Hawkins electrical guide. Questions, answers & illustrations; a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications; a practical treatise (1914)
Hawkins, N. (Nehemiah), 1833- · New York, T. Audel · leaf 143
enough strengthto withstand the pressure to which they are subjected, and are,therefore, very thin and liable to be quickly destroyed by UNDERGROUND WIRING 831 corrosion, but the ducts formed by them will always remainunimpaired in the hardened mass of concrete. Wooden Duct Conduits.—In this type… … Fig. 978.—Method of laying multiple duct vitrified clay conduit,by the dowel pins shown in the cut. The sections are centered to six feet long, with a round hole about three inches in diam-eter bored through them longitudinally. As shown by fig. 979a cylindrical projection is turned on one end of…
Electrical engineering
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