largest amount of gas escaping. If there is no leak detected, the hole may be closed up. In closing the bar holes in pavement, the earth should be tamped in to within six or eight inches of the top, and the hole then poured full of a grout made of neat cement.

82. Repairing Leaky Cast Iron Mains. When the leaky main or service has been uncovered, the cause of the leak may be ascertained, and a remedy should be applied which would be a permanent one. In case it is just simply a lead joint which leaks, it may be re-calked. If, however, examination would convince the foreman that the leaky joint is caused by vibration of the pipe caused by heavy traffic on the street, the joint must not only be re-calked, but, in order to be a permanent job, a leak clamp as shown in the figure below, should be placed on the joint.

The rubber on these clamps allows for a certain amount of vibration. The same method should be pursued in case of a leaky cement joint with this exception: that in the case of a cement joint, the first string of yarn should be entirely cut out and the joint should be made all over. A leak which is too small to light may sometimes be detected by the condition of the soil around the joint, in such cases it being usually blue or blackish in color. The men should be cautioned not to use a light when looking for leaks but to depend on the sense of smell or soap and water. The flash from a light may travel for some distance and acting as a fuse to a body of mixed gas and air, cause an explosion, resulting in great damage. If a main is broken the escape of gas may be

stopped temporarily by putting either clay or soap into the crack. If the main must be left for some time without being permanently repaired, a temporary repair may be made by wrapping canvas or muslin saturated with white or red lead, around the main. If the break runs around the pipe and does not extend longitudinally, the repair may be made by a split sleeve. If the crack extends for some length along the main, the piece must be cut out and a new piece inserted. When a split sleeve is to be used, all dirt and rust must be scraped off the pipe for a distance of a foot on each side of the break, and if the pipe has settled it must be brought back to the proper grade and alignment. A strip of unbleached muslin, wide enough to cover the break with a margin of three or four inches on each side and long enough to completely wind around the pipe several times, is smeared with a putty made of white lead, or equal parts of white and red lead, and linseed oil, and wrapped tightly around the pipe over the break. This serves to entirely prevent the escape of gas while the job is being completed. A split sleeve, that is, a sleeve made in two pieces, each of them similar in size and shape to the pieces that would be obtained by splitting a solid sleeve along a plane containing both its axis and diameter and provided with longitudinal flanges by which they can be bolted together, is then applied so as to cover the pipe at the break and for at least three or four inches on each side of it. The joint between the split sleeve and the pipe can be satisfactorily made in various ways.

One method is to plaster the inside of each half of the sleeve with a layer of Portland cement, mixed neat, of sufficient thickness to insure the complete filling of the joint and the compacting of the cement without allowing the flanges to come face to face when the two parts are put over the pipe and drawn together by means of the bolts. Enough cement should squeeze out through the spaces between the flanges to fill them thoroughly; but if this does not occur the unfilled places can be pointed up, so that, when the job is completed and the cement has set, the two halves of the sleeve are joined together with a gas tight joint by the cement between the flanges.

Another method is to make the joints between the flanges gas tight by using strips of millboard that have been soaked in hot water until they have become soft enough to be squeezed into all the roughness of the faces of the flanges when the two halves of the sleeve are put in place, surrounding the pipe, and bolted together. The joint between the sleeve and the pipe is then made exactly as would be done in the case of a solid sleeve, using either lead or cement. The latter is preferable, unless the conditions are very much against its use, since making lead joints involves the carrying to every repair job of a furnace, lead-pot and ladle. Drawings of two styles of split sleeves, showing their dimensions and the number of bolts used, can be found in the Proceedings of the American Gas Light Association, Vol. XV., page 68, and page xiv. of the Appendix and also in the American Gas. Light Journal, Vol. LXIX., page 712, and Progressive Age, Vol. XVI., page 529.

