This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
91. The directions given in Arts. 49 to 55, for running wires, apply to bellwork in some degree, but, in this work, the wires may be laid side by side, provided they are properly insulated. All wires should be concealed, running them under molding or behind the baseboards of rooms or hallways, when convenient. When it is necessary to cross a room, it is the best practice to run parallel with the joists under the floor; but, when the wire must run across the joists, fishing must be resorted to. The method employed is illustrated in Fig. 71. The joists j are located, and diagonal holes are bored through the floor on each side, through which the wires are drawn by means of a fishing wire, which is a steel ribbon made specially for this purpose.
92. When a push button is to be placed on a double partition, a 3/8-inch hole is drilled at that point, and a weighted line is dropped through in the intervening space. The line is then fished out at the floor level, and the wire attached. By the exercise of patience and ingenuity, it is possible to wire an old building in such a manner that there will be no trace visible of the wiring. All holes used in fishing should be filled with wooden plugs after the wires are in place.