Robert H. McDormick; “The Eighteenth St. Sewer Explosion at Detroit;” Engineering News; February 12, 1914; p. 373.


18 Feb 1915 advertisement in Engineering News for a new tunneling machine … for use in clay, stiff sand, and gravel formations. Note that the source of machine’s power is an electric motor. Carpenter Construction Co. Document provided courtesy of Jon Schladweiler
PDF version.