PIPES AND FITTINGS.--As a general rule it is unadvisable to use lead or composition pipe for permanent acetylene connexions. If exposed, it is liable to be damaged, and perhaps penetrated by a blow, and if set in the wall and covered with paper or panel it is liable to be pierced if nails or tacks should at any time be driven into the wall. There is also an increased risk in case of fire, owing to its ready fusibility. If used at all--and it has obvious advantages--lead or composition piping should be laid on the surface of the walls, &c., and protected from blows, &c., by a light wooden casing, outwardly resembling the wooden coverings for electric lighting wires. It has been a common practice, in laying the underground mains required for supplying the villages which are lighted by means of acetylene from a central works in different parts of France, to employ lead pipes. The plan is economical, but in view of the danger that the main might be flattened by the weight of heavy traction-engines passing over the roads, or that it might settle into local dips from the same cause or from the action of subterranean water, in which dips water would be constantly condensing in cold weather, the use of lead for this purpose cannot be recommended. Steam-barrel would be preferable to cast pipe, because permanently sound joints are easier to make in the former, and because it is not so brittle. The fittings used for acetylene must have perfectly sound joints and taps, for the same reasons that the service-pipes must be quite sound. Common gas-fittings will not do, the joints, taps, ball-sockets, &c., are not accurately enough ground to prevent leakage. They may in many cases be improved by regrinding, but often the plug and barrel are so shallow that it is almost impossible to ensure soundness. It is therefore better to procure fittings having good taps and joints in the first instance; the barrels should be long, fairly wide, and there should be no sensible "play" between plug and barrel when adjusted so that the plug turns easily when lightly lubricated. Fittings are now being specially made for acetylene, which is a step in the right direction, because, in addition to superior taps and joints being essential, smaller bore piping and smaller through-ways to the taps than are required for coal-gas serve for acetylene. It is perhaps advisable to add that wherever a rigid bracket or fitting will answer as well as a jointed one, the latter should on no account be used; also water-slide pendants should never be employed, as they are fruitful of accidents, and their apparent advantages are for the most part illusory. Ball-sockets also should be avoided if possible; if it is absolutely necessary to have a fitting with a ball-socket, the latter should have a sleeve made of a short length of sound rubber-tubing of a size to give a close fit, slipped over so as to join the ball portion to the socket portion. This sleeve should be inspected once a