electric Heating Co.
[14] Ill.u.s.trations by the courtesy of the American Telephone and Telegraph Co.
[15] Ill.u.s.trations by courtesy of the Otis Elevator Co.
[16] Ill.u.s.trations by courtesy of the International Silver Co.
[17] Ill.u.s.trations by courtesy of the McClure Co.
[18] Ill.u.s.trations by courtesy of New York Edison Co., unless otherwise indicated.
[19] Ill.u.s.trations 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 a.s.sociation.
[24] Ill.u.s.trations by courtesy of The Brunswick-Balke-Collender Co.
[25] Ill.u.s.trations by courtesy of the American Pin Company.
[26] Ill.u.s.trations by courtesy of the Common Sense Gum Co. Story by courtesy of the American Chicle Co. and the Common Sense Gum Co.
[27] Ill.u.s.trations by courtesy of The Brunswick-Balke-Collender Co.
[28] Ill.u.s.trations by courtesy of the Addressograph Co.
[29] Ill.u.s.trations by courtesy of the Pyrene Manufacturing Co.
[30] Ill.u.s.trations by courtesy of Gatchel & Manning.
[31] Courtesy of Mr. Charles L. Trout.
[32] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[33] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[34] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[35] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[36] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[37] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[38] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[39] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[40] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[41] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[42] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[43] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[44] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[45] Ill.u.s.trations by courtesy of the Bethlehem Steel Co.
[46] Ill.u.s.trations by courtesy of United Shoe Machinery Co.
[47] Courtesy of James Boyd & Bro., Inc.
[48] Courtesy of American LaFrance Fire Engine Co.
[49] Courtesy of American LaFrance Fire Engine Co.
[50] Courtesy of American LaFrance Fire Engine Co.
[51] Courtesy of American LaFrance Fire Engine Co.
[52] Ill.u.s.trations by courtesy of American Cyanamid Company.
[53] Courtesy of The Strauss Bascule Bridge Co.
[54] Courtesy of The American Magazine.
[55] _Ill.u.s.trations by courtesy of the Railway Age Gazette and Standard Steel Car Co._
[56] Ill.u.s.trations by courtesy of Diamond Crystal Salt Co.
[57] Ill.u.s.trations by courtesy of the General Motors Truck Co.
[58] Ill.u.s.trations by courtesy of Jacobs & Davies, Engineers.
[59] Ill.u.s.trations by courtesy of Ford Motor Co.
[60] Courtesy of the Pennsylvania Railroad Co.