When the break runs too far along the pipe to be properly covered by a split sleeve, it is necessary to cut out the damaged portion of the pipe, making the cuts at least 3" to 4" beyond the furthest point reached by the crack at each end, and replace it by a new piece. To do this, the main must be uncovered for a sufficient distance to enable bag holes of the proper size to be drilled and tapped far enough apart not to interfere with the work of putting in the new piece. The gas having been shut off by means of the bags inserted in these holes, the pipe is cut at the proper points, either with a pipe cutter or by the use of a diamond point and cold chisel, and a new piece of pipe of the required length cut and put in, a solid sleeve being used to make the joint where the two spigot ends come together. Before sliding the sleeve into place, the opening between the two spigot ends is covered by wrapping the pipe with unbleached muslin prepared and used as is done in connection with the repair by means of a split sleeve. Either lead or cement joints can be made in the bell and in the sleeve, but the use of cement is generally preferable, for the reasons stated above. (A. G. L. A.)

Should the leak be simply from a sand hole in the main or

because a bar has been driven through it, the hole may be tapped and a plug inserted.

83. Determining Cause of Corrosion. If the main should show signs of pitting or of corrosion, it would indicate that either the main is laid in ground which is filled with ashes or some other material the acid of which would affect the pipe, or else it would indicate that the main is subject to the action of electrolysis. If the pitting is caused by electrolysis, the metal will be found to be very soft around the pit marks, resembling carbon, and capable of being cut with either a knife or chisel. There is also a difference in the oxide.

The difference between the oxide of iron due to cinders, ashes, etc., and that due to electrolysis, can always be determined by drawing a piece of oxide across the unglazed edge of a piece of broken porcelain or across a 'streak' plate used by mineralogists.

"The oxide from electrolysis is always three-quarters oxide -the magnetic oxide (Fe,O,), and leaves a black mark or streak. The oxide due to rust, cinders, etc., is always the two-thirds oxide (FeO3), and leaves a red streak. The three-quarters rust never occurs in the street except through electrolysis." (O. Q. B.-No. 603-J. M. Morehead.)

But the surest way of determining is by taking electric measurements with a volt meter. In case it is determined that the leakage is caused by electrolysis, an expert should be called into consultation to determine the best way of minimizing the trouble.

84. Broken Service Connections. Oftentimes the main will be found broken where the service connection is made to the main; in this case it is advisable to put on a split sleeve and tap the service connection through the sleeve, connecting up the service again by means of a running thread, and the service should be carefully blocked. If the service is broken off at the main or should be pulled out of the tap hole, the hole should be drilled and tapped a larger size, and the service re-connected. In doing this work, the workmen should be very careful that the service and main are properly blocked before leaving. In case the leak is from a rusty service, the

service pipe would need to be renewed, and if the soil shows signs of the presence of ashes or other corroding material, the service should be protected by an application of one of the coatings enumerated under "Low Pressure Main Laying."

85. Thawing Out Frozen Ground. Broken mains usually occur in the winter, and the ground may be thawed out by means of coke fire or, if it is not advisable to use a fire, by digging out the ground to a depth of 3" or 4", throwing a barrel of unslacked lime into this hole, throwing some water on the lime and covering with some pieces of old carpet; or burlap or even dirt may be used. The heat from the slack of the lime will thaw out the ground to the depth of a foot or more. It is well to do this in the evening when leaving the job, and allow the lime to stand in the hole all night.

86. Putting Out a Fire. If the main is broken and the escaping gas has caught fire by some means, the fire may be extinguished by throwing a quantity of flour upon it. The larger the blaze the greater the quantity of flour needed.

Heavy Split Sleeve.

Vent Pipes for Leaks.

87. All gas companies should make a practice of overhauling the main line on any street which is about to be paved, and put it in first-class condition, re-calking or repairing any leaks which may be found, and replacing any defective pieces of main. In this connection it has been suggested that when this work is done, it is well to mark on the curb or at least make a record of the location of joints and, in order to facilitate the location of any future leakage, to run a 34 vent pipe from the joint to the curb and then up to the service of the ground where it is capped. The idea is, that should a leak develop on the street, by taking off the cap the leak can be readily located, and in that case the leak cannot be repaired at once, the vent pipe may be so