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 147
••■■■■■■ ^- ■ ^ ■ ••■■• EARTH ■ -ZFtET »l Fig. 983.—Cross section of wrought iron pipe conduit laid in hydraulic cement. … The pipe connections consist of a taper screw thread coupling whichcan be easily made up as the pipes are laid, and which forms a tight joint. The pipes in each tier are usually laid from J/2 to ^4 of their diameterapart, and when the first tier is in place, the spaces between and aroundthe pipes…
Electrical engineering
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