[57] Illustrations by courtesy of the General Motors Truck Co.

[58] Illustrations by courtesy of Jacobs & Davies, Engineers.

[59] Illustrations by courtesy of Ford Motor Co.

[60] Courtesy of the Pennsylvania Railroad Co.

[61] Courtesy of the Pennsylvania Railroad Co.

[62] Courtesy of the Pennsylvania Railroad Co.

[63] Courtesy of the Pennsylvania Railroad Co.

[64] Courtesy of the Pennsylvania Railroad Co.

[65] Courtesy of the Pennsylvania Railroad Co.

[66] Courtesy of the General Electric Co.