176

TAPPING PRESSURE MAINS.

wear and tear, and interest on Capital, in 1878, and a pro-portionately smaller amount for the years 1879 and 1880.As the amount of work done increased, the cost per 100 foot-tons diminished, and since at the time to which the Statementreferred the engines were not worked up to their full power,the cost would he probahly still further reduced.

At Cardiff Docks with ordinary engines worked up totheir full power, the cost (including fuel Stores and workingexpenses) was 3s. per 1000 cubic feet, equivalent to Orid. per100 foot-tons.

TAPPING PRESSURE MAINS.

An ingenious plan for tapping low pressure mains withoutcutting off the water has been devised by Mr. Morris. Thisis shown by fig. "41. X is the pipe to be tapped, and tohave a junction ferrule inserted, under pressure. H is apacking piece, which is first placed on the pipe over the pointwhere the hole is to be made, a layer of greased feit or othermaterial being laid between the two, to make a good joint.A saddle piece D is then fixed by means of a chain F. Aspindle A, with a drill tap B at its lower end, is inserted in thetop o£ the saddle piece. A socket E, having a leather washer atits lower end (to prevent leakage), has, resting in the top of it,the nut C, with arms for screwing in, and for unscrewing thesaddle screw. After the hole is tapped in the pipe the drilltap is drawn up, and the solid part of the slide G- (throughwhich the tap passed) is shifted over the hole thus tapped inthe packing piece H. By this means the water cannot escapewhen the spindle A and the drill tap B are removed. Thedrill tap is then taken from the socket of the spindle A andis replaced by a screw plug M, which projects below thesocket, and to the lower part of this is screwed the ferrule I,containing the plug valve. The spindle, ferrule, and plug are