The most satisfactory method of testing the soundness of gaspipes and fittings is to subject them to air pressure in excess of the pressure of the gas which will flow through them. All cocks having been carefully shut off, an ordinary pressure gauge is attached, by means of a piece of indiarubber tubing, to the nozzle of a gas bracket or pendant, and the cock turned on. Air is then forced into the main service pipe by means of an ordinary force pump provided with a stop-cock, until a pressure of about 4in. or 5 in. of water is shown on the pressure gauge, when the cock in communication with the force pump is shut off and the gauge care Tally watched. If all the fittings are sound, the level of the water in the pressure gauge will remain constant. If, on the contrary, there is the slightest leak, the liquid in the pressure gauge will gradually sink until it attains the same level in both limbs of the gauge.