ipe and the machined iron joint of the
universal joint pipe. Again, the choice was as between lead and leadite
for the bell and spigot pipe.

Cast iron was selected because of the certainty of its long life, and
the bell and spigot pipe was selected on the basis of comparative costs
for pipe laid. The standard lead joint was chosen on the result of
tests. This cast-iron pumping main has a diameter of 12 in. throughout.

_Pipe Weights._--Makers of standard bell and spigot pipe urged the usual
heavy weights selected for municipal service and heavy water-hammer.
Three pressures, _viz_., 217, 260, and 304 lb., were used for the
division of pipe weights, on which the standard pipe-makers specified
shell thicknesses of 0.82, 0.89, and 0.97 in. Eliminating water-hammer
and adopting a working stress of 2,400 lb., the thicknesses are reduced
to 0.54, 0.65, and 0.76 in. To make the latter conform to the
specifications of the New England Water-Works Association, the pipe was
cast to 0.57, 0.65, and 0.77 in. The reduction in cost amounts to
$52,811.

By the provision of air-cushions, hereafter described, the writer's
anticipation of no water-hammer on the pumping main has been fully
realized.

The pipe was manufactured and inspected under the above-mentioned
specifications.

_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 t