2. The generator should have an efficiency of not less than 90 per cent., which, with carbide yielding 5 cubic feet per pound, would imply a yield of 4.5 cubic feet for each pound of carbide used. 3. The size of the pipes carrying the gas should be proportioned to the maximum rate of generation, so that undue back pressure from throttling may not occur. 4. The carbide should be completely decomposed in the apparatus, so that lime sludge discharged from the generator shall not be capable of generating more gas. 5. The pressure in any part of the apparatus, on the generator side of the holder, should not exceed that of 20 inches of water, and on the service side of same, or where no gasholder is provided, should not exceed that of 5 inches of water. 6. The apparatus should give no tarry or other heavy condensation products from the decomposition of the carbide. 7. In the use of a generator regard should be had to the danger of stoppage of passage of the gas and resulting increase of pressure which may arise from the freezing of the water. Where freezing may be anticipated, steps should be taken to prevent it. 8. The apparatus should be so constructed that no lime sludge can gain access to any pipes intended for the passage of gas or circulation of water. 9. The use of glass gauges should be avoided as far as possible, and, where absolutely necessary, they should be effectively protected against breakage. 10. The air space in a generator before charging should be as small as possible. 11. The use of copper should be avoided in such parts of the apparatus as are liable to come in contact with acetylene. The BRITISH ACETYLENE ASSOCIATION has drawn up the following list of regulations which, it suggests, shall govern the construction of generators and the installation of piping and fittings: 1. Generators shall be so constructed that, when used in accordance with printed instructions, it shall not be possible for any undecomposed carbide to remain in the sludge removed therefrom. 2. The limit of pressure in any part of the generator shall not exceed that of 20 inches of water, subject to the exception that if it be shown to the satisfaction of the Executive of the Acetylene Association that higher pressures up to 50 inches of water are necessary in certain generators, and are without danger, the Executive may, with the approval of the Home Office, grant exemption for such generators, with or without conditions. 3. The limit of pressure in service-pipes, within the house, shall not exceed 10 inches of water.