the same diameter, exactitude of
form was of more importance than smoothness of surface; that glass
pipes, which had a wavy surface, discharged less water, at the same
inclinations, than Staffordshire stone-ware clay pipes, which were
of perfectly exact construction. By passing pipes of the same
clay--the common red clay--under a second pressure, obtained by a
machine at an extra expense of about eighteen pence per thousand,
whilst the pipe was half dry, very superior exactitude of form was
obtained, and by means of this exactitude, and with nearly the same
diameters, an increased discharge of water of one-fourth was
effected within the same time."

So all sudden turns or angles increase friction and retard velocity, and
thus lessen the capacity of the drain--a topic which may be more
properly considered under the head of the junction of drains.

"On a large scale, it was found that when equal quantities of water
were running direct, at a rate of 90 seconds, with a turn at
right-angles, the discharge was only effected in 140 seconds;
whilst, with a turn or junction with a gentle curve, the discharge
was effected in 100 seconds."

We are indebted to Messrs. Shedd & Edson for the following valuable
tables showing the capacity of water-pipes, with the accompanying
suggestions:

"DISCHARGE OF WATER THROUGH PIPES.

"The following tables of discharge are founded on the experiments
made by Mr. Smeaton, and have been compared with those by Henry
Law, and with the rules of Weisbach and D'Aubuisson. The conditions
under which such experiments are made may be so essentially
different in each case, that few experiments give results
coincident with each other, or with the deductions of theory: and
in applying these tables to practice, it is quite likely that the
discharge of a pipe of a certain area, at a certain inclination,
may be quite unlike the discharge found to be due to those
conditions by this table, and that difference may be owing partly
to greater or less roughness on the inside of the pipe, unequal
flow of water through the joints into the pipe, crookedness of the
pipes, want of accuracy in their being placed, so that the fall may
not be uniform throughout, or the ends of the pipes may be shoved a
little to one side, so that the continuity of the channel is