3/8 inch pipe, 26 feet, three burners. 1/2 inch pipe, 30 feet, six burners. 3/4 inch pipe, 50 feet, twenty burners. 1 inch pipe, 70 feet, thirty-five burners. 1-1/4 inch pipe, 100 feet, sixty burners. 1-1/2 inch pipe, 150 feet, one hundred burners. 2 inch pipe, 200 feet, two hundred burners. 2-1/2 inch pipe, 300 feet, three hundred burners. 3 inch pipe, 450 feet, four hundred and fifty burners, 3-1/2 inch pipe, 500 feet, six hundred burners. 4 inch pipe, 600 feet, seven hundred and fifty burners. (_e_) Machines of the carbide-feed type must not be fitted with continuous drain connexions leading to sewers, but must discharge into suitable open receptacles which may have such connections. (_f_) Piping must be thoroughly tested both before and after the burners have been installed. It must not show loss in excess of 2 inches within twelve hours when subjected to a pressure equal to that of 15 inches of mercury. (_g_) Piping and connexions must be installed by persons experienced in the installation of acetylene apparatus. 8. CARE AND ATTENDANCE.--In the care of generators designed for a lighting period of more than five hours always clean and recharge the generating chambers at regular stated intervals, regardless of the number of burners actually used. Where generators are not used throughout the entire year always remove all water and gas and clean thoroughly at the end of the season during which they are in service. It is usually necessary to take the bell portion out and invert it so as to allow all gas to escape. This should never be done in the presence of artificial light or fire of any kind. Always observe a regular time, during daylight hours only, for attending to and charging the apparatus. In charging the generating chambers of water-feed machines clean all residuum carefully from the containers and remove it at once from the building. Separate from the mass any unslacked carbide remaining and return it to the containers, adding now carbide as required. Be careful never to fill the containers over the specified mark, as it is important to allow for the swelling of the carbide when it comes in contact with water. The proper action and economy of the machine are dependent on the arrangement and amount of carbide placed in the generator. Carefully guard against the escape of gas. Whenever recharging with carbide always replenish the water-supply. Never deposit residuum or exhausted material from water-feed machines in sewer-pipes or near inflammable material. Always keep water-tanks and water-seals filled with clean water. Never test the generator or piping for leaks with a flame, and never apply flame to an outlet from which the burner has been removed. Never use a lighted match, lamp, candle, lantern or any open light near the machine. Failure to observe the above cautions is as liable to endanger life as property.