(6) Put a piece of finely grained emery paper half the size of a postage stamp in a place where it will wear away rotating brushes. The emery paper and the motor will be destroyed in the resulting fire. (7) Sprinkle carbon, graphite or metal dust on slip-rings so that the current will leak or short circuits will occur. When a motor is idle, nick the slip-rings with a chisel. (8) Cause motor stoppage or inefficiency by applying dust mixed with grease to the face of the armature so that it will not make proper contact. (9) To overheat electric motors, mix sand with heavy grease and smear it between the stator and rotor, or wedge thin metal pieces between them. To prevent the efficient generation of current, put floor sweepings, oil, tar, or paint between them. (10) In motors using three-phase current, deeply nick one of the lead-in wires with a knife or file when the machine is at rest, or replace one of the three fuses with a blown-out fuse. In the first case, the motor will stop after running awhile, and in the second, it will not start. (f) Transformers (1) Transformers of the oil-filled type can be put out of commission if you pour water, salt water, machine-tool coolant, or kerosene into the oil tank. (2) In air-cooled transformers, block the ventilation by piling debris around the transformer. (3) In all types of transformers, throw carbon, graphite or metal dust over the outside bushings and other exposed electrical parts. (g) Turbines for the most part are heavily built, stoutly housed, and difficult of access. Their vulnerability to simple sabotage is very low. (1) After inspecting or repairing a hydro turbine, fasten the cover insecurely so that it will blow off and flood the plant with water. A loose cover on a steam turbine will cause it to leak and slow down. (2) In water turbines, insert a large piece of scrap iron in the head of the penstock, just beyond the screening, so that water will carry the damaging material down to the plant equipment. (3) When the steam line to a turbine is opened for repair, put pieces of scrap iron into it, to be blasted into the turbine machinery when steam is up again. (4) Create a leak in the line feeding oil to the turbine, so that oil will fall on the hot steam pipe and cause a fire. (h) Boilers (1) Reduce the efficiency of steam boilers any way you can. Put too much water in them to make them slow-starting, or keep the fire under them low to keep them inefficient. Let them dry and turn the fire up; they will crack and be ruined. An especially good trick is to keep putting limestone or water containing lime in the boiler; it will deposit lime on the bottom and sides. This deposit will provide very good insulation against heat; after enough of it has collected, the boiler will be completely worthless. (3) _Production. Metals_ (a) Iron and Steel