[=Wires; how placed in rooms.=] Positive machine feed wires, when extended into rooms, shall be placed not nearer than four feet of the track, where the room is of sufficient width, and the same shall only be connected to the positive wire or wires on the entry while in actual use. The material used for making such connection shall be of sufficient length to reach across the entry, and when same is disconnected, it shall be kept with the machine operating at such point or working place. No electric wires shall be extended into any room unless a one hundred and fifty foot cable will not reach the face of the room, and then not beyond the outside corner of the last breakthrough. [=Protection of terminal ends.=] All terminal ends of positive wires shall be guarded so as to prevent persons inadvertently coming in contact therewith. [=Connection of negative wires, pipe lines and track. Bonding of track.=] The bonded track, the negative wires and metallic pipe lines, when coming near each other, may be connected together at intervals not exceeding five hundred feet, and any track used as the return or earth system shall be properly bonded. In no case shall a pipe line, or any part thereof, be used exclusively as the return, and when connected to the earth system, the negative wire or bonded track shall be of ample capacity, exclusive of the pipe line, to carry the current. [=Trolley wires; how erected.=] The trolley wire shall be carried upon hangers or other fixtures which will properly insulate it from contact with the roof or other substances, and so the trolley wheel can trail without the necessity of being constantly attended for that purpose, and no trolley shall be run on any wire not so carried. [=Locomotive must not be operated improperly.=] No locomotive shall be operated by means of a person holding and sliding upon or frequently making contact with the positive wire with any device attached to the cable as a substitute for a trolley, but these provisions shall not prohibit the operation of a locomotive by means of a cable without the use of the trolley, provided the cable be connected to and disconnected from the positive wire when the locomotive is not in motion. [=Protection to machine cable crossing entry track.=] Means shall be provided by which machine runners may readily carry the machine cable from the machine to the feed wires on one side of the entry, either under or over the track rails, in the entry where such wires are located, and so the cable will not come in contact with such track rails, thereby reducing the danger of shock to persons or animals required to travel such entry, to the minimum. (Sec. 911, 948; Penalty, Sec. 976.)