uld be used a length of pipe having
a side branch, oblique to the direction of the flow, to receive such
connection. The location of these branches should be accurately
indicated on the plan; and they should be closed with a flat stone or a
bit of slate, well cemented in place.

It will at times be necessary to use larger conduits than even an
eight-inch pipe. Up to a diameter of fifteen inches, it is cheapest to
use pipes, but for eighteen inches or more, brick-work is cheaper; and
at that size--a considerable regular flow of water being insured--the
slight roughness of brick-work offers no serious objection. The use of
oval or egg-shaped sewers will rarely be necessary under the
circumstances that we are considering; but there may be exceptional
conditions where the covering-in of a brook, or storm-water course,
cannot be avoided; and in such cases the volume of water may vary so
greatly that there will at times be a mere thread of a stream, and at
times a torrent. Here the oval form is the best, as concentrating a
small flow within a narrow and deep channel, and still giving the
capacity needed for exceptionally large volumes. All bricks used for
sewers, man-holes, &c., should be of the very hardest quality, and true
in form. The general rule is to be kept in mind, that the thickness of
the wall of a brick sewer should not be less than one-ninth of the inner
diameter; that is to say, that up to a diameter of three feet the
thickness of the wall should equal the width of a brick,--four inches.
This applies to circular sewers only: the oval form, being less strong,
calls for a wall of a thickness equal to one-eighth of the largest
diameter.

Connecting drains leading from houses to the sewer are to be made at
private cost; but they should be made in accordance with plans furnished
by the public authority, and by a workman acceptable to that authority.

The householder might be permitted to take the responsibility of the
finishing of his drain, but for the fact that the working of the public
sewer calls for the largest amount of water in proportion to the amount
of solid matters that it is possible to secure, and thus makes it
imperative that this drain should be absolutely tight, so that the
liquid parts of the house outflow shall not trickle away through its
joints, leaving only the more solid parts to flow into the public sewer.

Properly graded and smoothly jointed, a four-inch pipe will carry more
water than ev