If one plans using electricity for heavy-duty stoves, such as ranges and radiators, it is necessary to install a separate heating circuit. This is the best procedure in any event, even when the devices are all small and suited to lamp circuits. The wire used can be determined by referring to the table for carrying capacity, under the column headed "rubber-covered." A stove or range drawing 40 amperes, would require a No. 4 wire, in moulding. A good plan is to run the heating circuit through the basement, attaching it to the rafters by means of porcelain knobs. Branches can then be run up through the floor to places where outlets are desired. Such a branch circuit should carry fuses suitable to the allowed carrying capacity of the wire. _Knob and Cleat Wiring_ Knob and cleat wiring, such as is used extensively for barns and out-buildings, requires little explanation. The wires should not be closer than 2-1/2 inches in open places, and a wider space is better. The wires should be drawn taut, and supported by cleats or knobs at least every four feet. In case of branch circuits, one wire must be protected from the other it passes by means of a porcelain tube. It should never be used in damp places, and should be kept clear of dust and litter, and protected from abrasion. [Illustration: Knob and cleat wiring] Knob and tube wiring is frequently used in houses, being concealed between walls or flooring. In this case, the separate wires are stretched on adjoining beams or rafters, and porcelain tubes are used, in passing through cross beams. For a ceiling or wall outlet, a spliced branch is passed through the plaster by means of porcelain tubes or flexible loom. Wires from the house to the barn should be uniform with transmission wires. At the point of entry to buildings they must be at least six inches apart, and must take the form of the "drop loop" as shown in the illustration. A double-pole entrance switch must be provided, opening downward, with a double-pole fuse. In passing over buildings wires must not come closer than 7 feet to flat roofs, or one foot to a ridge roof. Feed-wires for electric motors should be determined from the table of safe carrying capacities, and should be of liberal size. CHAPTER IX THE ELECTRIC PLANT AT WORK Direct-connected generating sets--Belt drive--The switchboard--Governors and voltage regulators--Methods of achieving constant pressure at all loads: Over-compounding the dynamo; A system of resistances; (A home-made electric radiator); Regulating voltage by means of the rheostat--Automatic devices--Putting the plant in operation.