Pipe Joints.—­There was a question about the reliability of the lead joint at 300 lb.  The writer had a section of 12-in. pipe, with standard joints containing 22 lb. of lead, laid and tested to 500 lb. without sign of failure or leakage.  The joints were caulked down 3/16 in. below the face of the bell.  Of 8,700 joints thus made in the field, not one has blown out or failed.  A few weeped slightly on top, and they were made permanently tight by additional caulking.  The present maximum pressure is 278 lb.  These joints are the standard joints specified by the New England Water-Works Association.  It should be borne in mind that there is no water-hammer on this line.  In 8,700 joints, 198,000 lb. of lead and 3,200 lb. of oakum were used, or 22.76 and 0.37 lb. per joint.

Leadite was tested in competition with lead, but it leaked at 100 lb. and failed under a sustained pressure of 300 lb.  It is a friable material, and cannot be caulked successfully.  Its principal ingredient appears to be sulphur.  The failure was by slow creeping out of the joints.  It is melted and poured, but not caulked.  It has attractive features for low pressures and for lines not subject to movement or heavy jarring.

Air-Cushions.—­To prevent water-hammer on the pumping main, all pumps are provided with large air-chambers.  In addition, and as the special feature for absorbing the shock of pumping under high pressure through a pipe 21 miles long, a large air-chamber in the form of a closed steel cylinder, 5 ft. in diameter and 15 ft. long, is mounted on the pumping main outside of the pump-house.  This cylinder is set on its side, in concrete collars, directly over the pipe beneath, to which it is connected by a 12-in. tee, in which a 12-in. gate-valve is set.  The cylinder is provided with a glass gauge, cocks, etc.  It was designed for a working pressure of 300 lb., and, at each pumping plant, it has proved to be entirely air-and water-tight.  As indicated by sensitive gauges on the pump main, just beyond these large air-chambers, the latter absorb all the water-hammer which gets beyond the air-chamber on the pumps.

Air-Pumps.—­Each pumping plant is provided with four automatic air-charging devices, connecting to all air-chambers of the pumps and to the air-chamber on the pumping main.  They are of the Nordberg type, and have proved very efficient.  They are operated only a part of the time; otherwise, they accumulate too much air in the chambers.

Air-Valves.—­On the entire line there are 144 automatic air-valves made by the United States Metal Manufacturing Company, of Berwick, Pa.  They are working satisfactorily.