SERVICE-PIPES AND MAINS.--The pipes used for the distribution of acetylene must be sound in themselves, and their joints perfectly tight. Higher pressures generally prevail in acetylene service-pipes within a house than in coal-gas service-pipes, while slight leaks are more offensive and entail a greater waste of resources. Therefore it is uneconomical, as well as otherwise objectionable, to employ service-pipes or fittings for acetylene which are in the least degree unsound. Unfortunately ordinary gas-barrel is none too sound, nor well-threaded, and the taps and joints of ordinary gas-fittings are commonly leaky. Hence something better should invariably be used for acetylene. What is known as "water" barrel, which is one gauge heavier than gas-barrel of the same size, may be adopted for the service-pipes, but it is better to incur a slight extra initial expense and to use "steam" barrel, which is of still heavier gauge and is sounder than either gas or water-pipe. All elbows, tees, &c., should be of the same quality. The fitters' work in making the joints should be done with the utmost care, and the sloppy work often passed in the case of coal-gas services must on no account be allowed. It is no exaggeration to say that the success of an acetylene installation, from the consumer's point of view, will largely, if not principally, depend on the tightness of the pipes in his house. The statement has been made that the "paint" used by gas-fitters, _i.e._, the mixture of red and white lead ground in "linseed" oil, is not suitable for employment with acetylene, and it has been proposed to adopt a similar material in which the vehicle is castor-oil. No good reason has been given for the preference for castor-oil, and the troubles which have arisen after using ordinary paint may be explained partly on the very probable assumption that the oil was not genuine linseed, and so did not dry, and partly on the fact that almost entire reliance was placed on the paint for keeping the joint sound. Joints for acetylene, like those for steam and high-pressure water, must be made tight by using well-threaded fittings, so as to secure metallic contact between pipe and socket, &c.; the paint or spun-yarn is only an additional safeguard. In making a faced joint, washers of (say, 7 lb) lead, or coils of lead-wire arc extremely convenient and quite trustworthy; the packing can be used repeatedly.