(_f_) Must be provided with suitable vent connexions to the blow-off pipe so that residuum may be removed and the generating water replaced without causing siphoning or introducing air to the gasholder upon recharging. This applies to machines of the carbide-feed type. (_g_) Feed mechanism for machines of the carbide-feed type must be so designed that the direct fall of carbide from the carbide holder into the water of the generator is prevented at all positions of the feed mechanisms; or, when actuated by the rise and fall of a gas-bell, must be so arranged that the feed-valve will not remain open after the landing of the bell, and so that the feed valve remains inoperative as long as the filling opening on the carbide hopper remains open. Feed mechanisms must always be far enough above the water-level to prevent clogging from the accumulation of damp lime. For this purpose the distance should be not less than 10 inches. 17. CARBIDE CHAMBERS.--(_a_) Must be constructed of galvanised iron or steel not less than No. 24 U.S. Standard gauge in thickness for capacities up to and including 50 pounds and not less than No. 22 U.S. Standard gauge for capacities in excess of 50 pounds. (_b_) Must have sufficient carbide capacity to supply the full number of burners continuously and automatically during the maximum lighting period. This rule removes the necessity of recharging or attending to the machine at improper hours. Burners almost invariably require more than their rated consumption of gas, and carbide is not of staple purity, and there should therefore be an assurance of sufficient quantity to last as long as light is needed. Another important consideration is that in some establishments burners are called upon for a much longer period of lighting than in others, requiring a generator of greater gas-producing capacity. Machines having several generating chambers must automatically begin generation in each upon exhaustion of the preceding chamber. (_c_) Must be arranged so that the carbide holders or charges may be easily and entirely removed in case of necessity. 18. GASHOLDERS.--(_a_) Must be constructed of galvanised iron or steel not less than No. 24 U.S. Standard gauge in thickness for capacities up to and including 20 gallons, not less than No. 22 U.S. Standard gauge for capacities between 20 and 75 gallons, and not less than No. 20 U.S. Standard gauge for capacities in excess of 75 gallons. Gas-bells, if used, may be two gauges lighter than holders. Condensation chambers, if placed under holders, to be of same gauge as holders. (_b_) Must be of sufficient capacity to contain all gas generated after all lights have been extinguished. If the holder is too small and blows off frequently after the lights are extinguished there is a waste of gas. This may suggest improper working of the apparatus and encourage tampering.