Chicago : Engineering and Contracting Pub. Co. · leaf 80
cates the cause July 19, 1911. ENGINEERING & CONTRACTING 65 which has led to the progressive increase inthe economy and speed of tunnel-construction. The advance of the heading or pilot—ir-respective of whether it be driven top or bot-tom—is the factor controlling the rate of ad-vance, as,… … Fig. 1—Loetchberg Tunnel Carriage BroughtForward After Mucking.
Buildings
Internet Archive · University of Illinois Urbana-Champaign · Public Domain Mark 1.0. Free to use for anything.
